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1
Smith, Jennifer Marie. "Characterization of host-bacteria interactions contributing to group B streptococcus colonization." Huntington, WV : [Marshall University Libraries], 2002. http://www.marshall.edu/etd/descript.asp?ref=64.
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Yang, Qian. "Proteomic investigation of the group B streptococcus." Thesis, Northumbria University, 2011. http://nrl.northumbria.ac.uk/2119/.
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The Group B Streptococcus (GBS) is a Gram-positive opportunistic pathogen which is a leading cause of neonatal disease globally. In 2000-2001, the general incidence of neonatal GBS infection was 0.72 per 1000 live births in U.K. and the mortality rate is about 10%, because of which neonatal GBS disease is a significant burden on society. GBS is part of the commensal flora, colonising the vagina and gastrointestinal tract of women. Vertical transmission is the main cause of early onset GBS disease. During the process of GBS neonatal disease, GBS must be able to survive in several very different host environments, including the vagina, amniotic fluid, the neonate's lung and blood. The vagina is normally acidic, low oxygen and with limited nutrients while the neonate's lung and blood are neutral, high oxygen and with abundant nutrient. Proteomic investigations of GBS protein expression under conditions representing those associated with benign maternal colonisation and foetal exposure may help us understand the molecular basis of GBS virulence. GBS growth characteristics, long term survival, acid adaptation, viable but non-culturable state and biofilm formation were investigated to help us understand how GBS survives in different environments and also help us to develop an in vitro model to reflect in vivo conditions during GBS disease development. An in vitro model of GBS growth under conditions reflecting maternal vaginal carriage (low pH, low oxygen, nutrient stress) and exposure to body fluids during invasive disease (neutral pH, aeration, nutrient sufficient) was established. Proteins expressed under each growth conditions were separated by two dimensional electrophoresis. Individual proteins were subjected to in-gel trypsin digestion and identified using liquid chromatography-mass spectrometry with peptide mass fingerprinting followed with bioinformatic research. A total of 76 proteins were identified and 16 of these were expressed differentially. The putative virulence factor C protein β antigen and proteins involved in responses to oxidative stress were up-regulated under the conditions reflecting neonatal exposure. Another in vitro model of GBS growth on Todd Hewitt agar in the presence or absence of 10% human serum was established and followed by proteomic investigation of proteins differentially expressed under these two conditions, as this model reflects GBS neonatal septicaemia (exposure to serum). A total of 84 proteins were identified and 11 of which were expressed differentially. The putative virulence factor C protein β antigen, arginine deiminase, an ABC transporter substrate-binding protein and glyceraldehyde-3-phosphate dehydrogenase were up-regulated in the presence of human serum.
3
Jones, Nicola. "A molecular epidemiological investigation of group B streptococcus." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402623.
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A multilocus sequence typing (MLST) system for group B streptococcus (GBS) has been developed and validated on a global collection of human GBS strains isolated from carriage and invasive disease. A carriage study was performed, over a 3-year period, to establish the rate of carriage ofGBS in pregnant women in Oxford, UK. Invasive isolates were collected, prospectively and retrospectively over a similar time period. Twenty-one percent of women studied were asymptomatic carriers of GBS. The incidence of invasive GBS was 0.9/1000 live births in neonates and 6.11100,000 population >60 years. The population structure of GBS is best depicted. using MLST. as a network of related clusters indicating the presence of recomb inationa I events occurring in the population that interfere with a tree like branching structure of the population. A single hypervirulent clone ofGBS (ST-17 complex) is responsible for an excess of neonatal disease in Oxford (odds ratio 3.4). The possibility that a factor other than capsular type IIImay be responsible for virulence of this clonal complex in neonates is raised. Intriguingly this clonal complex was unique among human lineages in that it has emerged from bovine GBS. It was not however associated with increased invasiveness amongst adult (> 60 years). Further study ofthis hypervirulent clone of GBS is likely to contribute to the understanding of the pathogenesis of neonatal GBS disease.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1248526.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263953.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1264013.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263915.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1264035.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1248546.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263975.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263893.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265353.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1248470.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265253.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1266678.
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GIUSSANI, STEFANIA. "Mechanisms of Complement evasion in Group B Streptococcus." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265273.
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Kong, Fanrong. "Integrated study of group B streptococcus and human ureaplasmas : the paradigm shifts." Thesis, The University of Sydney, 2004. http://hdl.handle.net/2123/592.
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Group B streptococcus (GBS, S. agalactiae) and human ureaplasmas (U. parvumand U. urealyticum) are two clinically and phylogenetically related, potential perinatal pathogens. Their relationships between genotypes and pathogenesis of GBS and ureaplasma infection were still not well understood, one of the reason is that both of them are still short of a very practical genotyping system. In the study, to solve the above problem we developed genotyping systems for the organisms (the second section). For human ureaplasmas, based on four genes/gene clusters (rRNAgene clusters, the elongation factor Tu genes, urease gene complexes and multiplebanded antigen genes), we designed many primer pairs suitable for developing species identification assays for the two newly established human ureaplasma species (U. parvum and U. urealyticum). Further, based on the heterogeneity of ureaplasma multiple banded antigen gene (which contains species- and serovar-specific regions), we developed genotyping methods for each ureaplasma species.For GBS, based on three sets of molecular markers (capsular polysaccharidesynthesis gene clusters, surface protein antigen genes and mobile genetic elements),we developed a genotyping system. The primary evaluation of the genotyping systems showed that the genotyping systems were practical alternative assays for the conventional serotyping and they will be useful to further explore the relationships between genotypes and pathogenesis of GBS and ureaplasma infection. In the study, we introduced novel data and tools into GBS and ureaplasma studies especially from genomic- and bioinformatics-based molecular microbiology(the third section). For two newly established human ureaplasma species, based on the U. parvum serovar-3 genome, and using the above four important genes/geneclusters, we exposed some interesting problems in the understanding of newureaplasma taxonomy especially in the post genomic era. For GBS, we studied the two published full genomes and exposed some new problems or possible future new research fields. In particular we found the two finished and one ongoing GBS genomes were all non-typical and suggest that future genomic project had better have genetic population structure viewpoint. Finally, we suggested that integrated studies of the two potential or conditional perinatal pathogens, from the viewpoint of evolution, would provide a new understanding angle of the pathogenesis of the two organisms. Studies suggested that during coevolution, human ureaplasmas(especially U. parvum) became friendlier than their ancestors to their human host (by losing most of its virulence genes); however, GBS tried to increase its invasive abilities (by getting more virulence genes) to fight against the human host attack.
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Kong, Fanrong. "Integrated study of group B streptococcus and human ureaplasmas � the paradigm shifts." University of Sydney. Medicine, 2004. http://hdl.handle.net/2123/592.
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Group B streptococcus (GBS, S. agalactiae) and human ureaplasmas (U. parvumand U. urealyticum) are two clinically and phylogenetically related, potential perinatal pathogens. Their relationships between genotypes and pathogenesis of GBS and ureaplasma infection were still not well understood, one of the reason is that both of them are still short of a very practical genotyping system. In the study, to solve the above problem we developed genotyping systems for the organisms (the second section). For human ureaplasmas, based on four genes/gene clusters (rRNAgene clusters, the elongation factor Tu genes, urease gene complexes and multiplebanded antigen genes), we designed many primer pairs suitable for developing species identification assays for the two newly established human ureaplasma species (U. parvum and U. urealyticum). Further, based on the heterogeneity of ureaplasma multiple banded antigen gene (which contains species- and serovar-specific regions), we developed genotyping methods for each ureaplasma species.For GBS, based on three sets of molecular markers (capsular polysaccharidesynthesis gene clusters, surface protein antigen genes and mobile genetic elements),we developed a genotyping system. The primary evaluation of the genotyping systems showed that the genotyping systems were practical alternative assays for the conventional serotyping and they will be useful to further explore the relationships between genotypes and pathogenesis of GBS and ureaplasma infection. In the study, we introduced novel data and tools into GBS and ureaplasma studies especially from genomic- and bioinformatics-based molecular microbiology(the third section). For two newly established human ureaplasma species, based on the U. parvum serovar-3 genome, and using the above four important genes/geneclusters, we exposed some interesting problems in the understanding of newureaplasma taxonomy especially in the post genomic era. For GBS, we studied the two published full genomes and exposed some new problems or possible future new research fields. In particular we found the two finished and one ongoing GBS genomes were all non-typical and suggest that future genomic project had better have genetic population structure viewpoint. Finally, we suggested that integrated studies of the two potential or conditional perinatal pathogens, from the viewpoint of evolution, would provide a new understanding angle of the pathogenesis of the two organisms. Studies suggested that during coevolution, human ureaplasmas(especially U. parvum) became friendlier than their ancestors to their human host (by losing most of its virulence genes); however, GBS tried to increase its invasive abilities (by getting more virulence genes) to fight against the human host attack.
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Rego, Sara. "Molecular basis of group B streptococcus pathogenesis and colonisation." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702432.
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Streptococcus agalactiae (Group B Streptococcus, GBS) is a cause of life-threatening infections in neonates and in the elderly. Clinical presentations of GBS disease include sepsis, pneumonia and meningitis. GBS normally resides as a commensal microorganism of the female genitourinary tract, where it can be vertically transmitted to the foetus/neonate in utero or during parturition. The oropharynx also represents an important point of entry for GBS in both neonates and adults. GBS is thus able to adhere to a variety of host tissues, including epithelia of the vagina, lung or meninges. These interactions are primarily mediated by cell surface proteins that recognise specific host receptors. This study investigated a family of putative GBS adhesins designated Group B streptococcal proteins (Bsp). Bsp proteins belong to the antigen I/II (AgI/II) polypeptide family, which are multifunctional adhesins found across the Streptococcus genus. It was hypothesised that Bsp proteins function as colonisation determinants of GBS. Bsp proteins were shown to promote binding to factors relevant to colonisation of vaginal or oral niches, including human vaginal epithelium, scavenger receptor glycoprotein-340 and to the resident microbiota member Candida albicans. Complementary structural characterisation of dissected domains of the prototypical Bsp family member, BspA, revealed structural features not previously reported in AgI/II family polypeptides. This suggested that the mechanism of Bsp-mediated receptor engagement might be distinct from that of other AgI/II family members. Collectively, the results of this study identified Bsp family proteins as novel adhesins that provide potential competitive advantage in GBS colonisation and pathogenesis. A better understanding of the molecular mechanisms involved in bacterial colonisation will assist development of new clinical interventions against GBS disease.
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Ng, Sherrianne Qin Yin. "Preterm infant IFN-Beta responses to Group B streptococcus." Thesis, Ng, Sherrianne Qin Yin (2013) Preterm infant IFN-Beta responses to Group B streptococcus. Honours thesis, Murdoch University, 2013. https://researchrepository.murdoch.edu.au/id/eprint/17002/.
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Group B streptococcus (GBS) is the leading cause of early onset sepsis in preterm infants. The production of IFN-Beta shown to be critical for host defense against GBS in murine studies. The release of GBS-DNA into the cytosol of mouse macrophages was found to induce IFN-Beta monocytes and macrophages produce IFN-Beta GBS-DNA plays in this process. This study optimised a whole blood assay to determine if human monocyte subsets are capable of inducing IFN-Beta as cytosolic GBS-DNA. The main findings were that (A) all adult blood monocyte subsets were capable of producing IFN-Beta cytosolic GBS-DNA, as determined by IP-10 expression, (B) the intermediate monocyte subset produced the highest amount of IP-10 to both live GBS and cytosolic GBS-DNA, and (C) the monocytes of a preterm infant had similar IP- 10 responses to cytosolic GBS-DNA but much lower IP-10 responses to live GBS compared to adults. These findings indicate that human blood monocytes are capable of producing IFN-
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Lazzarin, Maddalena <1986>. "Structural and functional characterization of Group B Streptococcus pilus 2b." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6815/1/lazzarin_maddalena_tesi.pdf.
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Group B Streptococcus (GBS) is a Gram-positive human pathogen representing one of the most common causes of life-threatening bacterial infections such as sepsis and meningitis in neonates. Covalently polymerized pilus-like structures have been discovered in GBS as important virulence factors as well as vaccine candidates. Pili are protein polymers forming long and thin filamentous structures protruding from bacterial cells, mediating adhesion and colonization to host cells. Gram-positive bacteria, including GBS, build pili on their cell surface via a class C sortase-catalyzed transpeptidation mechanism from pilin protein substrates that are the backbone protein forming the pilus shaft and two ancillary proteins. Also the cell-wall anchoring of the pilus polymers made of covalently linked pilin subunits is mediated by a sortase enzyme. GBS expresses three structurally distinct pilus types (type 1, 2a and 2b). Although the mechanisms of assembly and cell wall anchoring of GBS types 1 and 2a pili have been investigated, those of pilus 2b are not understood until now. Pilus 2b is frequently found in ST-17 strains that are mostly associated with meningitis and high mortality rate especially in infants.
In this work the assembly mechanism of GBS pilus type 2b has been elucidated by dissecting through genetic, biochemical and structural studies the role of the two pilus-associated sortases. The most significant findings show that pilus 2b assembly appears “non-canonical”, differing significantly from current pilus assembly models in Gram-positive pathogens. Only sortase-C1 is involved in pilin polymerization, while the sortase-C2 does not act as a pilin polymerase, but it is involved in cell-wall pilus anchoring. Our findings provide new insights into pili biogenesis in Gram-positive bacteria. Moreover, the role of this pilus type during host infection has been investigated. By using a mouse model of meningitis we demonstrated that type 2b pilus contributes to pathogenesis of meningitis in vivo.
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Lazzarin, Maddalena <1986>. "Structural and functional characterization of Group B Streptococcus pilus 2b." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6815/.
Full textAbstract:
Group B Streptococcus (GBS) is a Gram-positive human pathogen representing one of the most common causes of life-threatening bacterial infections such as sepsis and meningitis in neonates. Covalently polymerized pilus-like structures have been discovered in GBS as important virulence factors as well as vaccine candidates. Pili are protein polymers forming long and thin filamentous structures protruding from bacterial cells, mediating adhesion and colonization to host cells. Gram-positive bacteria, including GBS, build pili on their cell surface via a class C sortase-catalyzed transpeptidation mechanism from pilin protein substrates that are the backbone protein forming the pilus shaft and two ancillary proteins. Also the cell-wall anchoring of the pilus polymers made of covalently linked pilin subunits is mediated by a sortase enzyme. GBS expresses three structurally distinct pilus types (type 1, 2a and 2b). Although the mechanisms of assembly and cell wall anchoring of GBS types 1 and 2a pili have been investigated, those of pilus 2b are not understood until now. Pilus 2b is frequently found in ST-17 strains that are mostly associated with meningitis and high mortality rate especially in infants.
In this work the assembly mechanism of GBS pilus type 2b has been elucidated by dissecting through genetic, biochemical and structural studies the role of the two pilus-associated sortases. The most significant findings show that pilus 2b assembly appears “non-canonical”, differing significantly from current pilus assembly models in Gram-positive pathogens. Only sortase-C1 is involved in pilin polymerization, while the sortase-C2 does not act as a pilin polymerase, but it is involved in cell-wall pilus anchoring. Our findings provide new insights into pili biogenesis in Gram-positive bacteria. Moreover, the role of this pilus type during host infection has been investigated. By using a mouse model of meningitis we demonstrated that type 2b pilus contributes to pathogenesis of meningitis in vivo.
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Hull, James Richard. "The interactions of group B Streptococci with human fibronectin /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9917.
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Varghese, Brian R. "Characterising the Antimicrobial Effect of Zinc Intoxication in Group B Streptococcus." Thesis, Griffith University, 2023. http://hdl.handle.net/10072/421271.
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Group B Streptococcus (GBS) is a Gram-positive bacteria known for causing a wide range of illnesses in neonates, pregnant woman, elderly, and immunocompromised people. Intrapartum antibiotic prophylaxis is the current prevention measure for pregnant women used worldwide and has been highly successful thus far. However, it is a dangerous long-term approach with the rising antimicrobial resistance crisis. Vaccine development has been ongoing for several decades and remains a key area of study for GBS researchers worldwide. Finding an effective vaccine target candidate that can be packaged in a safe and inexpensive manner is a continuous challenge.
The use of metal ions, such as zinc, as an antibacterial has dated back centuries. Its potential to be harnessed against GBS shows promise as an alternative treatment and prevention option, leading to recent characterisation of GBS zinc efflux machinery. It has been established that GBS employs robust strategies to overcome zinc stress and mediate survival. While bacteria require essential nutrient metals for survival, it is presented with nutritional challenges imposed by the vertebrate host during infection. One such strategy is intoxication of invading bacterial pathogens with transition metals.
This work assessed 16 strains of GBS from diverse capsular serotypes, sequence types and isolation sources for susceptibility or resistance toward zinc intoxication. The findings show that strains of a variety of clinical backgrounds, capsular types and sequence-types differ in their resistance phenotypes toward zinc intoxication. For example, cpsV and ST-19 were found to be highly resistant to zinc stress, whereas cpsIII and ST-7 and ST-17 were most sensitive to metal intoxication. It is also first reported here that IS1381, a previously identified transposon, has been found in the main zinc export gene, czcD, of strain 834. Investigation of its possible involvement in strain 834’s increased resistance phenotype was inconclusive.Thesis (Masters)
Master of Medical Research (MMedRes)
School of Pharmacy & Med Sci
Griffith Health
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Seedat, Farah. "Universal antenatal screening for group B streptococcus colonisation in the UK." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/103062/.
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Background: Group B Streptococcus (GBS) is the leading cause of neonatal sepsis and meningitis. Currently, the UK recommends against universal antenatal screening to prevent early-onset GBS disease (EOGBS, < 7 days). Key gaps around GBS natural history, harms from screening and a lack of high-quality data to prove screening effectiveness make it difficult to ensure the benefits of GBS screening outweigh the harms. There is also a wider gap on policy-making processes for screening. The overall aim of this thesis is to address these gaps and examine whether the UK should introduce universal GBS screening as a result. Methods: In addition to a literature review, I used two approaches: systematic review/metaanalysis and ecological trend analysis. The systematic reviews synthesised evidence on the screening policy-making processes, mechanisms of EOGBS and adverse events from intrapartum antibiotic prophylaxis (IAP) to prevent EOGBS. In the absence of RCTs, I combined ecological data on the benefits and harms of GBS screening, then analysed their trends across time compared with other prevention strategies in regression analyses adjusting for context differences. Results: Evidence from 17 countries showed that most GBS screening recommendations were not developed by screening organisations and it is not known whether screening principles and the likely unseen harms of GBS screening were considered. Seventeen studies revealed that we do not fully understand the natural history of why some mothers, but not others, transmit GBS to their neonates, or which neonates will develop EOGBS. There was consistent evidence that heavy bacterial load was associated with transmission and progression to EOGBS. Neonates colonised with serotype III were also twice as likely to develop EOGBS compared with serotype Ia and II. However, the evidence was old and at high risk of bias. The selective culture test at 35 to 37 weeks gestation is not an accurate predictor of EOGBS and at least 99% of screen-positive and treated mothers (and their neonates) would be over-treated. Seventeen observational studies and 13 RCTs showed a wide range of potential harms from IAP, including cerebral palsy, functional impairment and antibiotic resistance. However, there was little high-quality and applicable evidence to quantify the frequency of adverse events. The three ecological trend analyses combining data from 59 geographical areas showed that EOGBS incidence decreased by approximately 0.02 per 1,000 livebirths per year in areas that most recently reported GBS screening, whereas it increased by approximately 0.01 to 0.02 per 1,000 livebirths in areas most recently reporting risk-based prevention. Areas that recently did not have GBS prevention displayed conflicting EOGBS trends. By contrast, there was no evidence that screening impacted annual early-onset sepsis trends compared with other, or no prevention strategies; however, this study did not have a sufficient sample size. The was no harmful impact of GBS screening on LOGBS trends compared with other, or no prevention. There was also no evidence that screening increased early-onset E. coli incidence and the percentage of GBS cases resistant to clindamycin and erythromycin, compared with risk-based or no prevention; again, these analyses did not have a sufficient sample size. The findings of these studies must be treated with caution as some results may be due to low statistical power and others were unstable across analyses. The findings also contain numerous limitations as covariates were poorly collected in most countries. Therefore, the evidence on the benefits and harms of universal GBS screening remains inconclusive. Conclusion: GBS infection is an important health condition and its persistence, poor screening tests and the IAP harms stress the need for a better understanding of the natural history of GBS and more effective prevention. Evidence on the harms and benefits of GBS screening is limited, therefore, screening should not be introduced in the UK. Ecological trend analysis was not an adequate method to inform GBS screening decisions, however, it may be useful for screening decisions on other conditions.
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Cozzi, Roberta <1981>. "Structural and functional characterization of Group B Streptococcus class C sortases." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3522/1/Cozzi_Roberta_tesi.pdf.
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In Group B Streptococcus (GBS) three structurally distinct types of pili have been discovered as potential virulence factors and vaccine candidates. The pilus-forming proteins are assembled into high-molecular weight polymers via a transpeptidation mechanism mediated by specific class C sortases. Using a multidisciplinary approach including bioinformatics, structural and biochemical studies and in vivo mutagenesis we performed a broad characterization of GBS sortase C. The high resolution X-ray structure of the enzymes revealed that the active site, located into the β-barrel core of the enzyme, is made of the catalytic triad His157-Cys219-Arg228 and covered by a loop, known as the “lid”. We show that the catalytic triad and the predicted N- and C-terminal trans-membrane regions are required for the enzyme activity. Interestingly, by in vivo complementation mutagenesis studies we found that the deletion of the entire lid loop or mutations in specific lid key residues had no effect on catalytic activity of the enzyme. In addition, kinetic characterizations of recombinant enzymes indicate that the lid mutants can still recognize and cleave the substrate-mimicking peptide at least as well as the wild type protein.
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Cozzi, Roberta <1981>. "Structural and functional characterization of Group B Streptococcus class C sortases." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3522/.
Full textAbstract:
In Group B Streptococcus (GBS) three structurally distinct types of pili have been discovered as potential virulence factors and vaccine candidates. The pilus-forming proteins are assembled into high-molecular weight polymers via a transpeptidation mechanism mediated by specific class C sortases. Using a multidisciplinary approach including bioinformatics, structural and biochemical studies and in vivo mutagenesis we performed a broad characterization of GBS sortase C. The high resolution X-ray structure of the enzymes revealed that the active site, located into the β-barrel core of the enzyme, is made of the catalytic triad His157-Cys219-Arg228 and covered by a loop, known as the “lid”. We show that the catalytic triad and the predicted N- and C-terminal trans-membrane regions are required for the enzyme activity. Interestingly, by in vivo complementation mutagenesis studies we found that the deletion of the entire lid loop or mutations in specific lid key residues had no effect on catalytic activity of the enzyme. In addition, kinetic characterizations of recombinant enzymes indicate that the lid mutants can still recognize and cleave the substrate-mimicking peptide at least as well as the wild type protein.
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Prince, Darren William. "The Co-Transcriptional Response of Intracellular Group B Streptococcus (GBS) and Monocytes." Thesis, Griffith University, 2019. http://hdl.handle.net/10072/389087.
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Group B Streptococcus (GBS) is a species of gram positive bacteria representing a significant human pathogen; namely, as the most prolific cause of neonatal disease and mortality globally, but also increasingly reported in adult disease (especially among the elderly and those with compromised immune systems). The first chapter of this thesis reviews the extensive literature covering GBS; with a focus on classification and disease. Selected virulence factors are also discussed. In chapter 2, eight strains of GBS were selected for whole genome sequencing by Third Generation, Pacific Biosystems (PacBio) sequencing technology. A protocol was optimised to provide sufficient, high quality genomic preparations from multiple strains of GBS – suitable for the PacBio technology. Using a sequenced strain of GBS from chapter 2, an infection model was optimised in chapter 3 for the purpose of providing quality RNA for co-transcript analysis. U937 human monocytes were infected with GBS (strain 874391) and the host/pathogen RNA prepared from the same reaction (monocytes with internalised GBS) – with an emphasis on yielding sufficient pathogen RNA; which can sometime be an impediment for co-transcript studies. Pathogen RNA derived from the optimised infection protocol was demonstrated to amplify with RT-qPCR for 12 tested GBS genes (cylE, 1010, rib, czcD, pil2B, cpsE, scpB, htp, cfb, copA, hvgA and maeA). In chapter 4, RT-qPCR was used to analyse differential gene expression from the mixed, host/pathogen RNA. Twelve human genes and 12 GBS genes were assessed for differential gene expression. Seven of the tested human genes (IL8, IL1A, IL1B, IL10, TNF, LMO2 and MCP-1) and 6 of the tested GBS genes (scpB, 1010, rib, czcD, htp, hvgA) were significantly upregulated in RNA derived from the infection samples. Of the GBS genes tested, htp was the most upregulated. An htp knockout mutant of GBS strain 874391 (Δhtp) was constructed for chapter 5 of this thesis to assess the impact of htp transcription on GBS survival in an infection context. The infection assays optimised in chapter 3 were performed with the Δhtp GBS construct. Contrary to expectation, the Δhtp GBS construct survived the internalised environment of the monocytes in significantly higher numbers than the wild-type over 48 hours of infection.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Medical Science
Griffith Health
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Zerbini, Francesca <1982>. "Polymerizing activity and regulation of group B Streptococcus pilus 2a sortase C1." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6480/1/Zerbini_Francesca_tesi.pdf.
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Group B Streptococcus [GBS; Streptococcus agalactiae] is the leading cause of life-threatening diseases in newborn and is also becoming a common cause of invasive diseases in non-pregnant, elderly and immune-compromised adults. Pili, long filamentous fibers protruding from the bacterial surface, have been discovered in GBS, as important virulence factors and vaccine candidates. Gram-positive bacteria build pili on their cell surface via a class C sortase-catalyzed transpeptidation mechanism from pilin protein substrates. Despite the availability of several crystal structures, pilus-related C sortases remain poorly characterized to date and their mechanisms of transpeptidation and regulation need to be further investigated. The available three-dimensional structures of these enzymes reveal a typical sortase fold except for the presence of a unique feature represented by an N-terminal highly flexible loop, known as the “lid”. This region interacts with the residues composing the catalytic triad and covers the active site, thus maintaining the enzyme in an auto-inhibited state and preventing the accessibility to the substrate. It is believed that enzyme activation may occur only after lid displacement from the catalytic domain. In this work we provide the first direct evidence of the regulatory role of the lid, demonstrating that it is possible to obtain in vitro an efficient polymerization of pilin subunits using an active C sortase lid mutant carrying a single residue mutation in the lid region. Moreover, biochemical analyses of this recombinant mutant reveal that the lid confers thermodynamic and proteolytic stability to the enzyme. A further characterization of this sortase active mutant showed promiscuity in the substrate recognition, as it is able to polymerize different LPXTG-proteins in vitro.
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Zerbini, Francesca <1982>. "Polymerizing activity and regulation of group B Streptococcus pilus 2a sortase C1." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6480/.
Full textAbstract:
Group B Streptococcus [GBS; Streptococcus agalactiae] is the leading cause of life-threatening diseases in newborn and is also becoming a common cause of invasive diseases in non-pregnant, elderly and immune-compromised adults. Pili, long filamentous fibers protruding from the bacterial surface, have been discovered in GBS, as important virulence factors and vaccine candidates. Gram-positive bacteria build pili on their cell surface via a class C sortase-catalyzed transpeptidation mechanism from pilin protein substrates. Despite the availability of several crystal structures, pilus-related C sortases remain poorly characterized to date and their mechanisms of transpeptidation and regulation need to be further investigated. The available three-dimensional structures of these enzymes reveal a typical sortase fold except for the presence of a unique feature represented by an N-terminal highly flexible loop, known as the “lid”. This region interacts with the residues composing the catalytic triad and covers the active site, thus maintaining the enzyme in an auto-inhibited state and preventing the accessibility to the substrate. It is believed that enzyme activation may occur only after lid displacement from the catalytic domain. In this work we provide the first direct evidence of the regulatory role of the lid, demonstrating that it is possible to obtain in vitro an efficient polymerization of pilin subunits using an active C sortase lid mutant carrying a single residue mutation in the lid region. Moreover, biochemical analyses of this recombinant mutant reveal that the lid confers thermodynamic and proteolytic stability to the enzyme. A further characterization of this sortase active mutant showed promiscuity in the substrate recognition, as it is able to polymerize different LPXTG-proteins in vitro.
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SINGH, MEENAKSHI. "Synthesis of Group B Streptococcus tipe II (GBSII) Oligosaccharide of Vaccine Development." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/680023.
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Carbohydrates are among the most abundant molecules found on the cell surfaces of bacteria, parasites, and viruses. Apart from the conventional roles of carbohydrates as energy sources and structural polymers, carbohydrates are also associated with cancer metastasis, protein stabilization, pathogen infection and the immune response. Cells of our body have sensors made out of carbohydrates on outer surface of plasma membrane and acts as sensors and can detect many kinds of stimuli, and can signal the immune system to respond. Carbohydrate-protein molecular recognition processes have pivotal roles in infections and in immune response to pathogens. To date, several vaccines based on isolated capsular polysaccharides (CPSs) are marketed against infectious diseases. However, the use of isolated capsular polysaccharide poses several limitations, as natural sources are generally limited and the isolation is very challenging. Additionally, the isolated polysaccharides are heterogeneous and often contains impurities. Furthermore, limited protection of certain CPS antigens impairs the efficiency of vaccines. To overcome limitations associated with isolated polysaccharides, synthetic oligosaccharides present an effective alternative with great potential to understand glycan immunology and rationally design effective antigens. Consequently, characterization and reconstruction of carbohydrate epitopes with authentic composition has become one of the major target in glycoscience. To this end, strategies are needed to facilitate the streamlined design and generation of these antigens.
This thesis concerns the development of an effective synthetic strategy to obtain Group B Streptococcus (GBS) type II oligosaccharide for vaccine development. GBS, a Gram-positive bacterium, inhabits the intestinal and genitourinary tract of 10‐30% of humans. GBS is one of the primary causes of bacterial infections among neonates and pregnant women, resulting in many severe diseases such as sepsis, meningitis, abortion, and so on. Type II GBS is one of the predominant GBS serotypes and is associated with about 15% of the invasive infections in adults and infants; therefore, represents an important human pathogen. The development of effective preventive vaccine against GBS is much needed to help pregnant women protect their newborns. This thesis describes the effective synthetic strategy to synthesize GBS type II oligosaccharide to be applied for vaccine development.
Herein, we present a new and convenient synthesis of the repeating unit of GBS type II capsular polysaccharide. The structure of GBS type II was elucidated in 1983 and the repeating unit of GBS type II is a heptasaccharide composed of α-Neu5Ac (2-3)-ß-D-Gal-(1-4)- ß-D-GlcNAc-(1-3)-[-ß-D-Gal-(1-6)]-ß-D-Gal-(1-4)-ß-D-Gal-(1-3)-ß-D-Glc. The presented synthetic strategy is based on the five subcomponents derived from the retro synthetic analysis. Suitably protected lactosamine and lactose derivatives are pivotal building blocks in our synthesis and both disaccharide fragments have been achieved from the cheap and readily available lactose. Having started from two disaccharides saves the efforts of glycosylation and reduces the number of synthetic steps. The building blocks have been obtained in good overall yield following the optimized synthetic approach. The synthesis of backbone linear chain trisaccharide [ß-D-Gal-(1-4)-ß-D-Gal-(1-3)-ß-D-Glc] and pentasaccharide [ß-D-Gal-(1-4)-ß-D-GlcNAc-(1-3)-ß-D-Gal-(1-4)-ß-D-Gal-(1-3)-ß-D-Glc] has been achieved in excellent yield (~80% yield). The final steps of the synthesis comprise- the incorporation of ß-D-Gal unit into the linear chain pentasaccharide (currently ongoing) followed by the enzymatic introduction of sialic acid (NeuNAc unit) and subsequent deprotection to yield the repeating unit of GBS type II capsular polysaccharide.
To conclude, in this thesis we present an efficient and easy handling synthetic approach to the heptasaccharide repeating unit of GBS type II. Readily available and cheap dairy side-product lactose has been used as a key structure in the presented scheme, allowing the efficient synthesis of the pentasaccharide backbone of the target compound. The synthetic GBS II fragments will be used for glycan array and structural studies and immunochemical characterization with specific monoclonal antibodies.
This thesis comprises of four main chapters and the experimental section containing the methods and synthetic procedures for the discussed schemes. Chapter one is a general introduction and deals with the necessity and the social importance of the described project.
Chapter two of the thesis outlines the scientific background and pathogenesis of GBS, carbohydrates and their biological importance, and general introduction of vaccines and how the carbohydrates can be used as a suitable vaccine candidate. Chapter two establishes the importance of synthetic carbohydrates and how the synthetic carbohydrates can be used to develop suitable effective vaccines against GBS diseases.
Chapter three of the thesis contains the general introduction and structural features of GBS II CPS and the retrosynthetic analysis of GBS II CPS to identify the building blocks for the synthesis of GBS CPS II.
Chapter four of the thesis summarizes the synthetic strategies and results to achieve the building blocks described in chapter three and the recombination of fragments to achieve the final molecule GBS II CPS repeating unit.
The last part of the thesis will consists of the experimental methods and synthetic procedures to achieve the proposed molecule along with the characterization data.
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Santos, Almeida Alexandre Miguel. "Evolutionary insights into the host--specific adaptation and pathogenesis of group B Streptococcus Persistence of a dominant bovine lineage of group B Streptococcus reveals genomic signatures of host adaptation Whole-Genome Comparison Uncovers Genomic Mutations between Group B Streptococci Sampled from Infected Newborns and Their Mothers." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066029/document.
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Streptococcus agalactiae (streptocoque du groupe B, SGB) est un commensal fréquent des voies intestinale et génito-urinaire dans la population humaine mais constitue une des causes principales d'infections néonatales. Dans le même temps, SGB est connu comme pathogène vétérinaire, responsable de mastites bovines à l'origine de pertes économiques importantes dans plusieurs pays comme le Portugal. L'objectif de ma thèse était d'analyser au niveau génomique les bases de l'adaptation spécifique de SGB à ses hôtes humains et bovins et de l'établissement des lignées plus pathogènes. La comparaison des profils génomiques des souches isolées de nouveau-nés infectés et de leurs mères nous a permis de montrer que la transmission de SGB de mère à enfant est accompagnée dans certains cas par l'acquisition de mutations pathoadaptives. Par ailleurs, l'analyse des séquences génomiques de plus de 600 souches appartenant au complexe clonal (CC) 17, hypervirulent et spécifique à l'hôté humain, nous a permis de caractériser les forces évolutives agissant sur ce complexe. Finalement, l'étude de la colonisation des fermes laitières portugaises par un seul clone CC61 depuis plus de 20 ans a mis en évidence que la régulation spécifique de l'import du fer/manganèse est une stratégie d'adaptation récurrente dans l’environnement bovin. En conclusion, les résultats que nous présentons améliorent notre compréhension de l'adaptation chez les espèces hôte-généralistes, en apportant des idées utiles qui pourront spécifiquement aider à améliorer le contrôle et le traitement des infections de SGB mondialementStreptococcus agalactiae (group B Streptococcus, GBS) is a commensal of the intestinal and genitourinary tracts in the human population, while also a leading cause of neonatal infections. Likewise, GBS remains a serious concern in many countries as frequently responsible for bovine mastitis. Therefore, the purpose of my PhD project was to use state-of-the-art whole-genome approaches to decipher the host-specific adaptation and pathogenesis of GBS in both humans and bovines. By comparing the genomic profile of strains from infected newborns and their mothers we showed that the transmission of GBS from mother to child is accompanied in particular instances by the acquisition of specific pathoadaptive mutations. Moreover, from the study of the evolutionary forces acting on the human-specific and hypervirulent clonal complex (CC) 17, we reveal that various systems can evolve to improve the ability of GBS to survive in the human host. Functions related to metabolism, cell adhesion, regulation and immune evasion were among the most preferentially affected in GBS strains from human origin. Conversely, colonization of Portuguese dairy farms by one single CC61 clone for over 20 years highlighted that the specific regulation of iron/manganese uptake is a recurrent adaptive strategy in the bovine environment
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Siqueira, Fabio [UNESP]. "Colonização de pacientes grávidas por Streptococcus agalactiae em Taguatinga, Distrito Federal, Brasil." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/148701.
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Fundação de Ensino e Pesquisa em Ciências da Saúde (FEPECS)
Objetivo: verificar a prevalência do estreptococo do grupo B em gestantes de Taguatinga, Distrito Federal, Brasil. Desenho: Estudo transversal. Local: Taguatinga (Região metropolitana de Brasília), Distrito Federal, Brasil. Introdução: o estreptococo do Grupo B é responsável por infecções graves em neonatos, resultante da transmissão vertical por gestantes colonizadas nas regiões anal, perineal ou vaginal. A identificação das pacientes colonizadas e uso de profilaxia intraparto podem reduzir o risco de infeção neonatal Métodos: Estudo transversal em pacientes gestantes entre a 35 e 37ª. semana de gravidez. Foi coletado material das pacientes para identificação laboratorial do Estreptococo do grupo B. Também foram coletados dados epidemiológicos das pacientes como peso, altura, índice da massa corporal, uso de antibióticos durante a gravidez, comorbidades durante a gravidez (diabetes, doenças hipertensivas, hipotireoidismo), gemelaridade, entre outras. Resultados: a amostra foi composta de 501 gestantes e a prevalência para o estreptococo do grupo B foi de 14%. A média de idade foi de 29 anos e o índice de massa corporal de 30,7. Durante a gravidez 204 pacientes tiveram algum tipo de infecção e 201 foram usaram antibióticos, 95 foram diagnosticadas com diabetes melito gestacional e 74 com alguma doença hipertensiva. Conclusão: a prevalência encontrada não difere do verificado por outros autores. Dentre os fatores estudados nenhum manifestou-se como fator de risco ou de proteção para a colonização materna para o estreptococo do grupo B.
Objective: To verify the prevalence of group B streptococcus (GBS) in pregnant women in Taguatinga, Federal District, Brazil. Design: Cross-sectional study. Setting: Taguatinga (metropolitan region of Brasilia), Federal District, Brazil. Sample: 501 pregnant women Methods: This cross-sectional study was conducted in pregnant women between the 35th and 37th week of pregnancy. Samples were collected from patients for laboratory identification of GBS. Epidemiological data were also collected from patients, including weight, height, body mass index, use of antibiotics during pregnancy, pathologies during pregnancy (diabetes, hypertensive disease, hypothyroidism), and twin pregnancy. Main outcome measures: Presence or absence of GBS in pregnant women. Results: The sample was composed of 501 pregnant women, and the prevalence of GBS was 14%. The average age was 29 years, and the average body mass index was 30.7. During pregnancy, 204 patients had some kind of infection, 201 of them have used antibiotics, 95 were diagnosed with gestational diabetes mellitus, and 74 were diagnosed with some kind of hypertensive disease. Conclusion: The prevalence found does not differ from that verified by other authors. None of the studied factors was a risk or protection factor for maternal GBS colonization.
FEPECS: 064.000.052/2012
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Siqueira, Fabio. "Colonização de pacientes grávidas por Streptococcus agalactiae em Taguatinga, Distrito Federal, Brasil." Botucatu, 2017. http://hdl.handle.net/11449/148701.
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Orientador: Adriano DiasResumo: Objetivo: verificar a prevalência do estreptococo do grupo B em gestantes de Taguatinga, Distrito Federal, Brasil. Desenho: Estudo transversal. Local: Taguatinga (Região metropolitana de Brasília), Distrito Federal, Brasil. Introdução: o estreptococo do Grupo B é responsável por infecções graves em neonatos, resultante da transmissão vertical por gestantes colonizadas nas regiões anal, perineal ou vaginal. A identificação das pacientes colonizadas e uso de profilaxia intraparto podem reduzir o risco de infeção neonatal Métodos: Estudo transversal em pacientes gestantes entre a 35 e 37ª. semana de gravidez. Foi coletado material das pacientes para identificação laboratorial do Estreptococo do grupo B. Também foram coletados dados epidemiológicos das pacientes como peso, altura, índice da massa corporal, uso de antibióticos durante a gravidez, comorbidades durante a gravidez (diabetes, doenças hipertensivas, hipotireoidismo), gemelaridade, entre outras. Resultados: a amostra foi composta de 501 gestantes e a prevalência para o estreptococo do grupo B foi de 14%. A média de idade foi de 29 anos e o índice de massa corporal de 30,7. Durante a gravidez 204 pacientes tiveram algum tipo de infecção e 201 foram usaram antibióticos, 95 foram diagnosticadas com diabetes melito gestacional e 74 com alguma doença hipertensiva. Conclusão: a prevalência encontrada não difere do verificado por outros autores. Dentre os fatores estudados nenhum manifestou-se como fator de risco ou de proteçã... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor
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Weiman, Shannon Dawn. "Sialic acid O-acetylation in group B Streptococcus impact on pathogen-host interactions /." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3369630.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed September 15, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Pomwised, Rattanaruji. "Studies of peptide mimicry of the group B Streptococcus type III capsular polysaccharide antigen." Diss., Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/pomwised/PomwisedR1207.pdf.
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Lewis, Amanda L. "Discovery, characterization and pathologic relevance of sialic acid O-acetylation in group B Streptococcus /." Diss., Connect to a 24 p. preview or request complete full text in PDF formate. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3238518.
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Hays, Constantin. "Influence de l'imprégnation hormonale périnatale sur la virulence du Streptocoque du groupe B Perinatal hormonal concentrations favor CC17 group B Streptococcus hypervirulence and intestinal translocation through M cells." Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2183&f=15494.
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Streptococcus agalactiae (streptocoque du groupe B, SGB) représente la première cause d'infections néonatales bactériennes invasives pour lesquelles on définit deux syndromes, un syndrome précoce (SP, 1ère semaine de vie) et un syndrome tardif (ST, 7 à 89 jours après la naissance). Le SP se manifeste par une pneumonie associée ou non à une bactériémie et résulte de l'inhalation par le nouveau-né de sécrétions vaginales ou de liquide amniotique contaminés par le SGB. Le ST se déclare par une septicémie dont la porte d'entrée serait le tractus gastro-intestinal et est caractérisé par un fort taux de méningite. Un clone désigné CC-17 est responsable de près de la moitié des SP et de 70% des ST et des méningites, alors qu'il n'est que rarement responsable d'infections chez l'adulte (15% des cas). L'hypervirulence du clone CC-17 a été attribuée à des capacités accrues de colonisation et de translocation du tube digestif, ainsi que de franchissement de la barrière hémato-encéphalique. Cependant, ces propriétés ne peuvent expliquer à elles seules son association aux infections néonatales et des facteurs liés à l'hôte sont probablement impliqués. Tout au long de la grossesse, le fœtus est exposé à des concentrations croissantes d'hormones stéroïdiennes maternelles, en particulier l'estradiol (E2) et la progestérone (P4). Ainsi, les taux du nouveau-né sont 500 fois supérieurs à ceux d'un homme adulte puis chutent drastiquement dans les trois premiers jours de vie et se stabilisent pour quelques mois à des taux 5 à 50 fois plus élevés que chez l'adulte. Or, ces hormones régulent de manière concentration dépendante la réponse immunitaire, la perméabilité des barrières cellulaires, et l'expression de molécules d'adhésion. Ainsi, l'imprégnation hormonale massive des nouveau-nés pourrait spécifiquement favoriser l'infection tardive à SGB CC-17. Dans ce travail, le rôle de l'E2 et de la P4 aux concentrations retrouvées à la naissance (HormD0, E2 10-8M et P4 10-6M) et au-delà de 7 jours de vie (HormD7, E2 10-9 M et P4 10-7M) dans la physiopathologie des infections à SGB a été étudié dans des modèles cellulaires et murins d'infection utilisant deux souches de SGB représentatives, à la fois le clone hypervirulent CC-17 et un SGB non CC-17. Nous montrons que les concentrations HormD7 contribuent spécifiquement à la sévérité de la méningite due à SGB CC-17 dans un modèle murin d'infection par voie orale. Ce phénotype est lié à une augmentation du franchissement de la barrière digestive mis en évidence par un nombre plus important de bactéries dans les ganglions mésentériques et les plaques de Peyer. L'étude par microscopie optique d'anses intestinales ligaturées et de cultures cellulaires d'entérocytes-cellules M infectées par SGB CC-17 montre que SGB CC-17 peut franchir la barrière intestinale via les cellules M, que l'association aux cellules M est plus importante pour le clone CC-17, et qu'elle est favorisée par les conditions HormD7. Enfin, l'étude de mutants du clone CC-17 inactivés pour l'expression des protéines de surface spécifiques intervenant dans le franchissement des barrières physiologiques nous a permis de démontrer que l'association de SGB CC-17 aux cellules M est liée à la protéine Srr2 et que celle-ci contribue à la sévérité de la méningite en modèle murin dans les conditions HormD7 en favorisant la translocation intestinale de SGB CC-17 après infection par voie orale. L'identification du (des) récepteur(s) cellulaire(s) de la protéine Srr2 exprimé(s) par les cellules M, la régulation de son expression par les concentrations hormonales et la caractérisation des cascades de signalisation induites dans ces conditions constitueront la suite logique de ce travailStreptococcus agalactiae (Group B Streptococcus, GBS) is the leading cause of invasive bacterial neonatal infections for which two syndromes are defined, the early-onset disease (EOD, first week of life) and the late-onset disease (LOD, 7 to 89 days of life). EOD starts with pneumonia and results from the inhalation by the neonate of GBS-contaminated vaginal secretions or amniotic fluid. LOD manifests as a bacteremia for which the proposed portal of entry is the gastrointestinal tract and is characterized by a high rate of associated meningitis. A particular clone designated GBS CC-17 is responsible for nearly half of all EOD and for 70% of LOD and meningitis cases, while it is rarely responsible for infections in adults (15% of the cases). The hypervirulence of this CC-17 clone has been attributed to increased colonization and translocation capabilities of the gastrointestinal tract, as well as increased ability to cross the blood-brain barrier. However, these properties alone cannot explain its association with neonatal infections and host-related factors are likely involved. Throughout pregnancy, the fetus is exposed to increasing concentrations of maternal steroid hormones, particularly estradiol (E2) and progesterone (P4). Thus, newborn rates are 500 times higher than those of an adult male, then drop drastically in the first three days of life to stabilize for a few months at rates 5 to 50 times higher than in adults. These hormones regulate in a concentration-dependent manner the immune response, the permeability of cellular barriers, and the expression of adhesion molecules. Also, the massive hormonal impregnation of newborns could specifically promote GBS CC-17 late infections. In this work, the role of E2 and P4 at birth concentrations (HormD0, E2 10-8M and P4 10-6M) and beyond 7 days of life (HormD7, E2 10-9 M and P4 10-7M) in the pathophysiology of GBS infections was studied in cellular and mouse models of infection using two representative strains, a CC-17 hypervirulent GBS and a non-CC-17 GBS. We show that HormD7 concentrations specifically contribute to the severity of meningitis caused by GBS CC-17 in a mouse model of oral infection. This phenotype is linked to an increase in the crossing of the intestinal barrier highlighted by a greater number of bacteria in the mesenteric lymph nodes and Peyer's patches. Optical microscopy imaging of intestinal ligated loops and M cells-enterocytes co-cultures infected with GBS CC-17 shows that GBS CC-17 can cross the intestinal barrier through M cells, that the association with M cells is more important for the CC-17 clone compared to non-CC-17 GBS, and that it is favored in HormD7 condition. Finally, the study of isotype mutants of GBS CC-17 inactivated for the expression of specific surface proteins involved in the crossing of physiological barriers allowed us to demonstrate that the association of GBS CC-17 with M cells is linked to the Srr2 protein which contributes to the severity of meningitis under HormD7 condition by promoting the intestinal translocation of GBS CC-17 following mice oral infection. The identification of the cellular receptor(s) of the Srr2 protein expressed by M cells, their expression regulation by hormonal concentrations and the characterization of the signaling cascades induced in these conditions will constitute the logical continuation of this work
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Engelbrecht, Fredrika. "The antimicrobial susceptibility and gene-based resistance of Streptococcus Agalactiae (group B Streptococcus) in pregnant women in Windhoek (Khomas region), Namibia." Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/2238.
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Thesis (MTech (Biomedical Sciences))--Cape Peninsula University of Technology, 2015.BACKGROUND AND OBJECTIVES: Group B Streptococci (GBS) can asymptomatically colonise the vagina and rectum of women. Studies have shown that this bacterium is the leading cause of septicemia, meningitis and pneumonia in neonates. In Namibia no known studies have investigated GBS colonisation and the antibiotic resistance profile of GBS isolates in pregnant women. This study accessed the GBS colonisation rate amongst the pregnant women who attended the Windhoek Central Hospital Antenatal Clinic (Khomas region), in Namibia for a period of 13 months. Furthermore, using the VITEK 2 system, the GBS isolates were tested against the following antimicrobial substances; benzylpenicillin, ampicillin, clindamycin, erythromycin, tetracycline, vancomycin, cefotaxime, ceftriaxone, linezolid and trimethoprim/sulfamethoxazole. Penicillin G is the drug of choice in the majority of studies, and seems to be the most effective drug for intrapartum antibiotic prophylaxis (IAP). All the GBS isolates found in this study were also analysed for the presence of selected genes known to be associated with resistance to key antibiotics using specific primers within a polymerase chain reaction (PCR).
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Louçano, João [Verfasser]. "Synthesis and Optimization of Group B Streptococcus Capsular Polysaccharide Fragments Using the Glyconeer / João Louçano." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1215571879/34.
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Ipe, Deepak Samuel. "Molecular Mechanisms of Group B Streptococcus Urinary Tract Infection and Adaptability to Growth in Human Urine." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/366019.
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Bacteriuria, or the presence of bacteria in urine, is associated with both asymptomatic, as well as symptomatic urinary tract infection (UTI) and underpins much of the dynamic of microbial colonization of the urinary tract. The prevalence of bacteriuria in dissimilar patient groups such as healthy adults, institutionalized elderly, pregnant women, and immune-compromised patients varies widely. In addition, assessing the importance of ‘significant bacteriuria’ in infected individuals represents a diagnostic challenge, partly due to various causal microbes, and requires careful consideration of the distinct etiologies of bacteriuria in different populations and circumstances. Recent molecular discoveries have revealed how some bacterial traits can enable organisms to grow in human urine, which, as a fitness adaptation, is likely to influence the progression of bacteriuria in some individuals. This study was designed as a comprehensive analysis of asymptomatic bacteriuria (ABU) causal organisms in dissimilar populations, and an in-depth microbiological analysis of the mechanisms used by one such causal organism, Streptococcus agalactiae. This organism causes UTI including ABU; however, growth of S. agalactiae in human urine has not been reported. In the first part of this study, we evaluate the prevalence and etiology of bacteruria, and discuss recent advances in the molecular detection of bacteriuria from a diagnostic viewpoint.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Medical Science
Griffith Health
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Bergeron, Julie. "Inflammation gestationnelle induite par le streptocoque de groupe B inactivé : rôle de l'interleukine-1." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11101.
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Depuis les dernières décennies, plusieurs études épidémiologiques montrent des associations entre l’infection/inflammation durant la grossesse, les accouchements prématurés, les lésions cérébrales périnatales et les troubles neuro-développementaux ultérieurs tels que l’autisme. Le pathogène le plus fréquemment rencontré durant la grossesse est le streptocoque de groupe B (SGB). Le SGB colonise le tractus gastro-intestinal et/ou vaginal de 10 à 30% des femmes enceintes et provoque une combinaison d’infection et d’inflammation dont la cible la plus fréquente est le placenta (chorioamnionite). Nous avions précédemment montré, à l’aide d’un modèle animal pré-clinique (rat), que l’exposition systémique au SGB inactivé en fin de gestation induit une chorioamnionite, des lésions cérébrales ainsi que des traits comportementaux de type autistique dans la progéniture mâle.
Dans le cadre de ce travail, nous avons précisé la nature de la réaction inflammatoire sous-jacente à l’exposition maternelle au SGB inactivé en fin de gestation. Cette réaction inflammatoire est caractérisée par une surexpression d’IL-1β à la fois dans le plasma maternel, le placenta et le plasma foetal. Les placentas présentent une chorioamnionite sévère, principalement caractérisée par des infiltrations de cellules inflammatoires (majoritairement des cellules polymorphonucléaires neutrophiles (PMN), s’étendant jusqu’au versant foetal placentaire. De manière générale, les tissus associés aux foetus mâles présentent des niveaux d’inflammation supérieurs, autant par le profil d’expression des cytokines pro-inflammatoires (IL-1β, IL-6 et TNF-α) que par les infiltrations de PMN.
Puisque l’IL-1 est une cytokine pro-inflammatoire associée au travail préterme, aux lésions cérébrales ainsi qu’à l’autisme, nous avons tenté de valider son rôle dans la genèse des troubles neuro-développementaux SGB-induits dans notre modèle. Toutefois, le rôle de l’IL-1 n’a pu être élucidé.
Ces résultats supportent les évidences croissantes que le sexe foetal impacte la susceptibilité du foetus face aux agressions inflammatoires. Ces résultats ouvrent plusieurs nouvelles avenues de recherche, notamment sur l’identification de joueurs clés dans la réaction inflammatoire materno-foetale suivant l’exposition au SGB et ainsi développer de nouvelles mesures pour protéger le placenta et le cerveau du foetus en développement.Abstract : For the last decades, epidemiological studies have associated preterm birth, cerebral lesions and neurodevelopmental disorders to infection and/or inflammation during pregnancy. One of the most common pathogen encountered during gestation is Group B Streptococcus (GBS), which colonizes 10 to 30% of pregnant women’s gastro-intestinal and/or vaginal tracts. We have previously shown - with a preclinical rat model - that exposure to killed GBS at the end of gestation leads to placental and cerebral lesions. Moreover, only male offspring from mothers who experienced GBS-induced gestational inflammation displayed autistic-like behavior. In this work, we analyzed the inflammatory response to maternal inactivated GBS exposure at the end of gestation. This inflammatory response involves IL-1β, which is over expressed in maternal plasma, placenta and fetal plasma. Placentas displayed acute signs of histological chorioamnionitis, with polymorphonuclear cells (PMN) infiltrations even on the fetal side of placenta. Following GBS-induced inflammation, tissues associated to male fetuses generally showed increased inflammatory response as compared to females (IL-1β, IL-6 and TNF-α) and higher PMN placental infiltrations. Because IL-1β is associated to preterm birth, cerebral damage and autism, we wanted to validate the role of IL-1 in the onset of GBS-induced autism-like behavior in our animal model. However, at this stage, we have not been able to demonstrate this role. These results support the evidences that fetal sex matters for fetal susceptibility to inflammatory aggressions during pregnancy. These results pave the way toward the identification of key molecules in chorioamnionitis, brain damage and subsequent neurobehavioral disorders. This will help to find new strategies to protect the placenta and the fetal brain.
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Taylor, Karen Leigh. "A study of group B streptococcus in Brisbane : the epidemiology, detection by PCR assay and serovar prevalence." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16462/1/Karen_Taylor_Thesis.pdf.
Full textAbstract:
The neonate is still at risk of acquiring Group B Streptococcus (GBS) infection upon delivery even with the implementation of early onset GBS neonatal disease preventative protocols. GBS was reported as the most prevalent organism causing neonatal morbidity and mortality in the USA and Australia in the 1990s. GBS is also known to cause disease in children, women, the immunocompromised adult and the elderly, but it is the preterm neonates who are at greatest risk of GBS neonatal disease.
The aim of this study was to determine the prevalence of lower genital tract (LGT) colonisation with GBS in Brisbane women of child bearing age. We also aimed: (i) to compare the GBS LGT prevalence rate of Indigenous and non Indigenous women; (ii) to determine whether previously reported risk factors for LGT colonisation with GBS were also risk factors associated with GBS colonisation of women in this study; (iii) to further develop and optimise a rapid PCR assay that could detect maternal LGT GBS colonisation; and (iv) to serotype the GBS strains that were isolated from pregnant and non pregnant women who participated in this study.
This study recruited 374 women of childbearing age attending public medical providers and found an overall GBS prevalence of 98/374 (26.2%) for these Brisbane women, a rate higher than previously reported in Australia. When the GBS prevalence for pregnant women (25.6%) was compared to non pregnant women (27.2%) they were similar. We also compared the GBS LGT colonisation rate of women attending different medical providers. The GBS LGT prevalence rate for pregnant women attending the Mater was 36/118 (30.5%), whilst those women attending the Redlands Hospital antenatal clinic had a LGT GBS prevalence rate of only 7/53 (13.2%). By comparison, the LGT GBS prevalence rate for non pregnant women attending Biala Sexual Health clinic was 21/69 (30.4%) and 34/127 (26.8%) of women attending the Brisbane Family Planning Queensland were also GBS positive. The seven women recruited from Inala community centre tested negative for GBS LGT colonisation. The LGT GBS prevalence of Australian Aboriginal women was 5/22 (22.7%), a rate which was not significantly different from non-Aboriginal women 78/288 (27.1%).
Established early onset GBS neonatal disease preventative policies have been recently revised. The CDC now recommends that all pregnant women are screened for LGT GBS colonisation during late gestation, and that any GBS isolates be tested for resistance to antibiotics if the GBS positive women have an allergy to penicillin. Queensland's Department of Health recommend that Queensland medical agencies implement a non screening based preventative protocol, where clinicians monitor: women prior to labour for reported risk factors associated with maternal GBS colonisation: women in labour for 'obstetric risk factors'.
A number of risk factors have previously been reported in association with GBS LGT colonisation. However, in this current study we found that only one risk factor was significantly associated with current GBS: previous reported LGT GBS colonisation was significantly associated with maternal LGT GBS colonisation reported in this study. Women who previously tested positive for GBS were significantly more likely to be GBS positive in subsequent tests (OR 4.7; 95%CI, 1.8-12.5) compared to women with no previous history of GBS colonisation.
An assessment of adverse pregnancy outcomes, preterm deliveries, and GBS colonisation data was made. It was established that 30 women had previously given birth to one or more preterm neonates and of these 30 women, nine (30%) of them tested positive for GBS in this current study. Of the 71 women who had given birth to neonates and who had suffered an adverse pregnancy outcome 25.3% also tested positive for GBS in this current study. GBS was identified in up to 30% of all mothers who had delivered their neonate preterm, 27.4% of women who had previously suffered miscarriages and 16.7% of women who had previously had stillbirths.
In this study we found that Australian Aboriginal women also had a greater risk of delivering neonates who suffered from an adverse pregnancy outcome in comparison to all other women. Twenty one of the 22 Aboriginal women had previously been pregnant at least once, and nine (42.9%) of these women had at least one prior adverse pregnancy outcome while seven (33.3%) of these women had previously delivered at least one neonate preterm. Of the 21 Aboriginal women who had a previous pregnancy more than half the total number of Aboriginal women (11/21) had either delivered one or more neonates preterm or had suffered from one or more adverse pregnancy outcomes. When the incidence of adverse pregnancy outcomes was compared for Aboriginal and all other women the results were surprising. Overall, this study found 216 women including Aboriginal women had previously been pregnant and of these women 71 (32.8%) of them suffered an adverse pregnancy outcome. By comparison, only 62 of 195 (31.8%) non Aboriginal women but nine out of 21 (41.9%) Australian Aboriginal women suffered from a previous adverse pregnancy outcome.
The clinical LGT GBS isolates found in this study of Brisbane women were typed and all nine GBS serotypes plus non typeable GBS serotypes were detected. Seventy women tested GBS culture positive and vaginal and/or perianal samples obtained from these women were evaluated. GBS serotype III was the serotype most frequently isolated from this total population, from 47.4% of pregnant women and 51.7% of non pregnant women. From some women only a single GBS serotype was isolated: in these women we found that GBS serotype III (50%) was the predominant isolate, followed by GBS serotype Ia isolated from 16.7% women. In addition 4.2% of women were colonised with GBS serotypes; Ib, II and V, whilst GBS serotypes IV and VII were isolated from 2.1% women. Non typeable GBS strains confirmed by latex agglutination tests accounted for 11.9% of all strains isolated from these Brisbane women.
This study identified multiple serovars in 15 clinical samples and found that 22 (31.4%) women were colonised with mixed GBS serotypes in samples collected from both vaginal and perianal regions. In five women the combination of serotypes III/Ia were identified and in other women combinations of serotypes III/II, III/IV, III/V, III/VIII, Ia/IV and Ib/NT were also detected. In two instances three serotype combinations were detected in samples from one woman and these included serotypes III/Ib/II and III/Ia/Ib. Isolates were also typed for women who were colonised in both vaginal and perianal regions and it was found that only 10 participants had identical isolates in both regions. GBS serotype III was the predominant serotype detected in women tested in this study and this is the serotype that has previously been associated with invasive infections in neonates.
GBS neonatal disease is a world wide economic, health and social burden affecting different ethnic groups and is preventable. Currently no vaccine technology is available for the prevention of GBS neonatal disease and the most effective EOGND preventative protocol would be to test for maternal GBS colonisation during labour, or screen women for GBS at >36 weeks' gestation and administer intrapartum antibiotic prophylaxis (IAP) to all women who tested positive for GBS. In this current study we utilised a rapid bsp PCR assay to detect LGT GBS colonisation in women of child bearing age. The PCR assay identified 62.5% of all vaginal and perianal positive culture GBS samples. The specificity of the PCR assay was 89% while the positive and negative predictive values were 56.8% and 91.1% respectively. This PCR assay using the current parameters is not an effective GBS detection assay but could be further optimised in the near future. This PCR assay could be an effective test in the future with the development of an alternative DNA extraction method to InstaGene (BioRad). However, this PCR assay if used in conjunction with the current culture method is able to detect a further 8.9% of women colonised with asymptomatic GBS.
Brisbane women aged between 26 to 35 years who are pregnant and who are attending public health care agencies are at greatest risk of being colonised with GBS. No disparity was identified when ethnicity or social standing were assessed.
The overall results of this study demonstrate that the LGT GBS prevalence rate in Brisbane women is 26.2% but this rate was higher at 30.5% for women attending a Brisbane sexual health clinic and for pregnant women attending the Mater Mothers' antenatal clinic.
GBS serovar III has been identified as the dominant serovar in our population group and this strain has been reported as the major cause of GBS disease in neonates and infants aged to three months. Disparity (11.1%) was reported when the incidence of adverse pregnancy outcomes amongst Aboriginal women was compared to non Aboriginal women. From the outcomes of this study it has been suggested that Queensland adopt a screening based GBS preventative protocol. It has also been suggested that an Australian wide GBS prevention strategy may further reduce the incidence of neonatal disease.
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Taylor, Karen Leigh. "A study of group B streptococcus in Brisbane : the epidemiology, detection by PCR assay and serovar prevalence." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16462/.
Full textAbstract:
The neonate is still at risk of acquiring Group B Streptococcus (GBS) infection upon delivery even with the implementation of early onset GBS neonatal disease preventative protocols. GBS was reported as the most prevalent organism causing neonatal morbidity and mortality in the USA and Australia in the 1990s. GBS is also known to cause disease in children, women, the immunocompromised adult and the elderly, but it is the preterm neonates who are at greatest risk of GBS neonatal disease. The aim of this study was to determine the prevalence of lower genital tract (LGT) colonisation with GBS in Brisbane women of child bearing age. We also aimed: (i) to compare the GBS LGT prevalence rate of Indigenous and non Indigenous women; (ii) to determine whether previously reported risk factors for LGT colonisation with GBS were also risk factors associated with GBS colonisation of women in this study; (iii) to further develop and optimise a rapid PCR assay that could detect maternal LGT GBS colonisation; and (iv) to serotype the GBS strains that were isolated from pregnant and non pregnant women who participated in this study. This study recruited 374 women of childbearing age attending public medical providers and found an overall GBS prevalence of 98/374 (26.2%) for these Brisbane women, a rate higher than previously reported in Australia. When the GBS prevalence for pregnant women (25.6%) was compared to non pregnant women (27.2%) they were similar. We also compared the GBS LGT colonisation rate of women attending different medical providers. The GBS LGT prevalence rate for pregnant women attending the Mater was 36/118 (30.5%), whilst those women attending the Redlands Hospital antenatal clinic had a LGT GBS prevalence rate of only 7/53 (13.2%). By comparison, the LGT GBS prevalence rate for non pregnant women attending Biala Sexual Health clinic was 21/69 (30.4%) and 34/127 (26.8%) of women attending the Brisbane Family Planning Queensland were also GBS positive. The seven women recruited from Inala community centre tested negative for GBS LGT colonisation. The LGT GBS prevalence of Australian Aboriginal women was 5/22 (22.7%), a rate which was not significantly different from non-Aboriginal women 78/288 (27.1%). Established early onset GBS neonatal disease preventative policies have been recently revised. The CDC now recommends that all pregnant women are screened for LGT GBS colonisation during late gestation, and that any GBS isolates be tested for resistance to antibiotics if the GBS positive women have an allergy to penicillin. Queensland's Department of Health recommend that Queensland medical agencies implement a non screening based preventative protocol, where clinicians monitor: women prior to labour for reported risk factors associated with maternal GBS colonisation: women in labour for 'obstetric risk factors'. A number of risk factors have previously been reported in association with GBS LGT colonisation. However, in this current study we found that only one risk factor was significantly associated with current GBS: previous reported LGT GBS colonisation was significantly associated with maternal LGT GBS colonisation reported in this study. Women who previously tested positive for GBS were significantly more likely to be GBS positive in subsequent tests (OR 4.7; 95%CI, 1.8-12.5) compared to women with no previous history of GBS colonisation. An assessment of adverse pregnancy outcomes, preterm deliveries, and GBS colonisation data was made. It was established that 30 women had previously given birth to one or more preterm neonates and of these 30 women, nine (30%) of them tested positive for GBS in this current study. Of the 71 women who had given birth to neonates and who had suffered an adverse pregnancy outcome 25.3% also tested positive for GBS in this current study. GBS was identified in up to 30% of all mothers who had delivered their neonate preterm, 27.4% of women who had previously suffered miscarriages and 16.7% of women who had previously had stillbirths. In this study we found that Australian Aboriginal women also had a greater risk of delivering neonates who suffered from an adverse pregnancy outcome in comparison to all other women. Twenty one of the 22 Aboriginal women had previously been pregnant at least once, and nine (42.9%) of these women had at least one prior adverse pregnancy outcome while seven (33.3%) of these women had previously delivered at least one neonate preterm. Of the 21 Aboriginal women who had a previous pregnancy more than half the total number of Aboriginal women (11/21) had either delivered one or more neonates preterm or had suffered from one or more adverse pregnancy outcomes. When the incidence of adverse pregnancy outcomes was compared for Aboriginal and all other women the results were surprising. Overall, this study found 216 women including Aboriginal women had previously been pregnant and of these women 71 (32.8%) of them suffered an adverse pregnancy outcome. By comparison, only 62 of 195 (31.8%) non Aboriginal women but nine out of 21 (41.9%) Australian Aboriginal women suffered from a previous adverse pregnancy outcome. The clinical LGT GBS isolates found in this study of Brisbane women were typed and all nine GBS serotypes plus non typeable GBS serotypes were detected. Seventy women tested GBS culture positive and vaginal and/or perianal samples obtained from these women were evaluated. GBS serotype III was the serotype most frequently isolated from this total population, from 47.4% of pregnant women and 51.7% of non pregnant women. From some women only a single GBS serotype was isolated: in these women we found that GBS serotype III (50%) was the predominant isolate, followed by GBS serotype Ia isolated from 16.7% women. In addition 4.2% of women were colonised with GBS serotypes; Ib, II and V, whilst GBS serotypes IV and VII were isolated from 2.1% women. Non typeable GBS strains confirmed by latex agglutination tests accounted for 11.9% of all strains isolated from these Brisbane women. This study identified multiple serovars in 15 clinical samples and found that 22 (31.4%) women were colonised with mixed GBS serotypes in samples collected from both vaginal and perianal regions. In five women the combination of serotypes III/Ia were identified and in other women combinations of serotypes III/II, III/IV, III/V, III/VIII, Ia/IV and Ib/NT were also detected. In two instances three serotype combinations were detected in samples from one woman and these included serotypes III/Ib/II and III/Ia/Ib. Isolates were also typed for women who were colonised in both vaginal and perianal regions and it was found that only 10 participants had identical isolates in both regions. GBS serotype III was the predominant serotype detected in women tested in this study and this is the serotype that has previously been associated with invasive infections in neonates. GBS neonatal disease is a world wide economic, health and social burden affecting different ethnic groups and is preventable. Currently no vaccine technology is available for the prevention of GBS neonatal disease and the most effective EOGND preventative protocol would be to test for maternal GBS colonisation during labour, or screen women for GBS at >36 weeks' gestation and administer intrapartum antibiotic prophylaxis (IAP) to all women who tested positive for GBS. In this current study we utilised a rapid bsp PCR assay to detect LGT GBS colonisation in women of child bearing age. The PCR assay identified 62.5% of all vaginal and perianal positive culture GBS samples. The specificity of the PCR assay was 89% while the positive and negative predictive values were 56.8% and 91.1% respectively. This PCR assay using the current parameters is not an effective GBS detection assay but could be further optimised in the near future. This PCR assay could be an effective test in the future with the development of an alternative DNA extraction method to InstaGene (BioRad). However, this PCR assay if used in conjunction with the current culture method is able to detect a further 8.9% of women colonised with asymptomatic GBS. Brisbane women aged between 26 to 35 years who are pregnant and who are attending public health care agencies are at greatest risk of being colonised with GBS. No disparity was identified when ethnicity or social standing were assessed. The overall results of this study demonstrate that the LGT GBS prevalence rate in Brisbane women is 26.2% but this rate was higher at 30.5% for women attending a Brisbane sexual health clinic and for pregnant women attending the Mater Mothers' antenatal clinic. GBS serovar III has been identified as the dominant serovar in our population group and this strain has been reported as the major cause of GBS disease in neonates and infants aged to three months. Disparity (11.1%) was reported when the incidence of adverse pregnancy outcomes amongst Aboriginal women was compared to non Aboriginal women. From the outcomes of this study it has been suggested that Queensland adopt a screening based GBS preventative protocol. It has also been suggested that an Australian wide GBS prevention strategy may further reduce the incidence of neonatal disease.
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Pangerl, Sabine. "The adherence to group b streptococcus screening guidelines amongst pregnant women in Western Australia – A quantitative descriptive analysis." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2448.
Full textAbstract:
Colonisation with Group B Streptococci (GBS) is a major risk factor for neonatal infection acquired via vertical transmission during pregnancy, labour, or birth, potentially resulting in significant morbidity and mortality. Universal screening at 35 – 37 weeks gestation for maternal GBS colonisation and the use of intrapartum antibiotic prophylaxis has resulted in substantial reductions in the burden of neonatal Early-Onset GBS Disease (EOGBSD). Women in Western Australia (WA) are offered GBS screening in pregnancy and intrapartum antibiotic prophylaxis. Anecdotal evidence suggests variations in viewpoints and thus low adherence to relevant clinical guidelines amongst midwives and pregnant women in the midwifery led model of care. To date, no research has been undertaken to provide empirical evidence for these anecdotal reports, suggesting the need for research.
This study has aimed to investigate the adherence to recommended GBS screening guidelines across five maternity hospitals in metropolitan and regional WA. Three objectives guided this research conducted within two different cohorts (midwifery and non-midwifery led) plus subgroups including Midwifery Group Practice (MGP), Community Midwifery Program (CMP) and Private Midwives (PM): 1) determination of GBS colonisation rates; 2) the examination of adherence to antenatal GBS screening; and 3) examination of adherence to the intrapartum antibiotic prophylaxis protocol.
This retrospective WA study has employed a quantitative research design using administrative health data that included 22,417 pregnant women who gave birth between 2015 – 2019. Descriptive statistics were applied using secondary data analysis to describe the characteristics and patterns of GBS screening guideline adherence. The results were compared between all involved study cohorts.
The study revealed similar GBS colonisation rates amongst pregnant women in all included study groups. A lower adherence to the GBS screening guidelines was found in the midwifery led model of care when compared to the non-midwifery led model of care. Over the five-year period, screening rates trended down in the midwifery led population whilst the numbers remained stable in the non-midwifery led cohort. When the MGP groups were compared across the five hospitals, vast variations were discovered. Further, when rates of adherence were investigated in relation to intrapartum antibiotic prophylaxis, discrepant findings emerged between the study groups.
This study not only fills an important gap in the existing literature, it also seeks to assist guidance and improvement of clinical protocols in relation to GBS screening to reduce the risk of neonatal infection. Recommendations include educational interventions and the need for further research.
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Desai, Devika J. "Characterisation of Biofilm-Forming Ability and Haemolytic Activity of Clinical Group B Streptococcus (GBS) Isolates From the Urinary Tract." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/398419.
Full textAbstract:
Urinary tract infections (UTIs) are among the most common infections caused by both Gram-negative and Gram-positive bacteria, acquired in the community and hospitals. There are three main groups of UTIs: (i) lower UTIs that affect the urethra or the bladder, (ii) upper UTIs that affect the kidneys, or (iii) asymptomatic bacteriuria (ABU).
Group B Streptococcus (GBS) is a Gram-positive bacteria known to cause a variety of infections in neonates, pregnant women, the elderly or immunocompromised individuals. GBS has been estimated to cause 1-2% of all single organism UTIs. GBS has been shown to form biofilms, on abiotic and biotic surfaces, protecting it from killing by antibiotics or host immune cells and promotes host colonisation. Various factors have been shown to affect the biofilm forming ability of GBS. Here we determined that LB supplemented with glucose was the optimal media for biofilm formation by a strong biofilm forming strain. We then investigated the biofilm forming phenotype of 292 clinical GBS isolates that presented with asymptomatic, acute, or recurrent infection. We found that there was no significant difference in the biofilm forming ability across the clinical presentations. We also showed a significant reduction in the biofilm forming ability of a strong biofilm forming strain and its isogenic maeK and maeE mutants in LB supplemented with 1% glucose. A multiplex PCR screen for genes encoding bsaB, pil1, pil2a, and pil2b found that there was no significant difference in the number of strains that had the right sized fragments for all four genes across the three clinical presentations. We also found that there was a significant difference in the proportion of strains that had the right sized fragments for the pil genes across the three different levels of biofilm activity under shaking conditions. High biofilm forming strains had the lowest proportion of strains that possessed all four genes, compared to low and medium biofilm formers. Lastly, we assessed the haemolytic activity of the strains by growing them on tryptic soy agar plates supplemented with 5% horse blood and found that asymptomatic strains had a significantly higher number of strains with high haemolytic activity compared to acute and recurrent strains.Thesis (Masters)
Master of Medical Research (MMedRes)
School of Medical Science
Griffith Health
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Dias, João Félix. "Colonização por estreptococo do grupo B em gestantes em Cuiabá." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/5/5141/tde-29102014-154314/.
Full textAbstract:
Objetivos: Determinar a taxa de prevalência de colonização materna por Estreptococo do grupo B na população de gestantes com idade gestacional de 35 semanas ou mais frequentadoras do pré-natal em dois hospitais (Hospital Universitário Júlio Muller - HUJM e Hospital Beneficente Santa Helena) na cidade de Cuiabá, Mato Grosso. Materiais e Métodos: Entre outubro de 2011 e 2013 foram avaliadas 258 gestantes no HUJM e do Hospital Santa Helena. Após concordarem e assinarem o TCLE, as gestantes de 35 semanas ou mais que não tinham sido submetidas ao exame ginecológico e não estavam em uso de antibióticos e atendiam aos critérios de inclusão, foram submetidas a coleta de swab vaginal e retal conforme protocolo estabelecido. Acondicionado em meio de transporte Stuart e no laboratório cultivado em caldo Granada bifásico IGBL. Após 24 horas, amostras com coloração laranja ou avermelhada foram consideradas positivas, caso contrário, nova leitura com 48 horas de cultivo. Os dados foram submetidos a análise estatística utilizando o EPI-Info da OMS. Resultados: Das 258 amostras 13,95% foram positivas para o EGB com IC (95%) de 9.70% a 18.21%. A avaliação estratificada pela idade gestacional predominou nas gestantes de 36 semanas com 35% de positividade, 10.87% para 37 semanas. E 5.88% para 35 semanas. No trabalho de parto prematuro 33.33% e na amniorrexe prematura 28,57% dos casos eram positivos para o EGB. Os demais parâmetros analisados não mostraram significância estatística. Conclusões: A taxa de prevalência da colonização pelo EGB de uma forma global foi estimada em 13.95%, sendo mais elevada na idade gestacional de 36 semanas com taxa de 35%. Este trabalho deve mudar as políticas públicas de saúde na cidade de CuiabáPurpose: To determine the prevalence rate of maternal colonization by Group B Streptococcus in the population of pregnant women in the gestational age of 35 or more weeks, attending prenatal care in two hospitals (HUJM - Hospital Universitário Júlio Muller and Hospital Santa Helena), in the city of Cuiabá, Mato Grosso. Materials and methods: Between October 2011 and October 2013, 258 pregnant women were assessed in HUJM and Hospital Santa Helena. After agreeing and signing the FCCT (Free and clarified Consent Term), those pregnant women of 35 weeks or more, who had not undergone gynecological examination, who were not on antibiotics and who also met the inclusion criteria, were subjected to vaginal and rectal swab collection, according to the established protocol. Stowed in Stuart transport medium and cultivated in IGBL biphasic Granada Broth in the laboratory. After 24 hours, samples with orange or reddish colors were considered positive, otherwise, new evaluation with a 48-hour culture was done. Data were submitted to statistical analysis, using OMS\' EPI-Info. The results: From the 258 given samples, 13.21% were positive for EGB, CI (95%) from 9.70% to 18.21%. Evaluation stratified by gestational age was predominant in pregnant women of 36 weeks with 35% positivity rate, 10.87% of pregnant women of 37 weeks and 5.88% of women of 35 weeks. During preterm labor 33.33% and in premature rupture of membranes, 28.57% cases were positive for GBS. Other analyzed parameters showed no significant statistically. Conclusion: The overall prevalence rate of GBS colonization was estimated at 13.95%, being higher in the gestational age of 36 weeks, with a rate of 35%. The present work should change public health policies in the city of Cuiabá
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Bouhafs, Rabea K. L. "Direct and phagocyte-mediated lipid peroxidation of lung surfactant by group B streptococci and other bacteria : protective effects of antioxidants /." Stockholm, 2002.
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Beauruelle, Clémence. "Locus CRISPR de Streptococcus agalactiae : marqueur génétique de la phylogénie de l'espèce et de l'évolution récente des isolats." Electronic Thesis or Diss., Tours, 2019. http://www.theses.fr/2019TOUR3806.
Full textAbstract:
Nous avons étudié l’intérêt du locus CRISPR1 (associé au système CRISPR-Cas de type II-A), comme marqueur épidémiologique pour le typage et l’analyse phylogénétique des souches de Streptococcus agalactiae, le streptocoque du groupe B (SGB). Par ce travail de thèse, nous avons pu mettre en évidence i) l’activité du système CRISPR-Cas in vivo ainsi que sa faible vitesse d’évolution ii) une conservation des marqueurs ancestraux, permettant d’obtenir des informations sur les lignées phylogénétiques (congruence entre le typage CRISPR et le MLST), iii) un polymorphisme du locus CRISPR1 (notamment des spacers d’acquisition récente), offrant une méthode de typage très discriminante (séparation des isolats au sein d’un même ST définit par MLST). L’analyse de ces spacers nous donne également des informations sur l’évolution récente des isolats, notamment de leurs contacts avec les EGMs. Nous avons montré l’intérêt de cet outil pour le suivi de souches de portage ou l’étude d’une population. Ainsi, à l’issu de ce travail de thèse nous proposons le typage CRISPR comme méthode de référence pour le typage et l’analyse phylogénétique des souches de SGBWe studied the relevance of the CRISPR1 array (associated to a CRISPR-Cas II-A type) as an epidemiological marker for genotyping and phylogenetic analyses of Streptococcus agalactiae (or Group B Streptococcus (GBS)) isolates. We demonstrate that i) spacer acquisition events occurred in vivo which strongly suggest that the CRISPR1-Cas system is functionally active for adaptation ii) ancestral markers (TDR and ancestral spacers) are highly conserved and reflect the phylogenetic structure of the GBS population (in congruence with MLST) iii) CRISPR1 array shared a high degree of polymorphism (especially for leader end spacers) offering a highly discriminatory typing method (allow to separate isolates within a same ST defined by MLST). Leader end analysis also provides specific evidence on isolates recent evolution, especially encounters with MGEs. CRISPR1 array appears as a useful genetic feature to follow vaginal carriage of GBS in women and for evaluate the diversity of GBS vaginal carriage population. On the basis of these data, we assume that this method could pretend to be a reference method for phylogenetic GBS typing
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Bergseng, Håkon. "Aspects of Group B streptococcus(GBS) disease in the newborn : Epidemiology, characterisation of invasive strains and evaluation of intrapartum screening." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for laboratoriemedisin, barne- og kvinnesykdommer, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5527.
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