Articles de revues : « Strains emergence »

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Coburn, Brian J., Chris Cosner et Shigui Ruan. « Emergence and dynamics of influenza super-strains ». BMC Public Health 11, Suppl 1 (2011) : S6. http://dx.doi.org/10.1186/1471-2458-11-s1-s6.

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Voineagu, Lavinia, Victoria Braga, Mihaela Botnarciuc, Adina Barbu et Mirela Tataru. « Emergence of Staphylococcus hominis Strains in General Infections ». ARS Medica Tomitana 18, n^o 2 (1 décembre 2012) : 80–82. http://dx.doi.org/10.2478/v10307-012-0016-8.

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Abstract A retrospective analysis of microbiology data from general infections was performed. From 105 isolates strains of Staphylococcus spp. 36 (34,28%) were Staphylococcus epidermidis, 33 (31,42%) Staphylococcus aureus, 21 (20%) Staphylococcus haemolyticus, and 15 (14,28%) were Staphylococcus hominis. Results: S. hominis isolates were predominantly resistant to betalactamins (93,33 %) and even Imidazole (60 %). 53,33 % of strains were resistent to aminosides and 33,33 % to Ciprofloxacin. All strains (100%) were sensitive to Vancomycin, but also all were susceptibile to Quinupristin-Dalfopristin. A high percentage of S. hominis were sensitive to Moxifloxacin, Linezolid (93,33 %), and to teicoplanin (86,67%). Discussion: S. hominis is a member of skin normal flora, but all strains of S. hominis were isolated from generalized infection with a high rate of mortality.

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DALSGAARD, A., O. SERICHANTALERGS, A. FORSLUND, C. PITARANGSI et P. ECHEVERRIA. « Phenotypic and molecular characterization of Vibrio cholerae O1 isolated in Samutsakorn, Thailand before, during and after the emergence of V. cholerae O139 ». Epidemiology and Infection 121, n^o 2 (octobre 1998) : 259–68. http://dx.doi.org/10.1017/s0950268898001125.

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Seventy clinical strains of Vibrio cholerae O1 isolated from 1982–96 in Samutsakorn, a port city 30 km southwest of Bangkok where cholera occurs at low levels with regular seasonality, were characterized to investigate if there were any differences among the O1 strains isolated before, during and after the O139 epidemic. Pulsed-field gel electrophoresis (PFGE) typing, ribotyping and southern blot hybridization with a cholera toxin probe (CT genotyping) demonstrated several genotypes among O1 strains isolated before the emergence of V. cholerae O139. However, O1 strains isolated during and after the advent of O139 showed identical ribotypes which were distinctly different from the types identified in strains isolated before the emergence of O139. Ribotypes identified in strains during and after the advent of O139 were also demonstrated by O1 strains isolated immediately before the emergence of O139. Considering the seasonality of cholera in Samutsakorn, the identical ribotype and CT genotype and the closely related PFGE types shown by all O1 strains isolated during and after the appearance of O139 is remarkable and suggest that the V. cholerae O1 strain may reemerge from an environmental source. A subgroup of V. cholerae O1 strains isolated before the emergence of the O139 epidemic had a ribotype identical to a type demonstrated by O139 strains isolated in Thailand. Our results support similar findings in Bangladesh and India that a distinct O1 strain appeared during the O139 epidemic. However, compared with the apparent identical strain which replaced O139 in Bangladesh and India, the emerged O1 strain in Samutsakorn showed a different ribotype and CT genotype.

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Ohtsuka, Masayuki, Ken Kikuchi, Kenichiro Shimizu, Namiko Takahashi, Yuka Ono, Takashi Sasaki et Keiichi Hiramatsu. « Emergence of Quinolone-Resistant Bordetella pertussis in Japan ». Antimicrobial Agents and Chemotherapy 53, n^o 7 (4 mai 2009) : 3147–49. http://dx.doi.org/10.1128/aac.00023-09.

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ABSTRACT Six Bordetella pertussis strains isolated from children in Japan from 2004 to 2006 showed high-level resistance to nalidixic acid (NAL; MIC, >256 μg/ml) and decreased susceptibilities to fluoroquinolones. All of the NAL-resistant strains had the same D87G mutation in gyrA.

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Steele, A. D., et B. Ivanoff. « Rotavirus strains circulating in Africa during 1996–1999 : emergence of G9 strains and P[6] strains ». Vaccine 21, n^o 5-6 (janvier 2003) : 361–67. http://dx.doi.org/10.1016/s0264-410x(02)00616-3.

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Salerno, Francesco, et Massimo Cazzaniga. « Therapeutic strategies and emergence of multiresistant bacterial strains ». Internal and Emergency Medicine 5, S1 (24 septembre 2010) : 45–51. http://dx.doi.org/10.1007/s11739-010-0447-9.

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Eyngor, Marina, Yoram Tekoah, Roni Shapira, Avshalom Hurvitz, Amir Zlotkin, Avishay Lublin et Avi Eldar. « Emergence of Novel Streptococcus iniae Exopolysaccharide-Producing Strains following Vaccination with Nonproducing Strains ». Applied and Environmental Microbiology 74, n^o 22 (19 septembre 2008) : 6892–97. http://dx.doi.org/10.1128/aem.00853-08.

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ABSTRACT Streptococcus iniae is a major pathogen of fish, producing fatal disease among fish species living in very diverse environments. Recently, reoccurrences of disease outbreaks were recorded in rainbow trout (Oncorhynchus mykiss, Walbaum) farms where the entire fish population was routinely vaccinated. New strains are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide that is released into the medium. Present findings indicate that the extracellular polysaccharide is a major antigenic factor, suggesting an evolutionary selection of strains capable of extracellular polysaccharide production.

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Lipnitskiy, A. V., I. A. Barkova, V. A. Antonov, A. M. Barkov et A. V. Novozhenina. « TO THE QUESTION OF THE EVOLUTION OF BACILLUS ANTHRACIS MICROBE ». Epidemiology and Infectious Diseases 18, n^o 5 (15 octobre 2013) : 49–55. http://dx.doi.org/10.17816/eid40794.

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The objective of the review - the analysis of results of researches on the characteristics of strains of bacilli from the B.cereus sensu lato group, causing anthrax-like diseases of the people and some animal species. The facts testify that along with the evolution of Bacillus anthracis microbe which has led to acquisition of major factors of virulence - plasmids рХО1 and рХО2, emergence of strains of bacilli with plasmids of virulence similar to B. anthracis, but retaining B.cereus sensu strico properties is possible. The reasons and conditions of emergence of such strains aren't established yet.

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Vandenbussche, Frank, Elisabeth Mathijs, Wannes Philips, Meruyert Saduakassova, Ilse De Leeuw, Akhmetzhan Sultanov, Andy Haegeman et Kris De Clercq. « Recombinant LSDV Strains in Asia : Vaccine Spillover or Natural Emergence ? » Viruses 14, n^o 7 (29 juin 2022) : 1429. http://dx.doi.org/10.3390/v14071429.

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From 2017 to 2019, several vaccine-like recombinant strains of lumpy skin disease virus (LSDV) were discovered in Kazakhstan and neighbouring regions of Russia and China. Shortly before their emergence, the authorities in Kazakhstan launched a mass vaccination campaign with the Neethling-based Lumpivax vaccine. Since none of the other countries in the affected region had used a homologous LSDV vaccine, it was soon suspected that the Lumpivax vaccine was the cause of these unusual LSDV strains. In this study, we performed a genome-wide molecular analysis to investigate the composition of two Lumpivax vaccine batches and to establish a possible link between the vaccine and the recent outbreaks. Although labelled as a pure Neethling-based LSDV vaccine, the Lumpivax vaccine appears to be a complex mixture of multiple CaPVs. Using an iterative enrichment/assembly strategy, we obtained the complete genomes of a Neethling-like LSDV vaccine strain, a KSGP-like LSDV vaccine strain and a Sudan-like GTPV strain. The same analysis also revealed the presence of several recombinant LSDV strains that were (almost) identical to the recently described vaccine-like LSDV strains. Based on their InDel/SNP signatures, the vaccine-like recombinant strains can be divided into four groups. Each group has a distinct breakpoint pattern resulting from multiple recombination events, with the number of genetic exchanges ranging from 126 to 146. The enormous divergence of the recombinant strains suggests that they arose during seed production. The recent emergence of vaccine-like LSDV strains in large parts of Asia is, therefore, most likely the result of a spillover from animals vaccinated with the Lumpivax vaccine.

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Doan, Yen Hai, Francis Ekow Dennis, Nobuhiro Takemae, Kei Haga, Hiroyuki Shimizu, Michael Gyasi Appiah, Belinda Larteley Lartey et al. « Emergence of Intergenogroup Reassortant G9P[4] Strains Following Rotavirus Vaccine Introduction in Ghana ». Viruses 15, n^o 12 (18 décembre 2023) : 2453. http://dx.doi.org/10.3390/v15122453.

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Rotavirus (RVA) is a leading cause of childhood gastroenteritis. RVA vaccines have reduced the global disease burden; however, the emergence of intergenogroup reassortant strains is a growing concern. During surveillance in Ghana, we observed the emergence of G9P[4] RVA strains in the fourth year after RVA vaccine introduction. To investigate whether Ghanaian G9P[4] strains also exhibited the DS-1-like backbone, as seen in reassortant G1/G3/G8/G9 strains found in other countries in recent years, this study determined the whole genome sequences of fifteen G9P[4] and two G2P[4] RVA strains detected during 2015–2016. The results reveal that the Ghanaian G9P[4] strains exhibited a double-reassortant genotype, with G9-VP7 and E6-NSP4 genes on a DS-1-like backbone (G9-P[4]-I2-R2-C2-M2-A2-N2-T2-E6-H2). Although they shared a common ancestor with G9P[4] DS-1-like strains from other countries, further intra-reassortment events were observed among the original G9P[4] and co-circulating strains in Ghana. In the post-vaccine era, there were significant changes in the distribution of RVA genotype constellations, with unique strains emerging, indicating an impact beyond natural cyclical fluctuations. However, reassortant strains may exhibit instability and have a limited duration of appearance. Current vaccines have shown efficacy against DS-1-like strains; however, ongoing surveillance in fully vaccinated children is crucial for addressing concerns about long-term effectiveness.

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Lukashev, A. N., V. A. Lashkevich, G. A. Koroleva, J. Ilonen et A. E. Hinkkanen. « Recombination in uveitis-causing enterovirus strains ». Journal of General Virology 85, n^o 2 (1 février 2004) : 463–70. http://dx.doi.org/10.1099/vir.0.19469-0.

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The complete nucleotide sequences of three human echovirus (EV) 11 strains and one EV19 strain, all of which caused outbreaks of enterovirus uveitis (EU), a new infant disease first identified in 1980 in Siberia, were determined. One EV11 strain which caused an outbreak of sepsis-like disease in Hungary was also sequenced. All four EV11 strains were mosaic recombinants of the prototype EV11 strain Gregory, with their non-structural coding regions and 5′ NTRs being more similar to other prototype enteroviruses (EV1, EV9). However, this finding is probably a feature of all circulating enterovirus strains and may not be related to their altered virulence. A full genome sequence comparison of the three subtypes of EU-causing strains excludes the role of recent recombination in their emergence, and points to their independent emergence.

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Cui, Mingquan, Jiyun Li, Tariq Ali, Khisrao Kalim, Hejia Wang, Li Song, Zekun Li et al. « Emergence of livestock-associated MRSA ST398 from bulk tank milk, China ». Journal of Antimicrobial Chemotherapy 75, n^o 12 (14 août 2020) : 3471–74. http://dx.doi.org/10.1093/jac/dkaa367.

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Abstract Objectives To detect livestock-associated MRSA (LA-MRSA) ST398 from bulk tank milk in China and to determine the phenotypic and genomic characteristics of the strains. Methods LA-MRSA ST398 strains were isolated from bulk tank milk samples in Shanghai and their susceptibilities to antimicrobials were determined using the broth dilution method. Genomic characterization of MRSA ST398 strains was performed by WGS and their evolutionary relationships were assessed by phylogenetic analysis. Results Two LA-MRSA ST398 isolates were recovered from bulk tank milk samples in two geographically distant farms in China. Whole-genome analysis strongly suggested that the LA-MRSA ST398 strains were closely related to the highly virulent hospital-associated MRSA (HA-MRSA) ST398 strains in China. Conclusions The presence of LA-MRSA ST398 in bulk tank milk might be a serious threat to public health, highlighting the need for active surveillance of LA-MRSA in healthy cattle in China.

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Tschudin-Sutter, Sarah, Reno Frei, Günter Kampf, Michael Tamm, Eric Pflimlin, Manuel Battegay et Andreas Franz Widmer. « Emergence of Glutaraldehyde-Resistant Pseudomonas aeruginosa ». Infection Control & ; Hospital Epidemiology 32, n^o 12 (décembre 2011) : 1173–78. http://dx.doi.org/10.1086/662624.

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Objective.In November 2009, routine sampling of endoscopes performed to monitor the effectiveness of the endoscope-cleaning procedure at our hospital detected Pseudomonas aeruginosa. Herein we report the results of the subsequent investigation.Design and Methods.The investigation included environmental cultures for source investigation, molecular analysis by pulsed-field gel electrophoresis (PFGE) to reveal the identity of the strains, and determination of the bactericidal activity of the glutaraldehyde-based disinfectant used for automated endoscope reprocessing. In addition, patient outcome was analyzed by medical chart review, and incidence rates of clinical samples with P. aeruginosa were compared.Setting.The University Hospital of Basel is an 855-bed tertiary care center in Basel, Switzerland. Approximately 1,700 flexible bronchoscopic, 2,500 gastroscopic, 1,400 colonoscopic, 140 endoscopic retrograde cholangiopancreatographic, and 140 endosonographic procedures are performed annually.Results.P. aeruginosa was detected in samples obtained from endoscopes in November 2009 for the first time since the initiation of surveillance in 2006. It was found in the rinsing water and in the drain of 1 of the 2 automated endoscope reprocessors. PFGE revealed 2 distinct P. aeruginosa strains, one in each reprocessor. The glutaraldehyde-based disinfectant showed no activity against the 2 pseudo-outbreak strains when used in the recommended concentration under standard conditions. After medical chart review, 6 patients with lower respiratory tract and bloodstream infections were identified as having a possible epidemiological link to the pseudo-outbreak strain.Conclusions.This is the first description of a pseudo-outbreak caused by P. aeruginosa with reduced susceptibility to an aldehyde-based disinfectant routinely used in the automated processing of endoscopes.

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Bálint, Ádám, István Kiss, Krisztián Bányai, Imre Biksi, Katalin Szentpáli-Gavallér, Tibor Magyar, István Jankovics et al. « Emergence and characterisation of pandemic H1N1 influenza viruses in Hungarian swine herds ». Acta Veterinaria Hungarica 61, n^o 1 (1 mars 2013) : 125–34. http://dx.doi.org/10.1556/avet.2012.059.

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In 2010, two novel porcine H1N1 influenza viruses were isolated from pigs with influenza-like illness in Hungarian swine herds. Sequence and phylogenetic analysis of these strains revealed that they shared molecular features with the pandemic H1N1 influenza virus strains, which emerged globally during 2009. The PB2, HA and NA genes contained unique amino acid changes compared to the available new H1N1 influenza virus sequences of pig origin. Furthermore, the investigated strains could be separated with respect to parallel amino acid substitutions affecting the polymerase genes (PB2, PB1 and PA) and the nucleoprotein (NP) gene, supporting the proposed complementarities between these proteins, all required for the viral fitness. Molecular characterisation of two Hungarian human pandemic H1N1 isolates was also performed, so that we could compare contemporaneous strains of different host species origins. Shared molecular motifs in various genes of animal and human influenza strains suggested that the Hungarian porcine strains could have originated from humans through direct interspecies transmission. This study is among the few that support the natural human-to-pig transmission of the pandemic H1N1 influenza virus.

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RHEE, CHAE HONG, et GUN-JO WOO. « Emergence and Characterization of Foodborne Methicillin-Resistant Staphylococcus aureus in Korea ». Journal of Food Protection 73, n^o 12 (1 décembre 2010) : 2285–90. http://dx.doi.org/10.4315/0362-028x-73.12.2285.

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A total of 165 Staphylococcus aureus strains, isolated from different food samples between 2003 and 2006, were tested for antimicrobial susceptibility. The mecA-positive methicillin-resistant S. aureus (MRSA) strains were further characterized by testing for various virulence genes and by molecular typing with multilocus sequence typing and pulsed-field gel electrophoresis. Of the 165 S. aureus isolates, 150 strains (90.9%) were resistant to at least one antibiotic while no strain was resistant to vancomycin. Four strains were resistant to both oxacillin and cefoxitin and were mecA positive. The mecA-positive MRSA strains were isolated from raw meat and fish samples (two beef samples and two fish samples) and were resistant to β-lactam antibiotics. Based on multilocus sequence typing analysis, the isolates were assigned to sequence type 1 (ST1), ST72, and an undetermined ST (ST72 slv). All four MRSA isolates were shown to be enterotoxigenic. The ST1 MRSA isolate harbored the sea-seh gene combination and the ST72 and ST72 slv MRSA strains harbored the seg-sei and the sea-seg-sei gene combinations, respectively. However, none of the MRSA isolates had the genes for Panton-Valentine leukocidin, toxic shock syndrome toxin 1, and exfoliative toxins. The pulsed-field gel electrophoresis patterns of the ST72 isolates in our study were highly similar, even though they were isolated from food samples in different years and from different regions of Korea.

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Kucharski, Adam, et Julia R. Gog. « Influenza emergence in the face of evolutionary constraints ». Proceedings of the Royal Society B : Biological Sciences 279, n^o 1729 (20 juillet 2011) : 645–52. http://dx.doi.org/10.1098/rspb.2011.1168.

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Different influenza subtypes can evolve at very different rates, but the causes are not well understood. In this paper, we explore whether differences in transmissibility between subtypes can play a role if there are fitness constraints on antigenic evolution. We investigate the problem using a mathematical model that separates the interaction of strains through cross-immunity from the process of emergence for new antigenic variants. Evolutionary constraints are also included with antigenic mutation incurring a fitness cost. We show that the transmissibility of a strain can become disproportionately important in dictating the rate of antigenic drift: strains that spread only slightly more easily can have a much higher rate of emergence. Further, we see that the effect continues when vaccination is considered; a small increase in the rate of transmission can make it much harder to control the frequency at which new strains emerge. Our results not only highlight the importance of considering both transmission and fitness constraints when modelling influenza evolution, but may also help in understanding the differences between the emergence of H1N1 and H3N2 subtypes.

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Mondal, Shaonpius, Yu-Hsuan Lin, Juliet E. Carroll, Erik J. Wenninger, Nilsa A. Bosque-Pérez, Jonathan L. Whitworth, Pamela Hutchinson, Sanford Eigenbrode et Stewart M. Gray. « Potato virus Y Transmission Efficiency from Potato Infected with Single or Multiple Virus Strains ». Phytopathology® 107, n^o 4 (avril 2017) : 491–98. http://dx.doi.org/10.1094/phyto-09-16-0322-r.

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There has been a recent shift in the prevalence of Potato virus Y (PVY) strains affecting potato with the ordinary strain PVYO declining and the recombinant strains PVYNTN and PVYN:O emerging in the United States. Multiple PVY strains are commonly found in potato fields and even in individual plants. Factors contributing to the emergence of the recombinant strains are not well defined but differential aphid transmission of strains from single and mixed infections may play a role. We found that the transmission efficiencies by Myzus persicae, the green peach aphid, of PVYNTN, PVYN:O, and PVYO varied depending on the potato cultivar serving as the virus source. Overall transmission efficiency was highest from sources infected with three virus strains, whereas transmission from sources infected with one or two virus strains was not significantly different. Two strains were concomitantly transmitted by individual aphids from many of the mixed-source combinations, especially if PVYO was present. Triple-strain infections were not transmitted by any single aphid. PVYO was transmitted most efficiently from mixed-strain infection sources. The data do not support the hypothesis that differential transmission of PVY strains by M. persicae is a major contributing factor in the emergence of recombinant PVY strains in the U.S. potato crop.

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Thanusuwannasak, Thanundorn, Jiratchaya Puenpa, Watchaporn Chuchaona, Sompong Vongpunsawad et Yong Poovorawan. « Emergence of multiple norovirus strains in Thailand, 2015–2017 ». Infection, Genetics and Evolution 61 (juillet 2018) : 108–12. http://dx.doi.org/10.1016/j.meegid.2018.03.021.

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Tanaka, Masatoshi. « Emergence of multidrug-resistant Neisseria gonorrhoeae strains circulating worldwide ». International Journal of Urology 19, n^o 2 (13 décembre 2011) : 98–99. http://dx.doi.org/10.1111/j.1442-2042.2011.02891.x.

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Morozumi, Miyuki, Keiko Hasegawa, Reiko Kobayashi, Nagako Inoue, Satoshi Iwata, Haruo Kuroki, Naohisa Kawamura et al. « Emergence of Macrolide-Resistant Mycoplasma pneumoniae with a 23S rRNA Gene Mutation ». Antimicrobial Agents and Chemotherapy 49, n^o 6 (juin 2005) : 2302–6. http://dx.doi.org/10.1128/aac.49.6.2302-2306.2005.

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ABSTRACT A total of 195 Mycoplasma pneumoniae strains were isolated from 2,462 clinical specimens collected between April 2002 and March 2004 from pediatric outpatients with respiratory tract infections. Susceptibilities to six macrolide antibiotics (ML), telithromycin, minocycline, levofloxacin, and sitafloxacin were determined by the microdilution method using PPLO broth. A total of 183 M. pneumoniae isolates were susceptible to all agents and had excellent MIC90s in the following order: 0.00195 μg/ml for azithromycin and telithromycin, 0.0078 μg/ml for clarithromycin, 0.0156 μg/ml for erythromycin, 0.0625 μg/ml for sitafloxacin, 0.5 μg/ml for minocycline, and 1 μg/ml for levofloxacin. Notably, 12 ML-resistant M. pneumoniae strains were isolated from patients with pneumonia (10 strains) or acute bronchitis (2 strains). These strains showed resistance to ML with MICs of ≥1 μg/ml, except to rokitamycin. Transition mutations of A2063G or A2064G, which correspond to A2058 and A2059 in Escherichia coli, in domain V on the 23S rRNA gene in 11 ML-resistant strains were identified. By pulsed-field gel electrophoresis typing, these strains were classified into groups I and Vb, as described previously (A. Cousin-Allery, A. Charron, B. D. Barbeyrac, G. Fremy, J. S. Jensen, H. Renaudin, and C. Bebear, Epidemiol. Infect. 124:103-111, 2000). These findings suggest that excessive usage of MLs acts as a trigger to select mutations on the corresponding 23S rRNA gene with the resultant occurrence of ML-resistant M. pneumoniae. Monitoring ML susceptibilities for M. pneumoniae is necessary in the future.

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Zhang, Rong, Dachuan Lin, Edward Wai-chi Chan, Danxia Gu, Gong-Xiang Chen et Sheng Chen. « Emergence of Carbapenem-Resistant Serotype K1 Hypervirulent Klebsiella pneumoniae Strains in China ». Antimicrobial Agents and Chemotherapy 60, n^o 1 (16 novembre 2015) : 709–11. http://dx.doi.org/10.1128/aac.02173-15.

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ABSTRACTWe report the emergence of five carbapenem-resistant K1 hypervirulentKlebsiella pneumoniae(hvKP) strains which caused fatal infections in hospital patients in Zhejiang Province, China, upon entry through surgical wounds. Genotyping results revealed the existence of three genetically related strains which exhibited a new sequence type, ST1797, and revealed that all strains harbored themagAandwcaGvirulence genes and a plasmid-borneblaKPC-2gene. These findings indicate that K1 hvKP is simultaneously hypervirulent, multidrug resistant, and transmissible.

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Zhu, Bolin, et Dong Qiu. « Dynamic analysis and optimal control of co-infection system under different outbreak times of mutant strains ». AIMS Allergy and Immunology 8, n^o 3 (2024) : 167–92. http://dx.doi.org/10.3934/allergy.2024009.

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<p>In epidemic prevention efforts, the emergence of new virus strains due to mutations greatly complicates the prediction and management of epidemics. Most of the current mathematical models of infectious diseases assume that the mutant strain and the original strain have the same outbreak time, which is obviously an ideal situation. In order to make the study more practical, we consider the general situation of outbreaks of mutated strains. At the same time, the optimal control strategy under different emergence time of mutant strains was proposed by using the optimal control theory and numerical simulation. This study provides a new theoretical framework for the dual strain competition model with different outbreak times. The final theoretical results and numerical simulation showed that although the emergence time of the mutant did not affect the final trend of the epidemic, it would affect the cost of prevention and control during the control period.</p>

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Tokarz, Rafal, Cadhla Firth, Shabir A. Madhi, Stephen R. C. Howie, Winfred Wu, Amadou Alpha Sall, Saddef Haq, Thomas Briese et W. Ian Lipkin. « Worldwide emergence of multiple clades of enterovirus 68 ». Journal of General Virology 93, n^o 9 (1 septembre 2012) : 1952–58. http://dx.doi.org/10.1099/vir.0.043935-0.

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Human enterovirus 68 (EV-D68) is a historically rarely reported virus linked with respiratory disease. In the past 3 years, a large increase in respiratory disease associated with EV-D68 has been reported, with documented outbreaks in North America, Europe and Asia. In several outbreaks, genetic differences were identified among the circulating strains, indicating the presence of multiple clades. In this report, we analyse archived and novel EV-D68 strains from Africa and the USA, obtained from patients with respiratory illness. Phylogenetic analysis of all EV-D68 sequences indicates that, over the past two decades, multiple clades of the virus have emerged and spread rapidly worldwide. All clades appear to be currently circulating and contributing to respiratory disease.

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Torrance, Lesley, et Michael E. Talianksy. « Potato Virus Y Emergence and Evolution from the Andes of South America to Become a Major Destructive Pathogen of Potato and Other Solanaceous Crops Worldwide ». Viruses 12, n^o 12 (12 décembre 2020) : 1430. http://dx.doi.org/10.3390/v12121430.

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The potato was introduced to Europe from the Andes of South America in the 16th century, and today it is grown worldwide; it is a nutritious staple food eaten by millions and underpins food security in many countries. Unknowingly, potato virus Y (PVY) was also introduced through trade in infected potato tubers, and it has become the most important viral pathogen of potato. Phylogenetic analysis has revealed the spread and emergence of strains of PVY, including strains causing economically important diseases in tobacco, tomato and pepper, and that the virus continues to evolve with the relatively recent emergence of new damaging recombinant strains. High-throughput, next-generation sequencing platforms provide powerful tools for detection, identification and surveillance of new PVY strains. Aphid vectors of PVY are expected to increase in incidence and abundance in a warmer climate, which will increase the risk of virus spread. Wider deployment of crop cultivars carrying virus resistance will be an important means of defence against infection. New cutting-edge biotechnological tools such as CRISPR and SIGS offer a means for rapid engineering of resistance in established cultivars. We conclude that in future, human activities and ingenuity should be brought to bear to control PVY and the emergence of new strains in key crops by increased focus on host resistance and factors driving virus evolution and spread.

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Gunnels, Tess, Ronald A. Shikiya, Taylor C. York, Alyssa J. Block et Jason C. Bartz. « Evidence for preexisting prion substrain diversity in a biologically cloned prion strain ». PLOS Pathogens 19, n^o 9 (5 septembre 2023) : e1011632. http://dx.doi.org/10.1371/journal.ppat.1011632.

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Prion diseases are a group of inevitably fatal neurodegenerative disorders affecting numerous mammalian species, including Sapiens. Prions are composed of PrPSc, the disease specific conformation of the host encoded prion protein. Prion strains are operationally defined as a heritable phenotype of disease under controlled transmission conditions. Treatment of rodents with anti-prion drugs results in the emergence of drug-resistant prion strains and suggest that prion strains are comprised of a dominant strain and substrains. While much experimental evidence is consistent with this hypothesis, direct observation of substrains has not been observed. Here we show that replication of the dominant strain is required for suppression of a substrain. Based on this observation we reasoned that selective reduction of the dominant strain may allow for emergence of substrains. Using a combination of biochemical methods to selectively reduce drowsy (DY) PrPSc from biologically-cloned DY transmissible mink encephalopathy (TME)-infected brain resulted in the emergence of strains with different properties than DY TME. The selection methods did not occur during prion formation, suggesting the substrains identified preexisted in the DY TME-infected brain. We show that DY TME is biologically stable, even under conditions of serial passage at high titer that can lead to strain breakdown. Substrains therefore can exist under conditions where the dominant strain does not allow for substrain emergence suggesting that substrains are a common feature of prions. This observation has mechanistic implications for prion strain evolution, drug resistance and interspecies transmission.

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Mello, A. F. S., R. K. Yokomi, U. Melcher, J. C. Chen, A. C. Wayadande et J. Fletcher. « Genetic Diversity of Spiroplasma citri Strains from Different Regions, Hosts, and Isolation Dates ». Phytopathology® 98, n^o 9 (septembre 2008) : 960–68. http://dx.doi.org/10.1094/phyto-98-9-0960.

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Spiroplasma citri, a phloem-limited pathogen, causes citrus stubborn disease (CSD). Losses due to CSD in California orchards have grown over the past decade. To investigate the possibility of introduction or emergence of a new strain, a study of genetic diversity among S. citri strains from various locations was conducted using random amplified polymorphism DNA-polymerase chain reaction (RAPD-PCR) of 35 strains cultured from 1980 to 1993, and of 35 strains cultured from 2005 to 2006. Analysis using 20 primer pairs revealed considerable diversity among strains. However, no unique genetic signatures were associated with recently collected strains compared with those collected 15 to 28 years ago, and no geographically associated pattern was distinguishable. S. citri strains from carrot and daikon radish contain some unique DNA fragments, suggesting some host plant influence. Multiple strains from single trees also showed genetic diversity. Sequencing of five RAPD bands that differed among strains showed that diversity-related gene sequences include virus fragments, and fragments potentially encoding a membrane lipoprotein, a DNA modification enzyme, and a mobilization element. No differences in colony morphology were observed among the strains. The lack of correlation between PCR patterns and isolation date or collection site is inconsistent with the hypothesis that recent infections are due to the introduction or emergence of novel pathogen strains.

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Johnson, Leonard B., Anilrudh A. Venugopal, Joan Pawlak et Louis D. Saravolatz. « Emergence of Community-Associated Methicillin-ResistantStaphylococcus aureusInfection Among Patients With End-Stage Renal Disease ». Infection Control & ; Hospital Epidemiology 27, n^o 10 (octobre 2006) : 1057–62. http://dx.doi.org/10.1086/507958.

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Objective.To evaluate the frequency of infections due to community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) strains among our patients with end-stage renal disease.Design.Prospective observational clinical and laboratory study of patients in 2005. Molecular features of isolates recovered from these patients were compared with those of isolates recovered in 2000 from patients with end-stage renal disease.Setting.A 600-bed urban academic medical center.Patients.Thirty-two patients with end-stage renal disease and MRSA infection at the time of hospitalization from 2005 were evaluated. For comparison, laboratory analysis was performed for 17 MRSA isolates recovered from patients with end-stage renal disease in 2000.Results.The patients from 2005 were more likely than the patients from 2000 to have infection with strains that carried the staphylococcal cassette chromosome (SCC)mectype IV complex (50% vs 11.8%; relative risk, 4.25 [95% confidence interval, 1.17-25.98];P= .012) and the Panton-Valentine leukocidin toxin genes (25% vs 0%;P= .038). Eight patients from 2005 were infected with a strain that is identical to MRSA clone USA300 in terms of molecular type and presence of SCCmectype IV and Panton-Valentine leukocidin genes. Among the patients from 2005, those infected with SCCmectype IV strains (ie, CA-MRSA strains) and those infected with SCCmectype II strains (ie, healthcare-associated MRSA [HA-MRSA] strains) were similar with respect to demographic characteristics, risk factors, and outcomes.Conclusions.We documented an increased proportion of infections with CA-MRSA strains, including clone USA300, among our population of patients undergoing dialysis. Patients infected with CA-MRSA strains and HA-MRSA strains were similar with respect to presenting illness and outcomes.

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Lee, Woojung, Min-Hee Kim, Soohyun Sung, Eiseul Kim, Eun Sook An, Seung Hwan Kim, Soon Han Kim et Hae-Yeong Kim. « Genome-Based Characterization of Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia coli (STEC/ETEC) Strains Isolated in South Korea, 2016–2020 ». Microorganisms 11, n^o 5 (15 mai 2023) : 1285. http://dx.doi.org/10.3390/microorganisms11051285.

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The global emergence of hybrid diarrheagenic E. coli strains incorporating genetic markers from different pathotypes is a public health concern. Hybrids of Shiga toxin-producing and enterotoxigenic E. coli (STEC/ETEC) are associated with diarrhea and hemolytic uremic syndrome (HUS) in humans. In this study, we identified and characterized STEC/ETEC hybrid strains isolated from livestock feces (cattle and pigs) and animal food sources (beef, pork, and meat patties) in South Korea between 2016 and 2020. The strains were positive for genes from STEC and ETEC, such as stx (encodes Shiga toxins, Stxs) and est (encodes heat-stable enterotoxins, ST), respectively. The strains belong to diverse serogroups (O100, O168, O8, O155, O2, O141, O148, and O174) and sequence types (ST446, ST1021, ST21, ST74, ST785, ST670, ST1780, ST1782, ST10, and ST726). Genome-wide phylogenetic analysis revealed that these hybrids were closely related to certain ETEC and STEC strains, implying the potential acquisition of Stx-phage and/or ETEC virulence genes during the emergence of STEC/ETEC hybrids. Particularly, STEC/ETEC strains isolated from livestock feces and animal source foods mostly exhibited close relatedness with ETEC strains. These findings allow further exploration of the pathogenicity and virulence of STEC/ETEC hybrid strains and may serve as a data source for future comparative studies in evolutionary biology.

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Weinstein, Robert A. « Endemic Emergence of Cephalosporin-Resistant Enterobacter : Relation to Prior Therapy ». Infection Control & ; Hospital Epidemiology 7, S2 (février 1986) : 120–23. http://dx.doi.org/10.1017/s0195941700065632.

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The “second” and “third” generation cephalosporins offer striking antimicrobial activity against a wide spectrum of Enterobacteriaceae. Nevertheless, mutants resistant to these drugs have emerged in both laboratory and clinical settings. For example, before the commercial availability of the third-generation agents, we treated three cardiac surgery patients for Enterobacter mediastinitis with aminoglycosides and high doses of cefamandole. In two, initial treatment failed due to emergence of strains that were not only resistant to cefamandole, but also to then experimental third-generation drugs. Despite such reports and in vitro studies of the mechanisms of resistance, the frequency with which broad-spectrum cephalosporin resistance develops in clinical practice is not clear. To help delineate this problem, we have reviewed our hospital's experience with Enterobacter strains resistant to newer cephalosporins (using cefamandole and cefotaxime as prototypes) and the relation of resistant strains to cephalosporin use, with special attention to our cardiac surgery patients.

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Zhang, J. X., A. G. Xue et J. T. Tambong. « Evaluation of Seed and Soil Treatments with Novel Bacillus subtilis Strains for Control of Soybean Root Rot Caused by Fusarium oxysporum and F. graminearum ». Plant Disease 93, n^o 12 (décembre 2009) : 1317–23. http://dx.doi.org/10.1094/pdis-93-12-1317.

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Fusarium root rot is an important disease of soybean in Ontario, Canada. This study is to select antagonistic bacterial agents as effective alternatives to chemical pesticides for the control of root rots caused by Fusarium oxysporum and F. graminearum. Twenty-two Bacillus subtilis strains from soybean and corn roots were tested in dual cultures for inhibition of mycelial growth of F. oxysporum and F. graminearum. All strains significantly reduced mycelial growth of F. oxysporum by approximately 17 to 48% and of F. graminearum by 10 to 32%. Ten B. subtilis strains selected based on their larger fungal inhibition zones were evaluated against macroconidial germination. These strains inhibited the spore germination of F. oxysporum by 20 to 48% and of F. graminearum by 14 to 32% in cell-free filtrates. Under greenhouse conditions, the efficacy of seed and soil treatments with B. subtilis strains against the two Fusarium root rot pathogens was evaluated based on root rot severity, seedling emergence, plant height, and root dry weight. Six B. subtilis strains (SB01, SB04, SB23, SB24, SB28, and SB33) from soybean roots and two strains (CB01 and CH22) from corn roots significantly reduced the severity of the two Fusarium root rots in seed or soil treatments. Strains SB01, SB04, SB23, and SB24 were the most effective treatments against both pathogens in either seed or soil treatment. When applied as seed treatments, these four strains reduced root rot severity by 43 to 63% and increased emergence by 13 to 17%, plant height by 9 to 18%, and root dry weight by 8.4 to 19%. When used as soil treatments, they reduced root rot severity by 68 to 74% and increased emergence by 14 to 18%, plant height by 11 to 23%, and root dry weight by 16 to 24%. These results suggest that the novel strains of B. subtilis identified in this research can be effective alternatives to fungicides in managing Fusarium root rots of soybean, and a greater level of efficacy may be achieved when they were used as soil treatments than seed treatments.

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Galiakbarova, Alsu Anvarovna. « Factors affecting the emergence of antibiotic-resistant enterobacteria ». Vrač skoroj pomoŝi (Emergency Doctor), n^o 1 (1 janvier 2021) : 56–65. http://dx.doi.org/10.33920/med-02-2101-05.

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The biological properties of the archival strains of Escherichia were studied using automatic analyzers Vitek 2 and Sensititre. In addition, the antibiotic sensitivity, genetic identification, and enzymatic properties were determined.

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Reed, Joseph M., Stewart G. Gardner, Nagendra N. Mishra, Arnold S. Bayer et Greg A. Somerville. « Metabolic interventions for the prevention and treatment of daptomycin non-susceptibility in Staphylococcus aureus ». Journal of Antimicrobial Chemotherapy 74, n^o 8 (10 mai 2019) : 2274–83. http://dx.doi.org/10.1093/jac/dkz194.

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AbstractBackgroundA major developing problem in the treatment of Staphylococcus aureus infections is the emergence of resistance during treatment with daptomycin. Previous metabolomic analyses of isogenic S. aureus strains prior to and after evolution into a daptomycin non-susceptible (DapNS) state provided important metabolic information about this transition (e.g. perturbations of the tricarboxylic acid cycle).ObjectivesTo assess the significance of these metabolic changes, in vitro susceptibility to daptomycin was determined in daptomycin-susceptible (DapS) and DapNSS. aureus strains cultivated with metabolic inhibitors targeting these changes.MethodsOnly inhibitors that are approved for use in humans were chosen (i.e. fosfomycin, valproate, trimetazidine and 6-mercaptopurine) to assess the importance of metabolic pathways for daptomycin non-susceptibility. The ability of these inhibitors to forestall the emergence of DapNS strains was also assessed.ResultsThe combination of daptomycin and fosfomycin synergistically killed both DapS and DapNS strains in vitro and enhanced the in vivo outcome against a DapNS strain in experimental endocarditis. Interestingly, fosfomycin acts on the peptidoglycan biosynthetic enzyme UDP-N-acetylglucosamine enolpyruvyl transferase (MurA); however, it also had a significant effect on the enzymatic activity of enolase, an essential enzyme in S. aureus. While fosfomycin acted synergistically with daptomycin, it failed to prevent the in vitro evolution of daptomycin non-susceptibility. In contrast, trimetazidine, an anti-angina drug that stimulates glucose oxidation, abolished the ability of DapSS. aureus strains to transition to a DapNS state.ConclusionsThese data reveal that metabolic adaptations associated with DapNS strains can be targeted to prevent the emergence of and/or reverse pre-existing resistance to daptomycin.

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SINGH, P., M. CHHABRA, P. SHARMA, R. JAISWAL, G. SINGH, V. MITTAL, A. RAI et S. VENKATESH. « Molecular epidemiology of Crimean-Congo haemorrhagic fever virus in India ». Epidemiology and Infection 144, n^o 16 (15 août 2016) : 3422–25. http://dx.doi.org/10.1017/s0950268816001886.

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SUMMARYCrimean-Congo haemorrhagic fever (CCHF) is an emerging zoonotic disease in India which is prevalent in neighbouring countries. CCHF virus (CCHFV) is a widespread tick-borne virus which is endemic in Africa, Asia, Eastern Europe and the Middle East. In the present study, samples of clinically suspected human cases from different areas of northern-western India were tested for the presence of CCHFV by RT–PCR through amplification of nucleocapsid (N) gene of CCHFV. Positive samples were sequenced to reveal the prevailing CCHFV genotype(s) and phylogenetic relatedness. A phylogenetic tree revealed the emergence of diverse strains in the study region showing maximum identity with the Pakistan, Afghanistan and Iran strains, which was different from earlier reported Indian strains. Our findings reveal for the first time the emergence of the Asia 1 group in India; while earlier reported CCHFV strains belong to the Asia 2 group.

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Ankita, Lokhande, et Deshpande Aarti. « Screening of Ayurvedic Drugs against Multidrug Resistant Staphylococcus aureus ». International Journal of Current Microbiology and Applied Sciences 13, n^o 9 (10 septembre 2024) : 165–72. https://doi.org/10.20546/ijcmas.2024.1309.018.

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Emergence of resistance against commonly used antibiotics has become a serious global concern. The emergence of antimicrobial or multidrug resistance to standard antibiotics associated with Staphylococcus aureus causes a benefit of interest to ayurvedic drugs as an effective means of control. Acetone, ethanol, methanol, and aqueous hot and cold extracts of nine ayurvedic churnas viz Manjishta, Kadunimchal, Neempati, Behada, Arjusal, Trikatu, Dhataki, Jati and Marich were tested for their antibacterial action against three multidrug resistant Staphylococcus aureus strains isolated from clinical samples. Ethanol and acetone extracts of Kadunimchal, behada & Jati were found bactericidal against all three strains. Antibiogram studies revealed the antibacterial pattern of many churnas against the MDR Staphylococcus aureus strains and potential use of ayurvedic formulations against infections caused by Staphylococcus aureus.

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Oliveira, Gabriel S., Raquel P. Costa, Paula Gomes, Maria Salomé Gomes, Tânia Silva et Cátia Teixeira. « Antimicrobial Peptides as Potential Anti-Tubercular Leads : A Concise Review ». Pharmaceuticals 14, n^o 4 (2 avril 2021) : 323. http://dx.doi.org/10.3390/ph14040323.

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Despite being considered a public health emergency for the last 25 years, tuberculosis (TB) is still one of the deadliest infectious diseases, responsible for over a million deaths every year. The length and toxicity of available treatments and the increasing emergence of multidrug-resistant strains of Mycobacterium tuberculosis renders standard regimens increasingly inefficient and emphasizes the urgency to develop new approaches that are not only cost- and time-effective but also less toxic. Antimicrobial peptides (AMP) are small cationic and amphipathic molecules that play a vital role in the host immune system by acting as a first barrier against invading pathogens. The broad spectrum of properties that peptides possess make them one of the best possible alternatives for a new “post-antibiotic” era. In this context, research into AMP as potential anti-tubercular agents has been driven by the increasing danger revolving around the emergence of extremely-resistant strains, the innate resistance that mycobacteria possess and the low compliance of patients towards the toxic anti-TB treatments. In this review, we will focus on AMP from various sources, such as animal, non-animal and synthetic, with reported inhibitory activity towards Mycobacterium tuberculosis.

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Wang, Eryu, Aaron C. Brault, Ann M. Powers, Wenli Kang et Scott C. Weaver. « Glycosaminoglycan Binding Properties of Natural Venezuelan Equine Encephalitis Virus Isolates ». Journal of Virology 77, n^o 2 (15 janvier 2003) : 1204–10. http://dx.doi.org/10.1128/jvi.77.2.1204-1210.2003.

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ABSTRACT Equine-virulent, epidemic/epizootic strains of Venezuelan equine encephalitis (VEE) virus (VEEV) arise via mutation of progenitor enzootic strains that replicate poorly in equines. Sequencing studies have implicated positively charged amino acids on the surface of the E2 envelope glycoprotein in the acquisition of equine virulence and viremia potential, suggesting that changes in binding to cell surface glycosaminoglycans (GAGs) may mediate VEE emergence. Therefore, we evaluated the binding of natural enzootic and epizootic VEEV isolates to Chinese hamster ovary (CHO) cells expressing normal, high levels of GAGs as well as to mutant CHO cells lacking GAG expression. Binding to GAGs was not consistently associated with the epizootic phenotype, and cell culture passages resulted in increased GAG binding. The low levels of GAG binding exhibited by some low-passage, equine-virulent subtype IC VEEV strains indicate that the positive-charge E2 mutations implicated in VEE subtype IC emergence are not artifacts of laboratory passage and suggest that GAG binding does not play a major role in mediating VEE emergence. The increased GAG binding exhibited by VEEV strain CPA201 from the 1993 Mexican epizootic, when compared to that of closely related enzootic subtype IE strains, was shown to result from a Glu-to-Lys mutation at position 117 of the E2 envelope glycoprotein.

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Xiu, Leshan, Qianqin Yuan, Yamei Li, Chi Zhang, Lingli Tang et Junping Peng. « Emergence of ceftriaxone-resistant Neisseria gonorrhoeae strains harbouring a novel mosaic penA gene in China ». Journal of Antimicrobial Chemotherapy 75, n^o 4 (3 janvier 2020) : 907–10. http://dx.doi.org/10.1093/jac/dkz530.

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Abstract Objectives The continuous emergence of ceftriaxone-resistant Neisseria gonorrhoeae strains threatens the effectiveness of current treatment regimens for gonorrhoea. The objective of the present study was to characterize three ceftriaxone-resistant N. gonorrhoeae strains with a novel mosaic penA allele isolated in China. Methods Three ceftriaxone-resistant Neisseria gonorrhoeae strains (GC150, GC161 and GC208) isolated in 2017 were characterized by N. gonorrhoeae multiantigen sequence typing (NG-MAST), MLST and N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR). Recombination analyses were performed using the SimPlot software. Results Three strains had the same antibiotic resistance profiles, with resistance to ceftriaxone (MIC 0.5 mg/L), ciprofloxacin (MIC 8.0 mg/L), penicillin (MIC 2.0 mg/L) and tetracycline (MIC 2.0–8.0 mg/L). STs were assigned as MLST7360, NG-MAST14292 and NG-STAR1611/NG-STAR1612. The penA gene of these three strains differed from previous ceftriaxone-resistant gonococcal strains and harboured a novel mosaic allele (penA-121.001). Like N. gonorrhoeae FC428, a widely disseminated ceftriaxone-resistant strain that was initially described in Japan in 2015, all strains also possessed substitutions A311V and T483S in PBP2, which are associated with resistance to ceftriaxone. Potential recombination events were detected in penA between N. gonorrhoeae strain FC428 and commensal Neisseria species. Our results provide further evidence that the commensal Neisseria species (Neisseria cinerea and Neisseria perflava) can serve as a reservoir of ceftriaxone resistance-mediating penA sequences in clinical gonococcal strains. Conclusions The emergence of such strains may be the result of the interspecies recombination of penA genes between N. gonorrhoeae strain FC428 and commensal Neisseria species.

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Kazemi, M., R. Kasra Kermanshahi, E. Heshmat Dehkordi, F. Payami et M. Behjati. « Resistance Index of Penicillin-Resistant Bacteria to Various Physicochemical Agents ». ISRN Microbiology 2012 (31 janvier 2012) : 1–6. http://dx.doi.org/10.5402/2012/789474.

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Widespread use of various antimicrobial agents resulted in the emergence of bacterial resistance. Mechanisms like direct efflux, formation, and sequestration of metals and drugs in complexes and antiporter pumps are some examples. This investigation aims to investigate the resistance pattern of penicillin-resistant bacterial strains to some physicochemical agents. Sensitivity/resistance pattern of common bacterial strains to antimicrobial agents were evaluated by disk diffusion assay. Broth and agar dilution method were used for determination of minimum inhibitory concentration and minimal bactericidal concentration. The impact of UV ray on the bacterial growth under laminar flow hood was measured using photonmeter. Our data demonstrates that the most prevalent metal resistance was against arsenate (95.92%), followed by cadmium (52.04%) and mercury (36.73%). There was significant difference between cetrimide resistances among studied microbial strains especially for P. aeruginosa (). High rate of pathogen resistance to various antibacterial agents in our study supports previously published data. This great rate of bacterial resistance is attributed to the emergence of defense mechanisms developed in pathogens. The higher general bacterial resistance rate among Staphylococcus strains rather than E. coli and P. aeruginosa strains draws attention towards focusing on designing newer therapeutic compounds for Staphylococcus strains.

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Zain, Nor Azimah Mohd, Nurezzaati Othman et Mohd Suardi Suhaimi. « The Emergence of Multidrug Resistance Bacteria at Kong Kong River, Johor, Malaysia : Preliminary Study ». Proceedings of the Singapore National Academy of Science 13, n^o 01 (décembre 2019) : 3–16. http://dx.doi.org/10.1142/s2591722619400015.

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Kampung Kong Kong Laut is a fishing village located in Kong Kong, Masai, Johor, Malaysia that is one of the main seafood producers in the area. The status quo on the emergence of the multidrug resistance bacteria in Johor is unknown. Thus, this study aims at investigating the emergence of multidrug resistance bacteria in the water sample form the selected site. Besides that, the resistance of the isolated bacteria toward antibiotics were studied against selected antibiotics, such as ampicilin, bacitracin, chloramphenicol, erythromycin, kanamycin, nalidixic acid and streptomycin. A total of 18 different strains were succesfully isolated and based on the morphological and conventional biochemical tests, the isolates were identified as Escherichia sp., Bacillus sp., Pseudomonas sp., Staphylococcus sp., Proteus sp., Helicobacter sp. and Serratia sp. From this study, it was found that all the 61% of the bacteria (11 strains) were resistant toward all the antibiotic tested. The rest of the strains (38% or seven strains) showed resistance toward at least one antibiotic. All the seven strains showed different range of sensitivity toward bacitracin, chloramphenicol, erythromycin, kanamycin and streptomycin.

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Enebak, S. A. « Rhizobacteria Isolated from Loblolly Pine Seedlings Mediate Growth-Promotion of Greenhouse-Grown Loblolly, Slash, and Longleaf Pine Seedlings ». Forest Science 51, n^o 6 (1 décembre 2005) : 541–45. http://dx.doi.org/10.1093/forestscience/51.6.541.

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Abstract Loblolly (Pinus taeda L.), slash (Pinus elliottii Engelm.), and longleaf pine (Pinus palustris Mill.) seeds were inoculated in the greenhouse with rhizobacteria recovered from 4-month-old bareroot loblolly pine seedlings. Emergence and seedling densities were determined at 3- and 8-week intervals after sowing, respectively, with root and shoot biomass measured at 12 weeks. All bacterial strains significantly increased the speed of seedling emergence relative to untreated loblolly and slash pine seeds, while five strains significantly slowed longleaf germination. For loblolly and slash pine, there were no differences in percentage germination when comparing treated and untreated seed. However, all bacterial strains significantly reduced longleaf germination over nontreated seed. Treatment with rhizobacteria had significant positive and negative effects on seedling growth and biomass, depending on the tree species and bacteria isolate used. Five of the eight bacterial isolates tested increased shoot length of loblolly pine seedlings, whereas one strain increased above- and belowground biomass. Slash pine seedlings experienced growth increases with three bacterial strains. However, two bacterial strains, ALA-41G and ALA-54G, resulted in shorter slash pine shoots. Only strain ALA-3G increased shoot biomass of longleaf pine over nontreated longleaf seed. Increased seedling emergence and growth promotion by rhizobacteria collected from Pinus sp. is a potential useful tool for management of these forest species. The effect may be species-specific and the use of bacteria in forest nurseries for growth promotion will need to take this into account. FOR. SCI. 51(6):541–545.

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Schjørring, Susanne, et Karen A. Krogfelt. « Assessment of Bacterial Antibiotic Resistance Transfer in the Gut ». International Journal of Microbiology 2011 (2011) : 1–10. http://dx.doi.org/10.1155/2011/312956.

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We assessed horizontal gene transfer between bacteria in the gastrointestinal (GI) tract. During the last decades, the emergence of antibiotic resistant strains and treatment failures of bacterial infections have increased the public awareness of antibiotic usage. The use of broad spectrum antibiotics creates a selective pressure on the bacterial flora, thus increasing the emergence of multiresistant bacteria, which results in a vicious circle of treatments and emergence of new antibiotic resistant bacteria. The human gastrointestinal tract is a massive reservoir of bacteria with a potential for both receiving and transferring antibiotic resistance genes. The increased use of fermented food products and probiotics, as food supplements and health promoting products containing massive amounts of bacteria acting as either donors and/or recipients of antibiotic resistance genes in the human GI tract, also contributes to the emergence of antibiotic resistant strains. This paper deals with the assessment of antibiotic resistance gene transfer occurring in the gut.

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Hafeez, F. Y., M. E. Safdar, A. U. Chaudhry et K. A. Malik. « Rhizobial inoculation improves seedling emergence, nutrient uptake and growth of cotton ». Australian Journal of Experimental Agriculture 44, n^o 6 (2004) : 617. http://dx.doi.org/10.1071/ea03074.

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Experiments were conducted to determine the growth promoting activities of various rhizobia in cotton (Gossypium hirsutum L.) under growth room conditions. Seeds of 4 cotton cultivars were inoculated with 4-indole-3-acetic acid producing selected (Brady) rhizobium strains and Azotobacter plant growth promoting rhizobacteria strains, included as a positive control. Growth responses to inoculation exhibited bacterial strain-cotton cultivar specificity and also included increase in rate of seedling emergence by 3–9%. Shoot dry weight, biomass and N uptake were increased by 48, 75 and 57%, respectively, due to inoculation with both the Rhizobium leguminosarum bv. trifolii E11 and Azotobacter sp. S8, whereas, strain E11 also increased root dry weight, root length and area by 248, 332 and 283%, respectively. K+ and Ca2+ uptake was also increased by 2–21% and 9–14%, respectively, due to rhizobial inoculation. The results also showed that (Brady) rhizobium strains promoted cotton growth through efficient nutrient uptake, which was mainly related to increased root growth due to the effect of IAA produced by these strains. However, growth promotion by Azotobacter sp. S8, in addition to 4-indole-3-acetic acid production, might also involve biological N2 fixation by this rhizobacterial strain at some stage during its growth.

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Shah, Pir Tariq, Amina Nawal Bahoussi, Caiting Yang, Guanhan Yao, Li Dong, Changxin Wu et Li Xing. « Genetic Characteristics and Phylogeographic Dynamics of Lagoviruses, 1988–2021 ». Viruses 15, n^o 4 (23 mars 2023) : 815. http://dx.doi.org/10.3390/v15040815.

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Rabbit haemorrhagic disease virus (RHDV), European brown hare syndrome virus (EBHSV), rabbit calicivirus (RCV), and hare calicivirus (HaCV) belong to the genus Lagovirus of the Caliciviridae family that causes severe diseases in rabbits and several hare (Lepus) species. Previously, Lagoviruses were classified into two genogroups, e.g., GI (RHDVs and RCVs) and GII (EBHSV and HaCV) based on partial genomes, e.g., VP60 coding sequences. Herein, we provide a robust phylogenetic classification of all the Lagovirus strains based on full-length genomes, grouping all the available 240 strains identified between 1988 and 2021 into four distinct clades, e.g., GI.1 (classical RHDV), GI.2 (RHDV2), HaCV/EBHSV, and RCV, where the GI.1 clade is further classified into four (GI.1a–d) and GI.2 into six sub-clades (GI.2a–f). Moreover, the phylogeographic analysis revealed that the EBHSV and HaCV strains share their ancestor with the GI.1, while the RCV shares with the GI.2. In addition, all 2020–2021 RHDV2 outbreak strains in the USA are connected to the strains from Canada and Germany, while RHDV strains isolated in Australia are connected with the USA-Germany haplotype RHDV strain. Furthermore, we identified six recombination events in the VP60, VP10, and RNA-dependent RNA polymerase (RdRp) coding regions using the full-length genomes. The amino acid variability analysis showed that the variability index exceeded the threshold of 1.00 in the ORF1-encoded polyprotein and ORF2-encoded VP10 protein, respectively, indicating significant amino acid drift with the emergence of new strains. The current study is an update of the phylogenetic and phylogeographic information of Lagoviruses that may be used to map the evolutionary history and provide hints for the genetic basis of their emergence and re-emergence.

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Arista, Serenella, Giovanni M. Giammanco, Simona De Grazia, Stefania Ramirez, Concetta Lo Biundo, Claudia Colomba, Antonio Cascio et Vito Martella. « Heterogeneity and Temporal Dynamics of Evolution of G1 Human Rotaviruses in a Settled Population ». Journal of Virology 80, n^o 21 (23 août 2006) : 10724–33. http://dx.doi.org/10.1128/jvi.00340-06.

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ABSTRACT A rotavirus sample collection from 19 consecutive years was used to investigate the heterogeneity and the dynamics of evolution of G1 rotavirus strains in a geographically defined population. Phylogenetic analysis of the VP7 gene sequences of G1P[8] human rotavirus strains showed the circulation of a heterogeneous population comprising three lineages and seven sublineages. Increases in the circulation of G1 rotaviruses were apparently associated with the introduction of novel G1 strains that exhibited multiple amino acid changes in antigenic regions involved in rotavirus neutralization compared to the strains circulating in the previous years. The emergence and/or introduction of G1 antigenic variants might be responsible for the continuous circulation of G1 rotaviruses in the local population, with the various lineages and sublineages appearing, disappearing, or cocirculating in an alternate fashion under the influence of immune-pressure mechanisms. Sequence analysis of VP4-encoding genes of the G1 strains revealed that the older strains were associated with a unique VP4 lineage, while a novel VP4 lineage emerged after 1995. The introduction of human rotavirus vaccines might alter the forces and balances that drive rotavirus evolution and determine the spread of novel strains that are antigenically different from those included in the vaccine formulations. The continuous emergence of VP7-VP4 gene combinations in human rotavirus strains should be taken into consideration when devising vaccination strategies.

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Rump, Lydia V., Markus Fischer et Narjol González-Escalona. « Different IS629Transposition Frequencies Exhibited by Escherichia coli O157:H7 Strains in the Stepwise Evolutionary Model ». Applied and Environmental Microbiology 77, n^o 14 (27 mai 2011) : 5030–33. http://dx.doi.org/10.1128/aem.00249-11.

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ABSTRACTThe insertion sequence IS629, which is highly prevalent inEscherichia coliO157:H7 genomes, was found to be absent in O157:H− strains, which are on a divergent pathway in the emergence of O157:H7. Although O157:H− is deficient in IS629, it permits IS629transposition, with an excision frequency higher than that of ancestral O55:H7 strains but significantly lower than that of pathogenic O157:H7 strains.

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Yu, Zheng-Hao, Yan-Ping Zhang, Xing-Ge Lan, Ya-Nan Wang, Rong-Rong Guo, Kai Li, Li Gao et al. « Differences in Pathogenicity and Vaccine Resistance Discovered between Two Epidemic Strains of Marek’s Disease Virus in China ». Viruses 15, n^o 4 (11 avril 2023) : 945. http://dx.doi.org/10.3390/v15040945.

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Despite highly effective vaccines, Marek’s disease (MD) causes great economic loss to the poultry industry annually, largely due to the continuous emergence of new MD virus (MDV) strains. To explore the pathogenic characteristics of newly emerged MDV strains, we selected two strains (AH/1807 and DH/18) with clinically different pathotypes. We studied each strain’s infection process and pathogenicity and observed differences in immunosuppression and vaccine resistance. Specific pathogen-free chickens, unvaccinated or vaccinated with CVI988, were challenged with AH/1807 or DH/18. Both infections induced MD damage; however, differences were observed in terms of mortality (AH/1807: 77.8%, DH/18: 50%) and tumor rates (AH/1807: 50%, DH/18: 33.3%). The immune protection indices of the vaccine also differed (AH/1807: 94.1, DH/18: 61.1). Additionally, while both strains caused interferon-β and interferon-γ expression to decline, DH/18 infection caused stronger immunosuppression than AH/1807. This inhibition persisted even after vaccination, leading to increased replication of DH/18 that ultimately broke through vaccine immune protection. These results indicate that both strains have different characteristics, and that strains such as DH/18, which cause weaker pathogenic damage but can break through vaccine immune protection, require further attention. Our findings increase the understanding of the differences between epidemic strains and factors underlying MD vaccination failure in China.

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Neofytos, D., B. Kuhn, S. Shen, X. Hua Zhu, D. Jungkind et P. Flomenberg. « Emergence of Staphylococcal Cassette ChromosomemecType IV Methicillin-ResistantStaphylococcus aureusas a Cause of Ventilator-Associated Pneumonia ». Infection Control & ; Hospital Epidemiology 28, n^o 10 (octobre 2007) : 1206–9. http://dx.doi.org/10.1086/520746.

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Staphylococcal cassette chromosomemec(SCCmec) type IV methicillin-resistantStaphylococcus aureus(MRSA) strains were identified in 8 (19.5%) of 41 consecutive patients with MRSA ventilator-associated pneumonia (VAP) in this retrospective, observational study. There were no significant differences in VAP severity and crude mortality rates between patients with SCCmectype II strains and patients with SCCmectype IV strains.

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Song, Jae-Hoon, Keiichi Hiramatsu, Ji Yoeun Suh, Kwan Soo Ko, Teruyo Ito, Maria Kapi, Sungmin Kiem et al. « Emergence in Asian Countries of Staphylococcus aureus with Reduced Susceptibility to Vancomycin ». Antimicrobial Agents and Chemotherapy 48, n^o 12 (décembre 2004) : 4926–28. http://dx.doi.org/10.1128/aac.48.12.4926-4928.2004.

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ABSTRACT To investigate the prevalence of Staphylococcus aureus with reduced susceptibility to vancomycin among methicillin-resistant S. aureus (MRSA) strains in Asian countries, a total of 1,357 clinical isolates of MRSA collected from 12 Asian countries were screened by using brain heart infusion agar plates containing 4 mg of vancomycin per liter. The presence of strains that were heterointermediately resistant to vancomycin (hVISA) was confirmed by population analysis. Of 347 (25.6%) MRSA isolates that grew on the screening agar plates, 58 isolates (4.3%) were hVISA. hVISA strains were found in India, South Korea, Japan, the Philippines, Singapore, Thailand, and Vietnam. However, neither vancomycin-intermediate S. aureus nor vancomycin-resistant S. aureus isolates were found among MRSA isolates from Asian countries in this survey.

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Simor, Andrew E., Anita Rachlis, Lisa Louie, Janet Goodfellow et Marie Louie. « Emergence of Penicillin-ResistantStreptococcus Pneumoniaein Southern Ontario, 1993–94 ». Canadian Journal of Infectious Diseases 6, n^o 3 (1995) : 157–60. http://dx.doi.org/10.1155/1995/657246.

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Objective: To determine the prevalence of resistance ofStreptococcus pneumoniaeto penicillin and other antimicrobial agents in metropolitan Toronto.Design: Consecutive pneumococcal isolates from different patients were obtained from two private community-based laboratories and from patients assessed in the emergency department of a tertiary-care teaching hospital in Toronto, Ontario between June and December 1993, and between March and October 1994. In vitro susceptibility testing was done by broth microdilution in accordance with National Committee for Clinical Laboratory Standards guidelines.Results: Twenty (7.3±3.1%) of 274 pneumococcal isolates were resistant to penicillin; six (30%) isolates had high-level resistance (minimal inhibitory concentration [mic] 2.0 μg/mL or greater); and 14 isolates had intermediate resistance (mic0.1 to 1.0 μg/mL). Penicillin-resistant strains were also frequently resistant to tetracycline (55%), cotrimoxazole (50%), erythromycin (40%) and cefuroxime (35%). Resistant strains comprised several serotypes: 19F (six isolates), 9V (three), 23F (three), and one each of 6A, 6B, 14, and 19A; four isolates were nontypeable.Conclusions: There has been a recent emergence of penicillin-resistantS pneumoniaein southern Ontario. National and regional surveillance is warranted to determine the extent of the problem elsewhere in Canada.

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Boudet, Agathe, Alexandre Jay, Catherine Dunyach-Remy, Raphaël Chiron, Jean-Philippe Lavigne et Hélène Marchandin. « In-Host Emergence of Linezolid Resistance in a Complex Pattern of Toxic Shock Syndrome Toxin-1-Positive Methicillin-Resistant Staphylococcus aureus Colonization in Siblings with Cystic Fibrosis ». Toxins 13, n^o 5 (28 avril 2021) : 317. http://dx.doi.org/10.3390/toxins13050317.

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Methicillin-resistant Staphylococcus aureus (MRSA) can cause chronic lung infections in patients with Cystic Fibrosis (CF). One option for managing them is the use of linezolid. We hereby report the in-host emergence of linezolid resistance (LR) in MRSA in CF siblings via a population analysis. A collection of 171 MRSA strains from 68 samples were characterized by determining their linezolid Minimal Inhibitory Concentrations (MICs), analyzing the locus of staphylococcal protein A (spa) and whole genome sequencing. Courses of linezolid were retraced. Strains belonged to three spa types (t002, t045, t127) and two sequence types (ST1, ST5). Emergence of LR occurred under treatment, one year apart in both siblings, in the CC5-MRSA-I Geraldine clone harboring the toxic shock syndrome toxin-1-encoding gene. Resistance was related to a G2576T substitution present in a variable number of 23S rRNA gene copies. Susceptible and resistant strains were co-isolated within samples. Single Nucleotide Polymorphism-based analysis revealed complex colonizations by highly diversified, clonally related populations. LR remains rare in MRSA and there are very few longitudinal analyses documenting its emergence. Analyzing a large MRSA collection revealed new aspects of LR emergence: it emerges in specific subclonal lineages resulting from adaptive diversification of MRSA in the CF lung and this heterogeneity of intra-sample resistance may contribute to compromising antibiotic management.

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