Dissertations / Theses on the topic 'Aminoglycoside antibiotics'
To see the other types of publications on this topic, follow the link: Aminoglycoside antibiotics.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Aminoglycoside antibiotics.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Zhu, Hongkun. "Studies of Aminoglycoside Antibiotics." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462802472.
Full text
2
Yung, Man Wah. "Aminoglycoside ototoxicity." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235543.
Full text
3
Wang, Hai. "Design, synthesis and RNA binding of aminoglycoside antibiotics /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9820848.
Full text
4
McKay, Geoffrey A. "Characterization of aminoglycoside phosphotransferase APH(3')-IIIa : an enterococcal enzyme conferring resistance to aminoglycoside antibiotics /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0034/NQ66223.pdf.
Full text
5
Perez, Fernandez Déborah. "Aminoglycoside antibiotics to selectively target bacterial 16S ribosomal RNA /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17284.
Full text
6
Ball, J. M. "Antibiotic production and inactivation by a producing organism." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234469.
Full text
7
Nessim, Gergawy Mourad A. "Effects of aminoglycoside antibiotics on intracellular processes in cerebral vasospasm." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22646.pdf.
Full text
8
Savic, Miloje. "Structural basis of aminoglycoside antibiotics resistance through ribosomal RNA methylation." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503020.
Full text
9
Zent, Clive Steven, and Clive Steven Zent. "The use of aminoglycoside antibiotic therapy in neutropaenic patients with haematological disease." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/24969.
Full textAbstract:
The use of aminoglycosides in the treatment of the febrile neutropaenic patient with haematological disease is difficult and often suboptimal. This study reviews the available literature to establish therapeutic guidelines in this population and then reports the use of a Bayesian statistics based predictive model to implement and manage therapy in 10 patients. A review of the literature on aminoglycoside Pharmacology and clinical use is essential to determine therapeutic guidelines for this population. Aminoglycosides are amino sugars in glycosidic linkage and are polycations at physiological PH. The antibiotic effect is mediated through inhibition of protein synthesis and disruption of cell membrane integrity. Principal use is in treatment of Gram negative infection although aminoglycosides have activity against some Gram positive organisms including staphylococci. Aminoglycosides are inactive against anaerobes. Acquired resistance is mediated by bacterial enzymatic drug metabolism. Aminoglycosides are nephro- and ototoxic, this is the major constraint in clinical use.
10
Mikkelsen, Helga. "Influence of growth mode and aminoglycoside antibiotics on Pseudomonas aeruginosa physiology." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611950.
Full text
11
Fan, Q. "Genetic and biochemical studies of the biosynthesis of glycopeptide and aminoglycoside antibiotics." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598931.
Full textAbstract:
My project explored the biosynthesis of teicoplanin and neomycin as representatives of glycopeptides and aminoglycosides respectively, with a focus on the characterisation of the biosynthetic enzymes and the development of methods for targeted gene disruption in the producer strains. Both Actinoplanes teichomyceticus ATCC 31121, the teicoplanin producer, and Streptomyces fradiae NCIMB 8233, the neomycin producer, were successfully conjugated. This allowed in vivo study of specific enzymes involved in the biosynthetic pathway. Several aspects of teicoplanin biosynthesis were studied: first, the timing and the mechanism of β-hydroxylation of the tyrosine monomer in the backbone of teicoplanin; secondly, the role of the uncharacterised X-domain in the last module of NRPS; and finally, the enzyme responsible for deacetylation of the N-acetyl-glucosaminyl moiety attached to the fourth amino acid of the heptapeptide. Late-stage neomycin biosynthesis, including steps of glycosylation, deacetylation and O-ribosylation, was studied using both in vivo and in vitro approaches. Two glycosyltransferases and one deacetylase were characterised through heterologous expression in Escherichia coli and gene inactivation in S. fradiae. Feeding pathway intermediates to the mutants revealed the possibility of the existence of an inducible second copy of at least some of the biosynthesic enzymes.
12
Bryant, Jane. "Effects of aminoglycoside antibiotics on hair-bundle development and mutant hair cells." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418404.
Full text
13
Oguejiofor, Wilson. "Investigating the delivery of antimicrobial proteins and aminoglycoside antibiotics to the airways." Thesis, Aston University, 2013. http://publications.aston.ac.uk/20895/.
Full textAbstract:
Biopharmaceuticals are finding wide applications in the management of diverse disease conditions. Pulmonary delivery of proteins may constitute an effective and efficient non-invasive alternative to parenteral delivery, which is currently the main route of administration of biopharmaceutical drugs. A particular area, in which pulmonary delivery of peptides and proteins may find ready application, is in the local delivery of antimicrobial peptides and proteins to the airway, a measure that could potentially bring about improvements to currently available antipseudomonal therapies. This thesis has therefore sought to develop inhalable antimicrobial proteins in combination with antibiotics that have particularly good antimicrobial activity against Pseudomonas aeruginosa infections in the respiratory tract of people with cystic fibrosis (CF). Through process optimisation, a suitable spray drying method was developed and used for the preparation of active, inhalable dry powder formulations of the antimicrobial protein, lactoferrin, and aminoglycosides (tobramycin and gentamicin). The physicochemical properties, aerosolisation performance and the antibacterial properties of the various spray-dried formulations were assessed. In addition, a relevant in vitro cellular model was employed to investigate the potential cytotoxic and pro-inflammatory effects of the various formulations on four bronchial human epithelial cells together with their effectiveness at reducing bacterial colonies when administered on to biofilm co-cultured on the epithelial cells. It was found that following spray drying the particles obtained were mostly spherical, amorphous and possessed suitable aerosolisation characteristics. The various spray-dried antimicrobial proteins (lactoferrin or apo lactoferrin) and co-spray dried combinations of the proteins and aminoglycosides were found to exhibit bactericidal activity against planktonic and biofilms of P. aeruginosa. In general, the spray drying process was found not to significantly affect the antimicrobial activities of the protein. Treatment of the different bronchial epithelial cell lines with the antimicrobial formulations showed that the various formulations were non-toxic and that the co-spray dried combinations significantly reduced established P. aeruginosa biofilms on the four bronchial epithelial cells. Overall, the results from this thesis demonstrates that spray drying could potentially be employed to prepare inhalable antimicrobial agents comprised of proteins and antibiotics. These new combinations of proteins and aminoglycosides has promising applications in the management of P. aeruginosa in the airway of cystic fibrosis patients.
14
Quader, Sabina, and N/A. "Selective Synthetic Modification of Aminoglycosides for Drug Targeting to Tuberculosis." Griffith University. School of Biomolecular and Physical Sciences, 2007. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20071024.151619.
Full textAbstract:
The work presented in this thesis details the synthetic modification of the clinically important aminoglycoside antibiotics, neomycin B, paromomycin and tobramycin. We sought to modify aminoglycosides by attaching lipophilic groups, including fatty acids and steroids, with a view to improving the bacterial membrane permeability of these species, and ultimately their efficacy in the treatment of tuberculosis. Our initial synthetic strategy involved direct and specific functionalization of the singular primary hydroxyl group of the aminoglycoside antibiotic neomycin B, with lipophilic groups containing carboxylic acid functions via Mitsunobu esterification. Although, direct and selective Mitsunobu acylation of the primary hydroxyl group proved unsuccessful in the case of the pseudo tetrasaccharide neomycin B, the Mitsunobu reaction did however result in selective chemistry elsewhere in the molecule and this has been exploited for modification of the ido (ring IV) and streptamine (ring II) ring systems. Under carefully controlled conditions, the Mitsunobu reaction has been used for the selective dehydration of the ido ring, to give the talo epoxide, and, under more forcing Mitsunobu dehydration conditions, an aziridine function has been introduced into the streptamine moiety. Both the epoxide and the epoxide-aziridine neomycin building blocks were utilized as synthons in subsequent chemical transformations. Seventeen novel neomycin derivatives featuring modification of ring IV and/or ring II were obtained using this approach. Explicit structural elucidation of all the synthetic intermediates and the final products was achieved using high temperature NMR spectroscopy. Direct and specific functionalization of the singular primary hydroxyl group at the C5 position of the ribose ring (ring III) of neomycin B was achieved, via a procedure based in part on selective tripsylation of the C5III primary hydroxyl group of neomycin B reported previously, followed by subsequent displacement of the tripsyl group by azide. Terminal alkyne containing lipophilic esters were then successfully attached to the ribose residue of neomycin B via Cu(I)-mediated azide-alkyne coupling reaction. In addition to the isolation of two fortuitous, new and versatile synthons i.e. monoanhydro neomycin and bis-anhydro neomycin for modification of ring IV and ring II of neomycin, a third synthon based on neomycin framework, allowing stepwise modification of ring III and ring IV was designed and synthesized. This synthon features an epoxide function in the ido ring, and a protected amine function at the C5 position of the ribose ring. Examples of the stepwise use of this synthon for further synthetic modification of the neomycin framework were demonstrated. Fourteen novel neomycin derivatives featuring modification of ring III and /or ring IV were obtained and characterized. Regioselective Mitsunobu esterification of the single primary hydroxyl group of the pseudo trisaccharide tobramycin was utilized successfully to link a variety of hydrophobic esters with tobramycin. Nine lipophilic tobramycin derivatives with significant structural diversity were synthesised and characterized. In a preliminary study, the applicability of the Mitsunobu dehydration reaction for the regioselective formation of an epoxide ring in the ido moiety of the pseudo tetrasaccharide aminoglycoside antibiotic paromomycin system was confirmed. The regioselective ring-opening of the derived epoxide with azide at C3IV of paromomycin was also successfully demonstrated. In total, forty-two new potential aminoglycoside antibiotics have been synthesized and characterized.
15
Quader, Sabina. "Selective Synthetic Modification of Aminoglycosides for Drug Targeting to Tuberculosis." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/367086.
Full textAbstract:
The work presented in this thesis details the synthetic modification of the clinically important aminoglycoside antibiotics, neomycin B, paromomycin and tobramycin. We sought to modify aminoglycosides by attaching lipophilic groups, including fatty acids and steroids, with a view to improving the bacterial membrane permeability of these species, and ultimately their efficacy in the treatment of tuberculosis. Our initial synthetic strategy involved direct and specific functionalization of the singular primary hydroxyl group of the aminoglycoside antibiotic neomycin B, with lipophilic groups containing carboxylic acid functions via Mitsunobu esterification. Although, direct and selective Mitsunobu acylation of the primary hydroxyl group proved unsuccessful in the case of the pseudo tetrasaccharide neomycin B, the Mitsunobu reaction did however result in selective chemistry elsewhere in the molecule and this has been exploited for modification of the ido (ring IV) and streptamine (ring II) ring systems. Under carefully controlled conditions, the Mitsunobu reaction has been used for the selective dehydration of the ido ring, to give the talo epoxide, and, under more forcing Mitsunobu dehydration conditions, an aziridine function has been introduced into the streptamine moiety. Both the epoxide and the epoxide-aziridine neomycin building blocks were utilized as synthons in subsequent chemical transformations. Seventeen novel neomycin derivatives featuring modification of ring IV and/or ring II were obtained using this approach. Explicit structural elucidation of all the synthetic intermediates and the final products was achieved using high temperature NMR spectroscopy. Direct and specific functionalization of the singular primary hydroxyl group at the C5 position of the ribose ring (ring III) of neomycin B was achieved, via a procedure based in part on selective tripsylation of the C5III primary hydroxyl group of neomycin B reported previously, followed by subsequent displacement of the tripsyl group by azide.
Terminal alkyne containing lipophilic esters were then successfully attached to the ribose residue of neomycin B via Cu(I)-mediated azide-alkyne coupling reaction. In addition to the isolation of two fortuitous, new and versatile synthons i.e. monoanhydro neomycin and bis-anhydro neomycin for modification of ring IV and ring II of neomycin, a third synthon based on neomycin framework, allowing stepwise modification of ring III and ring IV was designed and synthesized. This synthon features an epoxide function in the ido ring, and a protected amine function at the C5 position of the ribose ring. Examples of the stepwise use of this synthon for further synthetic modification of the neomycin framework were demonstrated. Fourteen novel neomycin derivatives featuring modification of ring III and /or ring IV were obtained and characterized. Regioselective Mitsunobu esterification of the single primary hydroxyl group of the pseudo trisaccharide tobramycin was utilized successfully to link a variety of hydrophobic esters with tobramycin. Nine lipophilic tobramycin derivatives with significant structural diversity were synthesised and characterized. In a preliminary study, the applicability of the Mitsunobu dehydration reaction for the regioselective formation of an epoxide ring in the ido moiety of the pseudo tetrasaccharide aminoglycoside antibiotic paromomycin system was confirmed. The regioselective ring-opening of the derived epoxide with azide at C3IV of paromomycin was also successfully demonstrated. In total, forty-two new potential aminoglycoside antibiotics have been synthesized and characterized.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Faculty of Science, Environment, Engineering and Technology
Full Text
16
Sarwar, Muhammad. "Cloning and expression of aminoglycoside phosphotransferase gene (APH) from a butirosin producing strain of Bacillus circulans." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358607.
Full text
17
Gurnani, Komal. "Molecular basis of the nephrotoxicity of aminoglycoside antibiotics: A Fourier transform infrared spectroscopic investigation." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/6719.
Full textAbstract:
The interaction of gentamicin with daptomycin and PI dispersions was investigated by FTIR spectroscopy. We found no evidence of a direct interaction involving the neutralization of the aspartate residues of daptomycin by gentamicin and the amide I band of daptomycin did not reveal significant conformational changes of its peptidic moiety. On the other hand, daptomycin readily inserts within bilayers of PI, dimyristoylphosphatidylglycerol or dipalmitoylphosphatidylcholine, as judged from its influence on the fluidity of these bilayers. The incorporation of daptomycin into PI bilayers has only a slight effect on the lipopeptide amide I band. The affinity of the aminoglycoside for PI is slightly increased in the presence of daptomycin, in agreement with the results of the dialysis study mentioned above. Gentamicin induces a slight narrowing of the amide I band of daptomycin bound to PI bilayers. The fluidity of the lipid bilayers corresponds to that seen in the absence of both drugs. It is proposed that in the presence of the lipopeptide antibiotic, the critical charge density and membrane fluidity required for optimal enzyme activity is restored, explaining its nephroprotective capabilities. The mechanism of nephroprotection by poly-L-aspartic acid is different from that of daptomycin. Dialysis studies have indicated an optimal binding between gentamicin and polyaspartic acid at acidic pH. We found no evidence of a direct interaction involving the neutralization of the carboxylates of polyaspartic acid by gentamicin and the amide I band of polyaspartic acid did not reveal significant conformational changes. On the other hand, polyaspartic acid had no effect on the spectral features of PI bilayers. A reduction in the changes induced by gentamicin in the lipid head group and interfacial region suggests that the affinity of the aminoglycoside antibiotic decreases in the presence of polyaspartic acid. (Abstract shortened by UMI.)
18
Kumar, Anila. "A study of the effects of the aminoglycoside antibiotics on a human renal cell line." Thesis, University of Sunderland, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302476.
Full text
19
Hunt, Kevan Owen. "An epidemiological study in the greater Durban area of gram negative bacilli resistant to aminoglycoside antibiotics." Thesis, Cape Technikon, 1998. http://hdl.handle.net/20.500.11838/2254.
Full textAbstract:
Thesis (MTech (Medical Technology))--Cape Technikon, 1998.This study was undertaken to investigate resistance to aminoglycoside antibiotics and the transfer of resistance in selected Gram negative bacilli in hospitals in the Greater Durban area in order to determine whether the development of resistance in this region was similar to that found in other countries and whether it was the same in the hospitals in the region. It was intended that the study might expose the existence of nosocomial pathogens of a particular strain or endemic plasmids responsible for aminoglycoside antibiotic resistance. Strains of Klebsiella, Enterobacter and Serratia species and Escherichia coli resistant to gentamicin, tobramycin, netilmicin or amikacin were obtained. Resistance of the isolates obtained to the above aminoglycoside antibiotics was confirmed using a disc diffusion technique. Resistance mechanisms were initially assigned on the basis of resistance to these four aminoglycoside antibiotics. In approximately 50% of the isolates, including donor isolates and their respective transconjugants, resistance mechanisms were confirmed or revised on the basis of a changed resistance profile to a range of 12 aminoglycoside antibiotics in conjunction with DNA/DNA hybridization tests. Bacterial conjugation studies were performed on selected isolates to investigate the transfer of aminoglycoside resistance from Klebsiella pneumoniae isolates to recipient Escherichia coli. Plasmid profiles of all isolates and Escherichia colitransconjugants were compared to establish similarities. Isolates in three of the four genera of bacteria and all isolates collectively, demonstrated the greatest incidence of resistance to tobramycin. Amikacin resistance was, in all groups of isolates, the least frequently encountered. Collectively, the most frequent mechanisms of resistance were the AAC(3)-V and AAC(6')-1 enzymes One large hospital showed a high frequency of the AAC(3)-V modifying enzyme while in other hospitals a wider range of enzyme resistance mechanisms were evident. Plasmid profiles were generally dissimilar within and between different genera and the different hospitals.
Mangosuthu Technikon Research Fund
20
Mehta, Roopal Manoj. "30S Ribosomal Subunit Assembly is a Target for Inhibition by Aminoglycoside Antibiotics in Escherichia coli." [Johnson City, Tenn. : East Tennessee State University], 2002. http://etd-submit.etsu.edu/etd/theses/available/etd-0326102-113130/unrestricted/Mehtat041702.pdf.
Full text
21
Mandhapati, Appi Reddy. "Synthesis of apramycin and paromomycin derivatives as potential next generation aminoglycoside antibiotics and chemistry of isothiocyanato sialyl donors." Thesis, Wayne State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10153408.
Full textAbstract:
AGAs are clinically important antibacterials for human therapy and have long been used as highly potent antibiotics for treating several bacterial infections. The fidelity of protein synthesis is affected by AGAs in the course of binding to specific sites of the bacterial rRNA. The clinical use of AGAs and their applications as therapeutics is restricted by toxicity (irreversible ototoxicity and reversible nephrotoxicity) and by the resistance of pathogens. The objective of this research was the development of proficient AGAs that are less toxic (i.e., more selective) and that evade resistance. The first three chapters of this thesis are aimed towards developing new aminoglycoside antibiotics with the emphasis on their chemical synthesis, and the biological evaluation of newly synthesized analogues, as well as the exploration of structure-activity relationships to understand the mechanism of their antimicrobial activity. In particular, studies have focused on the modification of the aminoglycosides apramycin and paromomycin so as to develop the next generation of potent AGAs.
Chapter two reveals the importance of the 6' and N7' positions of the apramycin by investigation of the antibacterial activity and antiribosomal activity of the ten apramycin derivatives which were synthesized by modifying these locations. The effect of such modifications on antiribosomal activity is discussed in terms of their influence on drug binding to specific residues in the decoding A site. This information is useful in the development of a structure activity relationship for the antibacterial activity of the apramycin class of aminoglycosides and will also assist in the future design and development of more active and less toxic aminoglycoside antibiotics.
Chapter three describes the structure-based design of an improved paromomycin derivative which carries an apramycin-like bicyclic ring I and a conformationally restricted hydroxyl or amine functionality. The influence of the bicyclic paromomycin 6'-hydroxy or amine groups on the binding pattern between AGA and bacterial RNA was investigated by using cell free translational assays. It was found that the bicyclic paromomycin derivative 155 with the equatorial 6’-hydroxy group has a better activity profile than parent paromomycin.
In chapter four, an efficient sialyl donor was developed for the challenging α-sialylation by means of a highly electron withdrawing isothiocyanato group incorporated at C-5 position sialic acid. The isothiocyanato sialyl donor 218 proved to be an excellent α-directing group in sialylation for a wide range of acceptors, and provided high yields. Further, the sialylation of corresponding sialyl phosphate donor 231 was also demonstrated to give excellent selectivity, but yields are lower due to competing elimination. In addition, the rich chemistry of isothiocyanate functionality is explored to introduce a variety of novel functionalities at the 5-position of the sialosides including deamination, an alkyl chain, various amides, and guanidine derivatives.
22
Rayet, Arjinder Kaur. "Analysis of the aminoglycosides neomycin and streptomycin." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/26869.
Full textAbstract:
The aim of the study was the determination of neomycin and streptomycin aminoglycoside antibiotics in bovine kidney tissue at trace levels. The aminoglycosides contain no chromophore making detection difficult by conventional spectrophotometric detection and are highly polar making separation from tissue samples a multistep clean-up procedure.
23
Seward, Rebecca Joanne. "Molecular and epidemiological analysis of antibiotic resistance in Acinetobacter spp." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262787.
Full text
24
Hadipour, Sara. "Purification, characterisation and mutagenesis of aminoglycoside (3')(9) nucleotidyltransferase." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243547.
Full text
25
Kaplan, Elise. "Aminoglycoside modifying enzymes involved in antibiotic resistance : functional and structural studies." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTT006.
Full textAbstract:
L'émergence de bactéries résistantes aux antibiotiques constitue un problème majeur de santé publique responsable d'un nombre croissant de décès, surtout dans les hôpitaux. La résistance aux aminoglycosides est principalement due à l'expression d'enzymes capables de les modifier, comme les aminoglycosides phosphotransférases (APH).Le premier volet de ce travail de thèse vise à mieux comprendre les bases moléculaires des interactions protéine-ligands et de la catalyse enzymatique d'une de ces enzymes, l'APH(2”)-IVa. La spécificité de substrats a été caractérisée en détails pour différents aminoglycosides par des méthodes thermodynamiques, de mesures cinétiques à l'état stationnaire et transitoire, par amarrage moléculaire et cristallographie aux rayons X. La seconde partie de cette étude consiste à développer et optimiser des inhibiteurs allostériques de ces enzymes capables de restaurer l'efficacité des aminoglycosides. Pour cela, une cavité, potentiellement impliquée dans la dynamique de l'APH(2”)-IVa, a été identifiée à partir de simulations de dynamique moléculaire. Celle-ci a servi de cible pour cribler, in silico, 12 000 composés issus de la banque de données Zinc. Ainsi, 14 composés ont été testés in vitro pour leur capacité à diminuer l'activité enzymatique d'APH. Parmi ces derniers, une molécule s'est révélée être un inhibiteur non-compétitif de l'APH(2”)-IVa. Une étude des relations structure-fonction a permis de déterminer les groupements les plus favorables à l'inhibition et d'identifier un composé plus efficace. L'utilisation de ces deux molécules permet de restaurer, par exemple, la sensibilité à la sisomicine d'une souche d'E. faecium exprimant cette enzyme. Cette étude fournit des bases au développement de thérapies combinant un aminoglycoside et un inhibiteur des enzymes d'inactivation constituant une stratégie pour lutter contre la résistance aux antibiotiques dans un contexte thérapeutiqueEmergence of multi-drug resistant bacteria leads to increasing fatal issues especially in hospitals. Resistance to aminoglycoside antibiotics is mainly due to the expression of modifying enzymes, such as aminoglycoside phosphotransferases (APH). The first aim of this project was to elucidate the molecular basis of protein-ligand interactions and catalysis of one of these enzymes, the APH(2”)-IVa. Promiscuity of aminoglycoside substrates has thus been characterized in details using thermodynamics, transient and steady state kinetics, molecular docking and X-ray crystallography techniques.The second part aimed to develop and optimize allosteric inhibitors of these enzymes able to counterbalance aminoglycoside resistance. For this purpose, a small cavity, potentially involved in APH dynamics, was identified from molecular dynamic simulations. This cavity was used as a target to virtually screen 12 000 compounds of the Zinc database. The efficiency of the 14 high-ranked molecules to inhibit APH was evaluated in vitro and lead to the identification of a non-competitive inhibitor of APH(2”)-IVa. Structure-activity relationships highlighted the most favourable substituents for APH inhibition and permitted to obtain a more potent compound. The two molecules were able to restore, for example, sisomicin susceptibility of an E. faecium strain, expressing this enzyme.This study provides a basis for the development of combined chemotherapies (antibiotic with enzyme inhibitor) which may overcome antibiotic resistance in a clinical context
26
Malott, Bradley. "Development and investigation of antibiotic resistance in E. coli using aminoglycosides." Wittenberg University Honors Theses / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wuhonors1617617698561944.
Full text
27
Reva, Anna. "Enzymology of gentamicin biosynthesis." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277902.
Full textAbstract:
Gentamicin C complex is a mixture of five structurally similar aminoglycoside antibiotics, gentamicins C1, C1a, C2, C2a, and C2b, produced by the actinomycete bacterium Micromonospora echinospora. It is established in clinical use and despite significant toxicity remains valuable to treat severe Gram-negative bacterial infections. There is a pressing need to develop novel versions of such antibiotics to combat the rise of resistance among pathogens. Engineering of the pathway requires a detailed knowledge of the genes, enzymes, and intermediates involved. The final steps of gentamicin biosynthesis begin at gentamicin X2, the last common intermediate of the C complex. 6'-C-Methylation generates two branches, with analogous reactions happening in both. Candidate genes and enzymes for the steps from the first 6'-C-methylated intermediate, G418, to an aminated metabolite JI-20B have already been described, but none for the subsequent loss of two hydroxyl groups from Ring II, or the N-methylation that then occurs. A novel separation method using dynamic countercurrent chromatography was successfully applied to the difficult purification of gentamicin metabolites. The results described here allowed a detailed mechanism to be proposed for almost the entire pathway from G418 to the C complex, and by analogy for the unbranched pathway, too. The last step of the pathway is 6'-N-methylation of gentamicins C1a and C2. Genome mining and cell-free assays were used by the group of Professor Yuhui Sun (Wuhan University) to identify genL, a methyltransferase gene encoded elsewhere on the M. echinospora genome and capable of this catalysis. Here, in vitro reactions with recombinant GenL confirmed its function, and its kinetic parameters were measured with its substrates. The full mechanistic pathway for the late stages of gentamicin C complex biosynthesis has therefore now been elucidated.
28
Hon, Wai-Ching. "Crystallographic studies on two structures of a kanamycin kinase : a Mg-AMPPNP and a Mg-ADP complex /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0001/NQ42744.pdf.
Full text
29
Börjesson, Stefan. "Antibiotic Resistance in Wastewater : Methicillin-resistant Staphylococcus aureus (MRSA)and antibiotic resistance genes." Doctoral thesis, Linköpings universitet, Medicinsk mikrobiologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17709.
Full textAbstract:
A large part of the antibiotics consumed ends up in wastewater, and in the wastewater the antibiotics may exert selective pressure for or maintain resistance among microorganisms. Antibiotic resistant bacteria and genes encoding antibiotic resistance are commonly detected in wastewater, often at higher rates and concentrations compared to surface water. Wastewater can also provide favourable conditions for the growth of a diverse bacterial community, which constitutes a basis for the selection and spread of antibiotic resistance. Therefore, wastewater treatment plants have been suggested to play a role in the dissemination and development of antibiotic resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) is a large problem worldwide as a nosocomial pathogen, but knowledge is limited about occurrence in non-clinical environments, such as wastewater, and what role wastewater plays in dissemination and development of MRSA. In this thesis we investigated the occurrence of MRSA in a full-scale wastewater treatment plant (WWTP). We also investigated the concentration of genes encoding resistance to aminoglycosides (aac(6’)-Ie+aph(2’’)), β-lactam antibiotics (mecA) and tetracyclines (tetA and tetB) in three wastewater-associated environments: (1) soil from an overland flow area treating landfill leachates, (2) biofilm from a municipal wastewater treatment plant, and (3) sludge from a hospital wastewater pipeline. In addition, concentrations of mecA, tetA and tetB were investigated over the treatment process in the WWTP. These investigations were performed to determine how the prevalence and concentration of MRSA and the antibiotic resistence genes are affected in wastewater and wastewater treatment processes over time. The occurrence of MRSA was investigated by cultivation and a commercially available real-time PCR assay. In order to determine concentrations of the genes aac(6’)-Ie+aph(2’’), mecA, tetA and tetB in wastewater we developed a LUXTM real-time PCR assay for each gene. Using cultivation and real-time PCR we could for the first time describe the occurrence of MRSA in wastewater and show that it had a stable occurrence over time in a WWTP. MRSA could mainly be detected in the early treatment steps in the WWTP, and the wastewater treatment process reduced the number and diversity of cultivated MRSA. However, our results also indicate that the treatment process selects for strains with more extensive resistance and possibly higher virulence. The isolated wastewater MRSA strains were shown to have a close genetic relationship to clinical isolates, and no specific wastewater lineages could be detected, indicating that they are a reflection of carriage in the community. Taken together, these data indicate that wastewater may be a potential reservoir for MRSA and that MRSA are more prevalent in wastewater than was previously thought. The real-time PCR assays, for aac(6’)-Ie+aph(2’’), mecA, tetA, and tetB that we developed, were shown to be sensitive, fast, and reproducible methods for detection and quantification of these genes in wastewater environments. The highest concentrations of all genes were observed in the hospital pipeline, and the lowest in the overland flow system, with tetA and aac(6´)-Ie+aph(2´´) detected in all three environments. In the full-scale WWTP, we continuously detected mecA, tetA and tetB over the treatment process and over time. In addition, it was shown that the treatment process reduces concentrations of all three genes. The data presented in this thesis also indicate that the reduction for all three genes may be connected to the removal of biomass, and in the reduction of tetA and tetB, sedimentation and precipitation appear to play an important role.
30
Heffernan, Aaron J. "Dose optimisation of intravenous and nebulised antibiotics for the treatment of Pseudomonas aeruginosa pneumonia." Thesis, Griffith University, 2023. http://hdl.handle.net/10072/421611.
Full textAbstract:
Ventilator-associated pneumonia remains commonplace in critically ill patients and is associated with an increased morbidity and mortality. Multidrug-resistant Gram-negative bacillary pathogens, such as Pseudomonas aeruginosa, are commonly implicated in the pathogenesis of ventilator-associated pneumonia. Increasing rates of antibiotic resistance have led to increasing interest in repurposing old antibiotics with alternative administration methods and the development of new antibiotics that have activity against these multidrug-resistant isolates. Moreover, ensuring that the optimal dose is used is of paramount importance to improve patient outcomes and prevent resistance emergence to these novel antibiotic therapies.
Amikacin, an aminoglycoside antibiotic, is of interest in the management of ventilator-associated pneumonia given that it retains activity in up to 70% of multi-drug resistant P. aeruginosa isolates. However, amikacin penetrates poorly into the infection site in patients with ventilator-associated pneumonia, resulting in subtherapeutic exposures when administered intravenously. Therefore, there has been renewed interest in dosing for innovative administration methods, such as inhaled dosing for direct drug delivery to the site of infection. Alternatively, new agents such as ceftolozane/tazobactam, have been developed and are increasingly used clinically, particularly for multidrug-resistant P. aeruginosa. However, a paucity of pharmacodynamic studies exist to assist clinicians with prescribing a dose that both increases the probability of treatment success and minimises the emergence of resistance.
Therefore, the primary aims of this thesis are to describe the infection site pharmacodynamics of amikacin and ceftolozane/tazobactam against P. aeruginosa, to determine the likely dosing strategies for both agents that will achieve maximal bacterial killing and minimise the risk of resistance emerging. A series of in vitro studies and in silico simulations are used to describe the impact of different dosing regimens on bacterial killing and emergence of resistance.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Medicine & Dentistry
Griffith Health
Full Text
31
Becker, Matthias. "LC-MS/MS-Methoden zur Rückstandsanalyse von Penicillinen, Cephalosporinen und Aminoglycosid-Antibiotika." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974085324.
Full text
32
Millar, Kristina K. "Antibiotic Efficacy and Interaction in Escherichia coli during Varying Nutrient Conditions." Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/scripps_theses/809.
Full textAbstract:
Due to the recent rise in antibiotic resistant pathogens, and the difficulties surrounding the quest for new antibiotics, many researchers have started revisiting antibiotic interactions in hopes of finding new treatment options. The primary outcome of this project was to examine the efficacy of concomitant antibiotic use under varying nutrient conditions, to identify variations in antibiotic interactions. Antibiotic interactions were studied, utilizing E. coli as a model bacterial system, grown in four different media types. E. coli cultures were treated with streptomycin, tobramycin, erythromycin, and amikacin individually and in a pairwise fashion at varying doses. We found that at least some antibiotic efficacies were dependent on the environmental nutrient conditions E. coli was grown in, as the antibiotics were not equally effective in all media types. E. coli grown in potato dextrose broth, in particular, showed extremely high tolerance to antibiotic inhibition. In addition, we observed several variations in antibiotic interactions, depending on the combination of antibiotics and environmental conditions utilized. It is predicted that differences in available nutrients is the primary cause of the observed discrepancies in antibiotic properties between media. The observation of changes in antibiotic efficacy under different environmental and nutrient conditions has serious implications for use of antibiotic combinations as drug treatments. Not all microenvironments within the human body have identical nutrient make-up. If the interactions antibiotics are reported to have in one environmental condition change under another, reckless prescription of combinations could lead to a serious adverse reaction. Thus, this is an important area for future in vitro and in vivo research.
33
Petri, Serrano César. "Transformación genética del albaricoquero (Prunus armeniaca L.), mediada por Agrobacterium, y regeneración de plantas transformadas." Doctoral thesis, Universidad de Murcia, 2005. http://hdl.handle.net/10803/10727.
Full textAbstract:
ResumenEn esta tesis se ha optimizado un protocolo de regeneración a partir de material varietal de 'Helena' y 'Canino'. Mediante el estudio de los diversos factores que afectan la transformación de material adulto, se ha establecido por primera vez un protocolo eficiente de transformación mediada por Agrobacterium tumefaciens de una variedad comercial de albaricoquero.El diseño de una estrategia de selección gradual con paromomicina ha permitido la regeneración de plántulas transformadas con los genes marcadores nptII y sgfp o gus, con las eficiencias más elevadas que se han publicado hasta el momento para transformar material varietal en especies del género Prunus, aunque la baja viabilidad de las yemas transformadas redujo el número final de plantas obtenidas.El protocolo establecido en esta tesis sienta las bases que permitirán la introducción de genes de interés agronómico y comercial, modificando de manera discreta variedades élite aceptadas y establecidas en el mercado.In this thesis a protocol of regeneration has been optimized from leaf explants of the cultivars 'Helena' and 'Canino'. By means of the study of the diverse factors that affect the transformation of adult material, an efficient protocol of Agrobacterium tumefaciens-mediated transformation has been established for the first time for a commercial cultivar of apricot.The design of a gradual selection strategy with paromomycin has permitted the regeneration of transformed shoots with the marker genes nptII and sgfp or gus, with the highest efficiencies that have been published up to now from adult material in Prunus, although the low viability of the transformed buds reduced the final number of plants obtained. This protocol establishes the bases that will permit the introduction of agronomic and commercial interesting genes, modifying discreetly commercial cultivars accepted and established in the market.
34
Bossaer, John B., and Paul O. Lewis. "Antibiotic Use in Home Health: A Primer." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/2316.
Full textAbstract:
Cost containment measures within hospital systems push for earlier discharges on stable patients. Due to patient placement difficulties and costs associated with skilled facilities, antibiotic use in home health care settings is becoming a common occurrence. This trend will likely increase as care continues to shift to outpatient areas. Lack of sufficient serum drug concentrations needed in severe infections and increasing resistance to many of the oral options often necessitates the use of the intravenous (IV) route. Home health care practitioners may have minimal information on patients or limited experience with IV antibiotics that may impact quality of care. This review summarizes key points relevant to IV antibiotics routinely used by home health prescribers, nurses, technicians, and care managers. This review will focus on antibacterial agents including vancomycin, aminoglycosides, beta-lactams, daptomycin, tigecycline, and telavancin. Appropriate dosing, indications, adverse events, monitoring parameters, and feasibility of using IV antibiotics are discussed.
35
Chen, Yang. "Structural and Biochemical Studies of Antibiotic Resistance and Ribosomal Frameshifting." Doctoral thesis, Uppsala universitet, Institutionen för cell- och molekylärbiologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205131.
Full textAbstract:
Protein synthesis, translation, performed by the ribosome, is a fundamental process of life and one of the main targets of antibacterial drugs. This thesis provides structural and biochemical understanding of three aspects of bacterial translation. Elongation factor G (EF-G) is the target for the antibiotic fusidic acid (FA). FA binds to EF-G only on the ribosome after GTP hydrolysis and prevents EF-G dissociation from the ribosome. Point mutations in EF-G can lead to FA resistance but are often accompanied by a fitness cost in terms of slower growth of the bacteria. Secondary mutations can compensate for this fitness cost while resistance is maintained. Here we present the crystal structure of the clinical FA drug target, Staphylococcus aureus EF-G, together with the mapping and analysis of all known FA-resistance mutations in EF-G. We also present crystal structures of the FA-resistant mutant F88L, the FA-hypersensitive mutant M16I and the FA-resistant but fitness-compensated double mutant F88L/M16I. Analysis of mutant structures together with biochemical data allowed us to propose that fitness loss and compensation are caused by effects on the conformational dynamics of EF-G on the ribosome. Aminoglycosides are another group of antibiotics that target the decoding region of the 30S ribosomal subunit. Resistance to aminoglycosides can be acquired by inactivation of the drugs via enzymatic modification. Here, we present the first crystal structure an aminoglycoside 3’’ adenyltransferase, AadA from Salmonella enterica. AadA displays two domains and unlike related structures most likely functions as a monomer. Frameshifts are deviations the standard three-base reading frame of translation. -1 frameshifting can be caused by normal tRNASer3 at GCA alanine codons and tRNAThr3 at CCA/CCG proline codons. This process has been proposed to involve doublet decoding using non-standard codon-anticodon interactions. In our study, we showed by equilibrium binding that these tRNAs bind with low micromolar Kd to the frameshift codons. Our results support the doublet-decoding model and show that non-standard anticodon loop structures need to be adopted for the frameshifts to happen. These findings provide new insights in antibiotic resistance and reading-frame maintenance and will contribute to a better understanding of the translation elongation process.
36
Findlay, Brandon. "Design and synthesis of cationic amphiphiles." American Society for Microbiology, 2010. http://hdl.handle.net/1993/21708.
Full textAbstract:
Cationic antimicrobial peptides (CAMPs) are produced by plants, animals and bacteria to protect their host against antagonistic microbes. The antitheses of selective antibiotics, these peptides are drawn by electrostatic and hydrophobic interactions to targets as diverse as the bacterial membrane, nucleic acids and serum proteins. This lack of specificity is their greatest strength, as mutations to single genes rarely lead to bacterial resistance. Resistance may be conferred by large scale alterations in cell envelope composition, which generally reduces bacterial fitness in the absence of peptide.
Clinical applications of natural CAMPs are limited, as the peptides are toxic to mammalian cells and rapidly inactivated in vivo by serum albumin and proteases. Faced with these challenges we have prepared a number of CAMP analogues, with the goal of creating lead compounds for further development of antibacterial therapeutics. Much of our work has focused on ultrashort lipopeptides and lipopeptoids, which have properties similar to natural CAMPs and extremely abbreviated sequences. The simple structure of these scaffolds allows rapid creation of CAMP analogues in a brief period of time, allowing us to rapidly explore the structural requirements for CAMP activity. The balance of this work focuses on imparting CAMP-like behaviour to known antibiotics, in order to expand their spectrum of susceptible bacteria and combat the development of drug-resistant bacteria. In particular, the aminoglycosides neomycin and tobramycin have been fused to phenolic disinfectants such as triclosan and biclotymol, in order to improve their diffusion across the bacterial envelope and activity against Gram-negative bacteria.
37
Sabeti, Azad Mahnaz. "Accumulation of a bactericidal antibiotic by tolerant bacteria and insights into bacterial persistence." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS585.
Full textAbstract:
Les aminoglycosides (AG) sont une famille d’antibiotiques qui ciblent le ribosome bactérien. À titre d’exemple il s’agit de la néomycine, la gentamicine et la streptomycine. Quand ces antibiotiques se fixent au ribosome, ils provoquent des erreurs de lectures ou inhibent la synthèse des protéines, ce qui conduit à la mort cellulaire. Même s’ils ont été découverts il y a plus d’un demi-siècle, de nombreux aspects de leur mode d’action restent inconnus. L’accumulation des AG dans les bactéries se passe en trois étapes. La première consiste en une interaction électrostatique avec la membrane. La deuxième est une phase I énergie-dépendante (EDPI). Les antibiotiques rentrent dans le cytoplasme, atteignent les ribosomes, ce qui cause des erreurs de lecture et donc la production de protéines mal repliées. EDPI dépend du niveau énergétique de la cellule et le mécanisme d’entrée à travers les membranes reste inconnu. La troisième étape est la deuxième phase énergie-dépendante (EDPII), où l’antibiotique pénètre dans le cytoplasme en grande quantité par des membranes endommagées lors de la phase I. Le but de cette thèse était de créer de nouveaux outils afin d’étudier l’interaction des AG avec les bactéries et d’appliquer la méthodologie à des bactéries en phase rapide de croissance ou bien en état de persistance. Nous avons synthétisé des conjugués fluorescents des AG aux propriétés bactéricides. Avec ces conjugués nous avons analysé l’interaction des AG avec les bactéries à l’échelle de la cellule unique par microscopie de fluorescence. Nous avons combiné cette technique avec la cytométrie de flux (FACS) pour évaluer la cinétique d’accumulation. Cette étude démontre qu’il y a deux types d’accumulation : une à la périphérie avec interaction à la membrane et une deuxième où l’antibiotique est localisé dans le cytoplasme. Notre analyse démontre aussi que de faibles niveaux d’antibiotiques dans le cytoplasme sont tolérés et n’inhibent pas la croissance cellulaire. En utilisant un inhibiteur des phases EDPI et EDPII nous démontrons que cette technique permet de distinguer les différentes étapes de l’accumulation. Au cours d’ajustements du protocole, nous avons découvert que les AG peuvent entrer dans le cytoplasme par mechano-sensation et activation de canaux mécanosensibles (MS). Ces canaux sont connus pour avoir une affinité pour les AG. Ici pour la première fois nous montrons qu’une manipulation mécanique ouvre les canaux et stimule une entrée massive d’antibiotiques. Ce résultat inattendu pourrait permettre de mieux comprendre le mécanisme d’entrée des AG dans le cytoplasme. Après avoir étudié l’accumulation des AG dans les cellules en croissance nous avons étudié la tolérance aux AG pour les bactéries en phase de dormance : les cellules persistantes. Elles forment une sous-population parmi une population sensible. Elles sont en dormance et tolèrent de fortes doses d’antibiotiques. En absence d’antibiotique elles sortent de l’état de dormance pour reformer une population sensible à l’antibiotique. Par microscopie de fluorescence, nous montrons que les cellules persistantes ont une accumulation périphérique d’AG. Grâce à notre méthodologie, nous avons un outil performant pour identifier les différents états d’accumulation des AG. Avant cette étude il était seulement possible de connaître les niveaux d’accumulation mais la localisation de l’antibiotique demeurait inaccessible. Nous avons avec cette méthode étudié deux mutants d’E. coli, qui sont moins tolérants aux AG et identifié leurs caractéristiques d’accumulation. Enfin, nous avons développé un système de microfluidique adapté à l’étude de nos conjugués fluorescents pour étudier en temps réel l’accumulation par les cellules persistantesAminoglycoside (AG) is a family of antibiotic which target bacterial ribosome. Few examples of this family are neomycin, gentamicin and streptomycin. When these antibiotics bind to ribosomes, they cause miscoding or inhibit protein synthesis which consequently leads to cell death. Although discovery of these antibiotics was more than half a century ago, there are many facts about AGs’ action mechanism which remain unknown. AG accumulation in the bacterial cells happens in three steps. First step is cell membrane attachment. This step is driven by an electrostatic interaction with the cationic AGs. Second step is an energy dependent phase I (EDPI). In EDPI, the antibiotic enters into the cytoplasm and reaches ribosomes, causing miscoding and production of misfolded proteins. EDPI depends on cellular energy level, however to date the mechanism by which AGs pass through membranes and enter cytoplasm is unknown. The third step is energy dependent phase II (EDPII) in which the antibiotic enters into the cytoplasm in larger amount due to damages in the membrane that resulted from EDPI. The aim of this PhD was to create new tools to study the interaction of AGs with bacteria and apply the methodology to study fast growing bacteria as well as persister cells. We have made fluorescently-tagged AGs with preserved bactericidal properties. We used these conjugates to track down the interaction of AG at single cell level by fluorescence microscopy. We combined fluorescence microscopy and fluorescence-activated cell sorting (FACS) analysis to measure AGs accumulation in the cells at different time points to capture the kinetics of antibiotic penetration. This study showed that there are two accumulations patterns for the drug in cells: in the first step there is a peripheral accumulation, which corresponds to specific binging to cell membrane. Next there is a cytoplasmic accumulation in which the antibiotic in entering into the cytoplasm. According to microscopy time laps study, low levels of cytoplasmic accumulation is tolerated by cells and did not cause cell death. Using FACS analysis, we used an inhibitor of EDPI and EDPII and proved that with this technique we can distinguish different steps of AGs accumulation. During protocol adjustment steps we found that AGs can enter into the cytoplasm as a result of mechanosensation and activation of mechanosensitive (MS) channels. These channels have already been shown to have affinity to AG and here this is a first time that we observed that mechanical manipulation of cells lead to opening of MS channel causing massive cytoplasmic accumulation. This unpredictable result may lead us to a better understanding of the mechanism of AG entrance into the cytoplasm. After studying AG accumulation in fast growing cells, we studied AG tolerance for non-growing cells, which are called persisters. Persisters are antibiotic tolerant sub-population among susceptible bacterial cell population. Persisters are non-growing, dormant cells which tolerate high concentrations of antibiotic. In the absence of antibiotic, they exit this dormant state and grow into an antibiotic susceptible population. By fluorescence microscopy we showed that persister cells have peripheral accumulation of AG. Thanks to our methodology, we have a powerful tool by which we can determine the patterns of AG accumulation. Prior to this study, it was only possible to know the levels of accumulation and not the corresponding patterns. We applied the method to investigate AG accumulation in two mutants of E. coli, which are less tolerant to AG and defined their pattern of accumulation. Finally, we developed a coated microfluidic system, which is adapted to our antibiotics for studying in real time drug accumulation by persister cells
38
Obszynski, Julie. "Conception et synthèse d'aminoglycosides guidées par l'ARN." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF018.
Full textAbstract:
Le développement de nouveaux antibiotiques est un enjeu majeur de santé publique. Etant donné, le fort potentiel des aminoglycosides en tant qu’antibiotique, ces composés ont attisé l’intérêt de plusieurs groupes de recherche. Cependant, leur usage est encore très limité, malgré leur ancienneté, du fait de leur toxicité et du développement toujours croissant des mécanismes de résistances aux aminoglycosides. Afin de mieux appréhender les problèmes inhérents à leur utilisation, il est crucial de mieux comprendre leur action sur les différentes cibles cellulaires, et d’étudier leur interaction avec leur cible moléculaire (ARN et protéine). En plus de leur pouvoir antibiotique, les aminoglycosides sont également des ligands universels pour des ARN, capables d’interagir spécifiquement avec notamment les ARN du VIH-1 suivants : DIS, TAR, RRE. L’élaboration d’aminoglycosides modifiés présente un énorme avantage car le domaine d’application, et en conséquence les retombées, sont grandes. Néanmoins, la complexité structurale de ces molécules est un frein majeur, la fonctionnalisation chimiosélective est indispensable mais malheureusement peu décrite dans la littérature. Dans le cadre de ce travail, nous avons développé deux types d’approches pour cibler le DIS et/ou le site A du ribosome bactérien. La première originale, mais risquée se base sur le concept de click in situ. La seconde approche est traditionnelle et est basée sur la fonctionnalisation sélective de certaines positions clés des aminoglycosidesThe development of new antibiotics is a major public health issue. Given the high potential of aminoglycosides as antibiotics, these compounds have aroused great interest in many research groups. However, despite their maturity, their use is still limited because of their toxicity and the increasing development of resistance mechanisms to aminoglycosides. To better understand the problems inherent to their use, it is crucial to understand their action a cellular level, and to study the interactions with their molecular targets (RNA and protein). In addition to their antibiotic power, aminoglycosides are also universal ligands for several RNAs, capable of specific interactions with RNAs of HIV-1: DIS, TAR and RRE. The elaboration of modified aminoglycosides presents a huge advantage because the domain of application, and therefore the benefits, are important. Nevertheless, the structural complexity of these molecules is a major constraint, chemoselective functionalization is essential but unfortunately poorly described in the literature.In this work, we developed two approaches to target the DIS and/or the A site of the bacterialribosome. The first one, unique but challenging is based on the concept of in situ click chemistry. The second approach is conventional and is based on the selective functionalization of some keypositions of aminoglycosides
39
Frazier, Ashley Denise. "An Investigation of Bacterial Ribonucleases as an Antibiotic Target." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etd/1417.
Full textAbstract:
Antibiotics have been commonly used in medical practice for over 40 years. However, the misuse and overuse of current antibiotics is thought to be the primary cause for the increase in antibiotic resistance.
Many current antibiotics target the bacterial ribosome. Antibiotics such as aminoglycosides and macrolides specifically target the 30S or 50S subunits to inhibit bacterial growth. During the assembly of the bacterial ribosome, ribosomal RNA of the 30S and 50S ribosomal subunits is processed by bacterial ribonucleases (RNases). RNases are also involved in the degradation and turnover of this RNA during times of stress, such as the presence of an antibiotic. This makes ribonucleases a potential target for novel antibiotics.
It was shown that Escherichia coli mutants that were deficient for RNase III, RNase E, RNase R, RNase G, or RNase PH had an increase in ribosomal subunit assembly defects. These mutant bacterial cells also displayed an increased sensitivity to neomycin and paromomycin antibiotics. My research has also shown that an inhibitor of RNases, vanadyl ribonucleoside complex, potentiated the effects of an aminoglycoside and a macrolide antibiotic in wild type Escherichia coli, methicillin sensitive Staphylococcus aureus, and methicillin resistant Staphylococcus aureus.
RNases are essential enzymes in both rRNA maturation and degradation. Based on this and previous work, the inhibition of specific RNases leads to an increased sensitivity to antibiotics. This work demonstrates that the inhibition of RNases might be a new target to combat antibiotic resistance.
40
O'Reilly, Molly. "Prevention of aminoglycoside antibiotic-induced ototoxicity of auditory hair cells via block of mechano-electrical transducer channels or intracellular mechanisms." Thesis, University of Sussex, 2019. http://sro.sussex.ac.uk/id/eprint/81606/.
Full textAbstract:
This thesis addresses the pressing concern of clinical drug-induced hearing loss (ototoxicity). Described herein is the mechanism by which ototoxicity emerges following drug administration both in a clinical setting and in an in vitro model assay system used for its investigation, through use of mouse cochlear cultures. The predominant nature of this research concerns the identification of novel otoprotectants - compounds that when co-administered alongside clinical drug treatments can prevent the unfortunate ototoxic side-effect from occurring. Here I present my research, focussing on the identification of a number of novel compounds that have the potential to be taken forward to in vivo screening and, ultimately, clinical trials. Moreover, for each identified compound I present my investigation of their mechanism of protection - which could arise either by preventing the entry of the ototoxicity-inducing drugs into the sensory hair cells of the inner ear, or prevent their induction of apoptosis once inside the cell. To investigate their protective mechanism I employed a variety of methods, including: electrophysiology, fluorescent imaging and mitochondrial respirometry. Conclusively, I have identified at least five novel otoprotectants with the potential for clinical use. I show that three of these compounds likely block the entry of the damaging drugs into sensory hair cells, whereas the remaining two are thought to work intracellularly. Moreover, the two most effective compounds that I have identified seemingly work intracellularly, suggesting this to be the most viable mechanism of otoprotection for further investigation. I also show the potential for compound modification based on their mechanism of protection as a way of improving a compound's otoprotective profile. Lastly, I devised an assay for the screening of clinical drug effects on mitochondria and employ this as a new avenue of screening for otoprotection.
41
Obwana, Balusaba-Arum. "Synergistic activities of the selected antibiotics of fluoroquinolones, β-lactams, aminoglycosides, glycopeptides and streptogramins against gentamicin-resistant Enterococcus faecalis and Enterococcus faecium." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/25035.
Full textAbstract:
The aim of this study was to investigate synergistic activities of the combined antibiotics against the gentamicin resistant Enterococcus faecalis and Enterococcus faecium and to establish the existence of some genes involved in the resistance of enterococci against gentamicin and ciprofloxacin. The total of 81 clinical isolates were collected for the study and all were found to be resistant to gentamicin (MICs range 32->256mg/l). 50 isolates were found to be resistant to ciprofloxacin with MICs range 64->256mg/l. The synergistic activities of the antibiotics combinations were establish against E. faecalis and E. faecium Clinical isolates. The combination between Amoxicillin and gentamicin against E. faecalis resulted into synergy with MIC at 90% of 0.5mg/l and for E. faecium, MIC at 90% was 2mg/l. Vancomycin and gentamicin combination had MIC at 90% of 2 mg/l for E. faecalis and 1mg/1 for E. faecium. Teicoplanin and synercid combination showed synergistic activity of MIC at 90% of 0.5mg/l for E. faecalis while E. faecium had also 0.5mg/l. The combination between teicoplanin and ciprofloxacin had synergy with MIC at 90% of <0.25mg/l for E. faecalis and E. faecium had the same activity of MIC at 90% of <0.25mg/l. The combination between amoxicillin and synercid resulted into synergistic activity at MIC 90% of 4mg/l for E. faecalis and also 4mg/l for E. faecium. The antagonistic activity was observed between combination of vancomycin and synercid with MIC at 90% of 32mg/ for E. faecalis and MIC at 90% of 16mg/l for E. faecium. The combination between Synercid and ciprofloxacin resulted into synergistic activity at 90% MIC of 4mg/l for E. faecium. The checkerboard test of the combination between synercid and ciprofloxacin against four clinical isolates of E. faecium resulted into FIC indices of 0.4 for isolate D002 and 0.4 for isolate G051. While isolate 788/5/95 had 0.3 and NCTC12202 had also 0.3. These indices confirm the synergistic activity of the combined antibiotic of the two drugs. Of 27 isolates tested for the presence of aminoglycoside modifying enzymes using PCR technique, only 8 (2 E. faecium and 6 E. faecalis) showed the positive results of the presence of AME. However, the presence of the AME did not prevent the synergistic activities of the combined drugs against E. faecalis and E. faecium. The PFGE study showed the heterogeneous existence of these gentamicin resistance isolates from RIE.
42
Zhang, Jianjun. "Library Synthesis of Anticancer and Antibacterial Agents via Azide Chemistry." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/711.
Full textAbstract:
Various anticancer and antibacterial agents have been synthesized via azide chemistry by taking advantage of carbohydrate. Starting from the synthesis of 14 glycosyl azides, a library of carbohydrate-oxazolidinone conjugates and a library of carbohydrate-cyclopamine conjugates with biological interests were synthesized based on a highly efficient "click reaction" assisted by sonication. Some of the conjugates have improved solubility and enhanced anticancer activity. A library of neomycin B derivatives with various modifications at the 5" position has been synthesized. Two leads exhibit prominent activity against both methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Antibacterial activities were measured when combined with other clinically used antibiotics and significant synergistic activities were observed. Three different classes of aryl N-glycosides have been synthesized by employing 1,4-naphthoquinone and glycosyl azides undergoing a [2+3] cycloaddition. Alkyl azides can also undergo the same cycloaddition. After the removal of the protecting group, a library of 9,10-anthraquinone derivatives with potential anticancer activity and a library of 2-aminomethylene-1,3-indanediones with novel antibacterial activity have been developed, respectively. A one-pot three-component [2+3] cycloaddition for the synthesis of 1-alkyl 1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione and 2-alkyl 2H-naphtho[2,3-d][1,2,3] triazole-4,9-dione has been developed. By taking the advantage of their difference in basicity, both products can be obtained in good purity. Using an allylic azide rearrangement, a convenient method has been developed for the synthesis of several 2',3'-dideoxyaminoglycosides. The antibacterial activity of these novel aminoglycosides also confirms the indispensable role of the 2'-NH2 group for both neomycin and kanamycin classes of aminoglycosides. A novel structural motif containing the hexylaminocarbonyl groups at O-5 and/or O-6 of 2',3'-dideoxyneamine could lead to the production of new aminoglycosides against resistant bacteria.
43
Boyer, Alexandre. "Maîtrise de la résistance bactérienne : réflexions sur la phase empirique de l'antibiothérapie en réanimation." Thesis, Bordeaux 2, 2012. http://www.theses.fr/2012BOR21926/document.
Full textAbstract:
En réanimation, les facteurs de risque d’infection à bactéries résistantes sont nombreux et il est nécessaire d’instaurer une antibiothérapie rapide et adéquate. Cela conduit donc souvent au choix empirique d’antibiotiques à large spectre. Ce travail de thèse regroupant quatre études porte sur les éléments de ce choix. Dans la première étude, les critères de "pneumopathie associée aux soins" sont discutés. Dans la seconde, il est rapporté que le traitement antibiotique prescrit au début du séjour en réanimation est associé à l’acquisition de Pseudomonas aeruginosa. Dans le diagnostic d’une pneumopathie acquise sous ventilation, la troisième étude décrit une technique rapide d’antibiogramme permettant une désescalade antibiotique plus précoce. La néphrotoxicité des aminoglycosides dans le traitement empirique des patients en sepsis sévère est présentée dans la dernière étude. Ces travaux participent à la bonne gestion des antibiotiques à la phase empirique du traitement des infections sévères en réanimationIntensive care units (ICU) are a niche for risk factors of infection due to multidrug resistant bacteria. ICU patients are in a need for a rapid and adequate antibiotic therapy. This leads ICU physicians to use empirical broad spectrum antibiotics. This thesis comprises four studies which focus on the empirical step of the treatment. In the first study, the criteria for "health-care-associated pneumonia" are discussed. The second shows that the antibiotic selection pressure administered early during the ICU stay could lead to Pseudomonas aeruginosa acquisition. In the third study, a rapid direct specimen testing method was assessed for ventilator-associated pneumonia diagnosis in order to hasten antibiotic de-escalation. Finally, a review on aminoglycosides’ nephrotoxicity in the severe sepsis setting represents the fourth study. These studies bring a loop forward into the understanding of the antibiotic stewardship of patients with severe sepsis, with particular focus on the empirical antibiotic treatment
44
Hjerdt-Goscinski, Gunilla. "Antibiotic-induced Bacterial Toxin Release – Inhibition by Protein Synthesis Inhibitors." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4692.
Full text
45
Pradier, Léa. "Une approche éco-évolutive de la propagation de la résistance antibiotique : l'exemple de la résistance aux aminoglycosides." Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONG014.
Full textAbstract:
Face à la pression des antibiotiques de nombreux mécanismes de résistances existent. Ces derniers représentent un problème de santé publique qui a et va avoir des conséquences importantes sur la mortalité humaine. Malgré diverses stratégies — principalement basées sur la réduction de la consommation d'antibiotiques — ce problème persistant peine à être contenu. De plus, même s'il est indéniable que l'utilisation massive d'antibiotiques au cours des dernières décennies a été un moteur de l'évolution de la résistance aux antibiotiques, son impact sur l'émergence et la propagation de la résistance aux antibiotiques est souvent surestimé par rapport à d'autres facteurs. Premièrement, la sélection sur la résistance aux antibiotiques ne peut pas être limitée aux antibiotiques à usage humain. Deuxièmement, l'évolution (c'est-à-dire l'émergence, le maintien et la diffusion) d'un trait dans une population repose également sur d'autres forces évolutives et processus écologiques. Enfin, l'entrelacement de ces facteurs résulte en une évolution complexe du phénotype résistant, dépendante de plusieurs échelles allant du déterminisme génétique aux dynamiques environnementales. L'objectif de cette thèse est donc, en s'appuyant sur une approche éco-évolutive, d'améliorer la compréhension des forces et des mécanismes qui façonnent les directions et le mouvement des gènes de résistance aux antibiotiques. Pour ce faire, cette thèse se concentre sur la résistance aux aminoglycosides par le biais d'enzymes d'altération. Les résultats de ces travaux mettent en évidence l'importance des facteurs écologiques et génomiques dans la circulation des gènes de résistance, et concluent ainsi à la nécessité d'études intégratives de la résistance. Dans un premier temps, cette thèse révèle que la distribution de la résistance aux aminoglycosides n'est que très peu liée aux variations de consommation d'aminoglycosides en Europe, mais fortement structurée par la mondialisation (commerce, migration) et plus encore par la connectivité écologique. Une analyse ultérieure souligne le rôle sous-estimé des bactéries non pathogènes dans le transfert horizontal des gènes de résistance aux antibiotiques à grande échelle phylogénétique. A la lumière de ces résultats, cette thèse propose des pistes de réflexion sur l'étude et la gestion des résistances aux antibiotiquesIn front of the antibiotic pressure, a wide range of resistance mechanisms exist. They represent an increasing public health issue, which does and will have major consequences on human mortality. Current strategies —mostly based on antibiotic consumption reductions— globally fail to contain this persistent issue. Moreover, even though it is undeniable that the extensive antibiotic use during the past decades has been a driver of antibiotic resistance evolution, its impact on the emergence and the propagation of antibiotic resistance is often overestimated compared to other factors. First, selection on antibiotic resistance cannot be restricted to the medical and veterinary uses of antibiotics. Second, the evolution (i.e. the emergence, maintenance and spread) of a trait in populations also relies on other evolutionary forces and ecological processes. Finally, the intertwining of these factors induces an intricate evolution of resistant phenotypes, relying on several scales ranging from genetic determinism to environmental dynamics. The aim of this thesis is therefore, through an eco-evolutionary approach, to improve the understanding of forces and mechanisms shaping directions and movements of antibiotic resistance genes. To do so, this thesis focuses on aminoglycoside resistance by modifying enzymes. The results of this work highlight the importance of ecological and genomic factors in the circulation of resistance genes, and thus conclude that integrative studies of resistance are thus required. To begin with, this thesis reveals that the distribution of aminoglycoside resistance is loosely linked to variation in aminoglycoside consumption across Europe, but strongly structured by globalization (trade, migration) and even more by ecological connectivity. Subsequent analysis underscores the underestimated role of non-pathogenic bacteria in the horizontal transfer of antibiotic resistance genes at large phylogenetic scales. In the light of these results, this thesis opens up a course of reflection on the study and management of antibiotic resistance
46
Morais, Pedro Alves Bezerra. "Síntese e atividade biológica da 2-desoxiestreptamina." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/60/60138/tde-02122008-165131/.
Full textAbstract:
Os antibióticos aminoglicosídeos adquiriram uma posição relevante no cenário terapêutico devido ao interesse na regulação da síntese protéica bacteriana em nível de RNA, uma vez que são ligantes inespecíficos para diversos tipos de RNA bacterianos, como RNA mensageiro, RNA transportador e RNA ribossômico. Esta classe de antibióticos apresenta amplo espectro de ação, particularmente contra bactérias Gram-negativas. Recente abordagem estende o uso dos antibióticos aminoglicosídeos como agentes antivirais devido a sua afinidade de ligação ao RRE-, Rev Responsive Element, e TAR-, Trans-Acting Responsive sequence HIV RNA. Por conseguinte, há uma inibição competitiva envolvendo seus correspondentes ligantes naturais, as proteínas Rev e Tat, interrompendo a replicação, do vírus HIV-tipo 1. Em virtude da importância de derivados simplificados dos antibióticos aminoglicosídeos na busca por derivados vestíbulo-tóxico seletivos ou RNA-ligantes, o presente trabalho propõe a síntese do amino- e carba-açúcar 2-desoxiestreptamina, 16, a qual apresenta um desafio sintético interessante devido à presença de cinco centros estereogênicos contínuos com substituintes em relação trans no anel e pode ser utilizada na construção de moléculas mais complexas A estratégia sintética proposta para preparação do composto meso 2-desoxiestreptamina (16), envolve metodologia inédita e foi desenvolvida em duas rotas sintéticas: (i) preparação do carba-açúcar precursor 46 e (ii) preparação de 16 propriamente dito.Aminoglycoside antibiotics received a relevant position in the therapeutic scenario due to the interest in the regulation of bacterial protein synthesis at the RNA-level, since they are a unspecific ligands to several bacterials RNA types, such as mRNA, tRNA and rRNA. These types of antibiotics show a broad spectrum of activity, particulary against gram negative bacteria. New approach extends the use of aminoglycosides as antiviral agents owing to their binding affinity to RRE- Rev Responsive Element and TAR- Trans-Acting Responsive sequence of HIV RNA. Thus, there is a competitive inhibition involving their corresponding natural ligands Rev and Tat proteins, disrupting the HIV-1 virus replication. Regarding the importance of simplified aminoglycoside antibiotics in the search for selective vestibule-toxic derivatives or RNA-ligands, this work focuses on the synthesis of the amino- and carba-sugar 2-deoxyestreptamine, 16, which has an interesting synthetic challenge related to the presence of five continuous stereogenic centre with substituents in trans disposition in the ring, and may be employed in the construction of more complex molecules. The synthetic strategy proposed to prepare meso 2-deoxyestreptamine (16) involves a new methodology and was performed in two synthetic routes: (i) the synthesis of precursory carba-sugar (46) and (ii) the synthesis of (16) properly.
47
Yang, Grace. "Application of the Adaptive Poisson Boltzmann Solver on the investigation of the small oligonucleotide A-site model and 30S ribosomal subunit binding to aminoglycosidic antibiotics /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3170239.
Full text
48
Udumula, Venkata Reddy. "Synthesis, RNA Binding and Antibacterial Studies of 2-DOS Mimetics AND Development of Polymer Supported Nanoparticle Catalysts for Nitroarene and Azide Reduction." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6031.
Full textAbstract:
Project I 2-Deoxystreptamine (2-DOS), the most conserved central scaffold of aminoglycosides, is known to specifically recognize the 5'-GU-'3 sequence step through highly conserved hydrogen bonds and electrostatic interactions within and without the context of aminoglycosides (Figure 1a). We proposed that a novel monomeric unnatural amino acid building block using 2-DOS as a template would allow us to develop RNA binding molecules with higher affinity and selectivity than those currently available. Conjugating two or more of the monomeric building blocks by an amide bond would introduce extra hydrogen bonding donors and acceptors that are absent in natural aminoglycosides and increase specificity of binding to a target RNA through a network of hydrogen bonds. In addition, the amide conjugation between the monomeric building blocks places two GU-base recognizing amines at 5 Å… distance, which is equal to the distance of neighboring base stacks in dsRNAs We hypothesized that targeting dsRNAs containing multiple consecutive 5'-GU-'3 sequence steps would become possible by connecting two or more of the monomeric building blocks by amide bonds. According to the proposed hypothesis, we designed three dimeric 2-DOS compounds connected by an amide bond. These three targets include the dimeric 2-DOS substrate connected by an amide bond, the dimeric 2-DOS containing the sugar moiety from Neamine, and a dimeric 2-DOS connected by a urea linker. These compounds were then tested for sequence specific binding against 8 different RNA strands, and for antibacterial activity against E. coli, actinobacter baumannii and klebsiella. Project II A dual optimization approach was used for to enhance the catalytic activity and chemoselectivity for nitro reduction. In this approach the composition of the nanoparticles and electronics effects of the polymer were studied towards nitro reduction. Bimetallic Ruthenium-Cobalt nanoparticles showed exceptional catalytic activity and chemoselectivity compared to monometallic Ruthenium nanoparticles. The electronic effects of the polymer also had a significant effect on the catalytic activity of the bimetallic nanoparticles. The electron-deficient poly(4-trifluoromethylstyrene) supported bimetallic nanoparticles undergo nitro reduction in 20 minutes at room temperature, whereas electron-rich poly(4-methylstyrene) and poly(4-methoxystyrene) supported bimetallic nanoparticles to longer reaction times to go to completion. Electronics of the polymers also effects the change in mechanism of nitroreduction. Polystyrene bimetallic Ruthenium-Cobalt nanoparticles showed excellent yields and chemoselectivity towards nitro functional group in the presence of easily reducible functional groups like alkenes, alkynes, allyl ethers, propargyl ethers. Monometallic ruthenium nanoparticles also showed excellent reactivity and chemoselectivity towards azide reduction in the presence of easily reducible functional groups. Interestingly monometallic ruthenium nanoparticles showed regioselective reduction of primary azides in the presence of secondary and benzylic azides, also aromatic azides can be selectively reduced in the presence of secondary azides. These polystyrene supported nanoparticles are heterogeneous and are easily separated from the reaction mixture and reused multiple times without significant of catalytic activity.
49
Santos, Lucianne Leigue dos. "Caracterização de bactérias gram-negativas multirresistentes produtoras de β-lactamase-de-espectro-extendido (ESBL) em cavalos saudáveis e doentes." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-16112016-105643/.
Full textAbstract:
O objetivo deste estudo foi caracterizar bactérias multirresistentes (MDR) isoladas de cavalos saudáveis (fezes) e doentes no Brasil e na França. De março de 2012 a dezembro de 2014, amostras clínicas coletadas de cavalos saudáveis e doentes no Brasil foram selecionadas para pesquisa da presença de bactérias MDR. A investigação sobre as amostras franceses foi restria a isolados de Escherichia coli (EC) recuperados a partir de amostras clínicas coletadas entre 2014 e 2015. Nos cavalos brasileiros, a análise de amostras de fezes de animais saudáveis revelou a presença de clones de EC não relacionados pertencentes aos filogrupos A, D ou B2 que carreavam genes como: blaCTX-M-1, blaCMY-2, qnr- e genes add-tipo (amino-transferases); enquanto que nos cavalos doentes foram encontradas EC, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa e Serratia marcescens carreando genes blaCTX-M-15, blaCTX-M-1, rmtD 16S rRNA metilase, qnr-tipo, aac(6´)-Ib-cr e aad-tipo. Nos cavalos doentes franceses de EC MDR foram positivas para CTX-M-1, seguido de M-2- e M-9. Estes resultados destacam a importância de cavalos como um novo reservatório de bactérias MDR.The aim of this study was to characterize multidrug-resistant (MDR) bacteria isolated from healthy and infected horses in Brazil and France. From March 2012 to December 2014, clinical samples collected from healthy and infected horses, in Brazil, were screened for the presence of MDR bacteria. Investigation on French isolates was restricted to E. coli strains recovered from clinical samples collected between 2014 and 2015. In Brazilian horses, the analysis of fecal samples from healthy animals revealed the presence of clonally unrelated A, D or B2 phylogroups of E. coli strains carrying blaCTX-M-1, blaCMY-2, qnr- and aminoglycoside adenyl transferase (aad)-type genes, whereas in infected horses, E. coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens isolates carrying blaCTX-M-15, blaCTX-M-1, rmtD 16S rRNA methylase, qnr-type, aac(6´)-Ib-cr and aad-type genes. In French infected horses, most MDR E. coli isolates were positive for CTX-M-1-, followed by CTX-M-2- and CTX-M-9-type extended-spectrum beta-lactamases. These results highlight the importance of horses as a new reservoir of MDR bacteria.
50
Ntsogo, Enguene Véronique Yvette. "Nouvelle approche dans la lutte contre la résistance aux antibiotiques des bactéries colonisant les poumons des patients atteints de mucoviscidose : reconstitution d'une pompe d'efflux de Pseudomonas aeruginosa." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCB146/document.
Full textAbstract:
Les pompes d'efflux sont des complexes macromoléculaires qui permettent l'efflux des antibiotiques à travers les deux membranes (interne et externe). Ces pompes, spécifiques des bactéries Gram négatif, constituent l'un des acteurs majeurs du phénomène de résistance aux antibiotiques, en contribuant ainsi à la résistance intrinsèque et acquise de ces bactéries à de nombreuses molécules utilisées en antibiothérapie. Chez P. aeruginosa, ces pompes appartiennent pour la plupart à la famille des transporteurs RND. Ce sont des complexes tripartites constitués d'un transporteur de la membrane interne (RND), d'un adaptateur périplasmique (MFP) et d'un canal de la membrane externe (OMF). Ces composants ont été caractérisés individuellement chez de nombreuses bactéries. Cependant, les mécanismes qui régissent l'assemblage et la dissociation de la pompe, essentiels pour son fonctionnement, demeurent mal compris. Nous nous sommes donc intéressés au cours de ce travail aux pompes à efflux de Pseudomonas aeruginosa. Nous avons notamment procédé à la caractérisation structurale du canal OprN de la pompe MexEF-OprN impliquée dans la résistance aux fluoroquinolones et à la caractérisation biophysique du transporteur RND MexY de la pompe MexXY-OprM, spécifique des aminoglycosides. Nous avons étudié en parallèle le mécanisme d'ouverture du canal OprM seul in vitro (aspects structuraux) et in vivo (aspects fonctionnels) au sein de la pompe assemblée. Nos résultats montrent que les OMFs de P. aeruginosa présentent des similitudes avec les OMFs d'autres bactéries Gram négatif, mais également des différences, notamment pour OprN et OprM au niveau de l'interaction avec leurs partenaires ou encore pour OprM concernant l'ouverture du canal. Nous avons par ailleurs participé à l'étude in vitro de l'assemblage et du transport à travers la pompe MexAB-OprM, reconstituée au sein de protéoliposomes, confirmant l'importance de l'acylation de la MFP dans la formation du complexe et montrant l'importance de la force proto-motrice dans l'assemblage de la pompe mais pas dans sa dissociation. En parallèle de l'étude des pompes à efflux, nous nous sommes intéressés à un autre système de résistance, impliqué dans la dégradation des antibiotiques. Nous avons donc réalisé, en collaboration avec le Pr Patrick Plésiat (laboratoire de Bactériologie de Besançon), la modélisation de mutants de la beta-lactamase AmpC de P. aeruginosa, permettant de lier les effets fonctionnels observés à des hypothèses de modifications conformationnellesMultidrug efflux systems are membrane transport proteins that are used to translocate a wide variety of drugs across the inner and the outer membranes of Gram-negative bacteria, leading to natural and acquired antimicrobial resistances.Most of the multidrug transporters of P. aeruginosa belong to the resistance-nodulation-cell division (RND) superfamily.They function as three-component assemblies made of an inner membrane transporter (RND), a periplasmic membrane fusion protein (MFP) and an outer membrane factor channel (OMF). Along with functional studies, many crystal structures of the individual components of the pump have been solved but the interactions underlying the complex assembly and the opening mechanism of the outer channel remain unclear. In this study, we investigated structural and functional insights of P. aeruginosa efflux pumps. We solved the crystal structure of the MexEF-OprN efflux pump outer membrane channel OprN mainly involved in fluoroquinolones resistance. Our new structure highlights the differences between P. aeruginosa and other Gram-negative bacteria OMFs that could explain their specific interaction with the cognate MFP partners. We also purified and characterized the inner membrane transporter MexY from the MexXY-OprM efflux pump, which is the major determinant of aminoglycosides resistance in P. aeruginosa. Besides, we solved the crystal structure of a mutatedform of the outer membrane channel OprM in order to understand its opening mechanism. We also investigated in vivo effect of the OprM mutants in antibiotics resistance by MIC measurements and tried to correlate with the observed structural modifications leading to the open state. Moreover, we set up a new in vitro test allowing the investigation of the assembly of the MexAB-OprM efflux pump. Our results showed the importance of MexA and its lipid anchor in promoting and stabilizing the complex assembly. In addition, as a side project with the group of Pr Plésiat (laboratoire de Bactériologie de Besançon), we built different structural models of AmpC mutants from overproducing clinical isolates,showing the possible conformational changes that lead to the resistance increase