Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates

Bibliographic Details
Main Author: Mendonça, Nuno Ricardo Furtado Dias
Publication Date: 2009
Language: eng
Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
Download full: http://hdl.handle.net/10362/2046
Summary: Dissertation presented to obtain a Ph.D. degree in Biology, speciality Microbiology, by Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia
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spelling Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolatesKlebsiella pneumoniaeEscherichia coliMolecular diversityDisseminationβ-lactamasesAntimicrobial resistanceDissertation presented to obtain a Ph.D. degree in Biology, speciality Microbiology, by Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaAntimicrobial resistance is a growing problem worldwide, with extended-spectrum β- lactamase (ESBL)-producing organisms remaining an important cause of cephalosporin therapy failure. The main purpose of the work presented in this dissertation was to search for the molecular diversity of Ambler class A β-lactamase encoding genes in clinical Klebsiella pneumoniae and Escherichia coli isolates and its consequences. In a first step, the evaluation of ESBL detection and confirmation methods for K. pneumoniae, using different guidelines, was performed, with nucleotide sequencing allowing the identification of a new ESBL (SHV-55). The enzymatic properties of this new β-lactamase confirmed a higher affinity towards extended-spectrum cephalosporins, which is characteristic of ESBLs, contrasting to the parental enzyme SHV-1. For the new β-lactamase SHV-72, the higher value of 50% inhibitory concentration of clavulanic acid than for SHV-1 correlated with the values of higher afinity towards penicillins,which are characteristic of an inhibitor resistance enzyme. Simulation of molecular dynamics suggested that the Lys234Arg substitution in SHV-72 was responsible for stabilizing an atipical conformation of the Ser130 side chain, which may decrease susceptibility to clavulanic acid by preventing cross-linking between Ser130 and Ser70. Among the collection of K. pneumoniae strains studied, we identified several genes coding for different enzymes belonging to the CTX-M, GES, LEN, OKP, OXA, TEM, and SHV families and, among them, 35 were new β-lactamases. Among ESBL-producing isolates from 1999 and 2006, we detected the presence of CTX-M enzymes only in the latest period. Overall, the complex molecular diversity of the blaSHV genes detected impelled us to propose a classification for this gene family, based on nucleotide synonymous mutations and the presence or absence of the nonsynonymous mutation T92A. Finally, among E. coli isolates colected in Portugal, a predominat multidrug resistant clone, producing TEM, OXA and CTX-M enzymes, was present in different hospital wards and community environments. The high dissemination of the CTX-M enzymes detected could also be associated with horizontal transfer of plasmids or mobile elements, like ISEcp1. In Algeria, we identified the same insertion sequence in clinical E. coli strains producing TEM and either CTX-M-3 or CTX-M-15 β-lactamases. In conclusion, the results from this dissertation extended our knowledge about the most important mechanism of resistance – the β-lactamases production – focusing on the phenotypic characteristics, biochemical properties, structure-function relationships, molecular diversity and dissemination, which are of most importance to the comprehension of the general resistance scenario in Portugal and worldwide.FCT - UNLCaniça, ManuelaRUNMendonça, Nuno Ricardo Furtado Dias2009-09-14T13:42:17Z20092009-01-01T00:00:00Zdoctoral thesisinfo:eu-repo/semantics/publishedVersionapplication/pdfhttp://hdl.handle.net/10362/2046enginfo:eu-repo/semantics/openAccessreponame:Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)instname:FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiainstacron:RCAAP2024-05-22T17:06:40Zoai:run.unl.pt:10362/2046Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireinfo@rcaap.ptopendoar:https://opendoar.ac.uk/repository/71602025-05-28T16:37:51.665168Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) - FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiafalse
dc.title.none.fl_str_mv Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
title Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
spellingShingle Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
Mendonça, Nuno Ricardo Furtado Dias
Klebsiella pneumoniae
Escherichia coli
Molecular diversity
Dissemination
β-lactamases
Antimicrobial resistance
title_short Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
title_full Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
title_fullStr Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
title_full_unstemmed Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
title_sort Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
author Mendonça, Nuno Ricardo Furtado Dias
author_facet Mendonça, Nuno Ricardo Furtado Dias
author_role author
dc.contributor.none.fl_str_mv Caniça, Manuela
RUN
dc.contributor.author.fl_str_mv Mendonça, Nuno Ricardo Furtado Dias
dc.subject.por.fl_str_mv Klebsiella pneumoniae
Escherichia coli
Molecular diversity
Dissemination
β-lactamases
Antimicrobial resistance
topic Klebsiella pneumoniae
Escherichia coli
Molecular diversity
Dissemination
β-lactamases
Antimicrobial resistance
description Dissertation presented to obtain a Ph.D. degree in Biology, speciality Microbiology, by Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia
publishDate 2009
dc.date.none.fl_str_mv 2009-09-14T13:42:17Z
2009
2009-01-01T00:00:00Z
dc.type.driver.fl_str_mv doctoral thesis
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
status_str publishedVersion
dc.identifier.uri.fl_str_mv http://hdl.handle.net/10362/2046
url http://hdl.handle.net/10362/2046
dc.language.iso.fl_str_mv eng
language eng
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv FCT - UNL
publisher.none.fl_str_mv FCT - UNL
dc.source.none.fl_str_mv reponame:Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
instname:FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
instacron:RCAAP
instname_str FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
instacron_str RCAAP
institution RCAAP
reponame_str Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
collection Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
repository.name.fl_str_mv Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) - FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
repository.mail.fl_str_mv info@rcaap.pt
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