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Doctoral Thesis
DOI
https://doi.org/10.11606/T.9.2015.tde-09112015-155733
Document
Author
Full name
Andrey Guimarães Sacramento
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2015
Supervisor
Committee
Mamizuka, Elsa Masae (President)
Huenuman, Nilton Erbet Lincopan
Garcia, Doroti de Oliveira
Martino, Marines Dalla Valle
Neves, Carla Taddei de Castro
Title in Portuguese
Caracterização molecular de Enterococcus spp. resistentes à vancomicina em amostras clínicas, ambientes aquáticos e alimentos
Keywords in Portuguese
Enterococcus
IS1216E
MLST
Multirresitentes
VanA
Abstract in Portuguese
Enterococos são ubíquos no ambiente e fazem parte da microbiota do trato gastrintestinal de humanos e animais. A importância dessas bactérias tem sido associada com infecções hospitalares e resistência a múltiplas drogas, principalmente à vancomicina. O objetivo do presente estudo foi realizar a caracterização molecular de cepas de Enterococcus spp. resistentes à vancomicina (VRE) isoladas a partir de amostras coletadas de pacientes hospitalizados, água superficial de rios urbanos e carne de frango comercializada no Brasil. A presença do gene vanA foi confirmada em 20 cepas multirresitentes isoladas durante 1997-2011. Dentre os isolados VRE, 12 cepas foram identificadas como E. faecium e oito como E. faecalis. Cepas de E. faecium isoladas de amostras clínicas e águas foram classificadas como clonalmente relacionadas pelo PFGE, com perfil virulência predominante (acm+, esp+). Adicionalmente, enquanto cepas de E. faecium isoladas dos rios pertenceram aos ST203, ST412 e ST478 (previamente caracterizados como endêmicos em hospitais brasileiros), novos STs foram identificados entre as cepas de E. faecalis (ST614, ST615 e ST616) e E. faecium (ST953 e ST954) isoladas de alimentos. Sequências completas do transposon Tn1546 das cepas clínicas VREfm 320/07 (ST478) e ambiental VREfm 11 (ST412) mostraram Tn1546-like element de ~12800 pb, com um ponto de mutação no gene vanA na posição 7.698 (substituição do nucleotídeo T pelo C) e uma no gene vanX na posição 8.234 (G pelo T). Além disso, uma deleção na extremidade esquerda do Tn1546, e as sequências IS1251 e IS1216E na região intergênica vanHS e vanYX, respectivamente, também foram detectados. A este respeito, a IS1216E na região intergênica vanXY constitui um conjunto de genes previamente relatado em cepas clínicas de VREfm no Brasil, denotando uma característica regional. IS1216E tem sido associada com os genes tcrB e aadE que conferem resistência ao cobre e aminoglicosídeos, em E. faecium e Streptococcus agalactiae, respectivamente. Portanto, essa IS pode contribuir para a rápida aquisição de resistência antimicrobiana entre as espécies de cocos Gram-positivos clinicamente importantes. Os tipos de Tn1546 indistiguíveis que foram identificados no atual estudo isolados de humano e ambientes aquáticos sugerem uma comum partilha de um pool de genes de resistência à vancomicina.
Title in English
Molecular characterization of vancomycin-resistant Enterococcus spp. in clinical samples, aquatic environments and foods
Keywords in English
Enterococcus
IS1216E
MLST
Multidrug-resistant
vanA
Abstract in English
Enterococci are ubiquitous in the environment and in the intestinal tract of humans and animals. The importance of these bacteria has been associated with nosocomial infection and multiple resistance to antimicrobial agents, mainly vancomycin. The aim of the present study was to perform molecular characterization of vancomycin-resistant Enterococcus spp. strains (VRE) isolated from hospitalized patients, surface water of urban rivers and retail chicken meat in Brazil. The presence of the vanA gene was confirmed in 20 multidrug-resistant strains isolated in 1997-2011. Among these VRE isolates, (n = 12) were identified as E. faecium and (n = 8) as E. faecalis. E. faecium strains isolated from water and clinical samples were classified as clonally related by PFGE, the predominant virulence profile being (acm+, esp+). Additionally, while E. faecium strains isolated from rivers belonging to ST203, ST412 and ST478 (previously characterized as endemic in Brazilian hospitals), new STs were identified among strains of E. faecalis (ST614, ST615 and ST616) and E. faecium (ST953 and ST954) isolated from food. Complete sequences of transposon Tn1546 from VREfm clinical strain 320/07 (ST478) and environmental strain VREfm 11 (ST412) showed a Tn1546-like element of ~12800 bp, with T7698C vanA and G8234T vanX mutations. Moreover, deletion of the Tn1546 left extremity, and the IS1251 and IS1216E sequence inside the vanHS and vanYX intergenic region, respectively, were also detected. In this regard, the IS1216E sequence inside the vanXY intergenic region constitutes a gene array previously reported for Brazilian VREfm clinical strains alone, denoting a regional characteristic. IS1216E has been associated with tcrB and aadE genes, which confer resistance to copper and aminoglycosides, in E. faecium and Streptococcus agalactiae, respectively. Therefore, IS1216E should contribute to rapid acquisition of antimicrobial resistance among species of the clinically important Gram-positive cocci. On the other hand, Tn1546-like elements were identical among clinical and environmental VREfm isolates, suggesting sharing of a common vancomycin resistance gene pool.
 
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Publishing Date
2015-11-19
 
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