Estudo das betas-lactamases envolvidas na resistência às cefaloproteínas de amplo espectro em isolados clínicos de Pseudomonas aeruginosa
Arquivos
Data
2009
Autores
Picão, Renata Cristina 
Orientadores
Gales, Ana Cristina
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O presente estudo teve como objetivo determinar as β)lactamases envolvidas na resistência às cefalosporinas de amplo espectro em uma coleção de Pseudomonas aeruginosa isoladas de hemoculturas de pacientes internados em um complexo hospitalar universitário na cidade de São Paulo durante o ano de 2005. No primeiro trabalho descrevemos a produção de CTX)M)2 em um isolado que apresentava o estranho fenótipo de sensibilidade à ceftazidima e resistência à cefepima. O gene que codificava esta enzima estava localizado no cromossomo bacteriano, em um contexto genético idêntico àquele encontrado em plasmídeos que carregam blaCTX)M)2, que encontram)se disseminados entre enterobactérias. No segundo trabalho, descrevemos as β)lactamases envolvidas na resistência à ceftazidima em 43 isolados de P. aeruginosa da referida coleção, assim como o contexto e suporte no qual estavam inseridos os genes que codificavam as enzimas identificadas. Além disso, realizamos a tipagem molecular dos isolados estudados e pesquisamos os prontuários médicos dos pacientes infectados pelas amostras estudadas. A hiperprodução de AmpC foi considerada a única β)lactamase relacionada à resistência a ceftazidima em quatro isolados (9,3 por cento). Nove isolados (20,9 por cento) apresentaram a produção de β)lactamase de espectro estendido (ESBL), sendo que sete (16,3 por cento) apresentavam a enzima GES)1 e dois isolados (4,6 por cento) apresentavam a enzima CTX)M)2. A atividade hidrolítica contra os carbapenens foi detectada em trinta isolados (69,7 por cento), nos quais as enzimas IMP)1, GES) 5 e SPM)1 foram identificadas em 1, 2 e 27 isolados, respectivamente. Nenhum isolado apresentou produção simultânea de metalo)β)lactamase e ESBL. Os genes blaSPM)1 e blaCTX)M)2 estavam associados às seqüências de inserção ISCR4 e ISCR1, respectivamente, enquanto que os genes blaGES)1, blaGES)5 e blaIMP)1 estavam localizados em integrons da classe 1. Todos os genes codificadores de β)lactamases identificados apresentavam localização cromossomal. A tipagem molecular dos isolados estudados evidenciou a existência de sete genótipos distintos; porém, isolados produtores de uma mesma enzima freqüentemente apresentavam relação clonal. A análise dos prontuários médicos revelou que metade dos pacientes que apresentaram infecção da corrente sanguínea pelos isolados de P. aeruginosa estudados receberam terapia inadequada. Este estudo permitiu identificar a diversidade de genes codificadores de β)lactamases de amplo espectro hidrolítico que foram adquiridos por isolados clínicos de P. aeruginosa. Estes genes foram inseridos no DNA cromossomal destes isolados e, posteriormente, disseminados por transmissão cruzada..
The aim of this study was to identify the β-lactamases involved in broad-spectrum cephalosporin resistance in P. aeruginosa isolates recovered from blood culture of patients hospitalized at a Brazilian teaching hospital located in São Paulo, between January and December 2005. In the first manuscript we have described the production of CTX-M-2 causing ceftazidime susceptibility and cefepime resistance in a P. aeruginosa clinical isolate. The CTX-M-2-encoding gene was located at the bacterial chromosome, and its vicinities were identical to those observed in blaCTX-M-2-carrying plasmids from enterobacterial isolates. In the second manuscript we have evaluated 43 ceftazidime-resistant P. aeruginosa isolates from the referred collection. We have described the β-lactamases involved in ceftazdidme resistance, as well as the genetic context and support of β-lactamaseencoding genes and we have performed molecular typing of isolates. The medical records of patients infected with isolates studied were also analyzed. AmpC overproduction was found to be the only β-lactamase-mediated mechanism responsible for ceftazidime resistance in four isolates (9.3%). Nine isolates (20.9%) produced an extended-spectrum β-lactamase (ESBL), either GES-1 (n = 7, 16.3%) or CTX-M-2 (n = 2, 4.6%). Carbapenemase activity was detected in 30 (69,7%) isolates, in which two (4.6%) produced the ESBL GES-5, a single isolate (2.3%) produced the metallo-β-lactamase (MBL) IMP-1; and 27 isolates produced the MBL SPM-1 (62.8%). None of the isolates coproduced both ESBL and MBL. Insertion sequence elements ISCR4 and ISCR1 were associated with blaSPM-1 and blaCTX-M-2 genes, respectively, whereas the blaGES and blaIMP-1 genes were part of class 1 integron structures. All β- lactamase-encoding genes identified were chromosomally located. Molecular typing showed the existence of seven distinct genotypes, in which producers of the same β- lactamase often belonged to a single clone. Clinical data revealed that half of the patients infected with isolates studied have received inadequate therapy, suggesting that empirical treatment protocols should be updated in the hospital studied. In this study we have identified a variety of broad-spectrum β-lactamase-encoding genes that have been initially acquired by P. aeruginosa clinical isolates, inserted on its chromosomal DNA and then spread between patients by cross-transmition.
The aim of this study was to identify the β-lactamases involved in broad-spectrum cephalosporin resistance in P. aeruginosa isolates recovered from blood culture of patients hospitalized at a Brazilian teaching hospital located in São Paulo, between January and December 2005. In the first manuscript we have described the production of CTX-M-2 causing ceftazidime susceptibility and cefepime resistance in a P. aeruginosa clinical isolate. The CTX-M-2-encoding gene was located at the bacterial chromosome, and its vicinities were identical to those observed in blaCTX-M-2-carrying plasmids from enterobacterial isolates. In the second manuscript we have evaluated 43 ceftazidime-resistant P. aeruginosa isolates from the referred collection. We have described the β-lactamases involved in ceftazdidme resistance, as well as the genetic context and support of β-lactamaseencoding genes and we have performed molecular typing of isolates. The medical records of patients infected with isolates studied were also analyzed. AmpC overproduction was found to be the only β-lactamase-mediated mechanism responsible for ceftazidime resistance in four isolates (9.3%). Nine isolates (20.9%) produced an extended-spectrum β-lactamase (ESBL), either GES-1 (n = 7, 16.3%) or CTX-M-2 (n = 2, 4.6%). Carbapenemase activity was detected in 30 (69,7%) isolates, in which two (4.6%) produced the ESBL GES-5, a single isolate (2.3%) produced the metallo-β-lactamase (MBL) IMP-1; and 27 isolates produced the MBL SPM-1 (62.8%). None of the isolates coproduced both ESBL and MBL. Insertion sequence elements ISCR4 and ISCR1 were associated with blaSPM-1 and blaCTX-M-2 genes, respectively, whereas the blaGES and blaIMP-1 genes were part of class 1 integron structures. All β- lactamase-encoding genes identified were chromosomally located. Molecular typing showed the existence of seven distinct genotypes, in which producers of the same β- lactamase often belonged to a single clone. Clinical data revealed that half of the patients infected with isolates studied have received inadequate therapy, suggesting that empirical treatment protocols should be updated in the hospital studied. In this study we have identified a variety of broad-spectrum β-lactamase-encoding genes that have been initially acquired by P. aeruginosa clinical isolates, inserted on its chromosomal DNA and then spread between patients by cross-transmition.
Descrição
Citação
PICÃO, Renata Cristina. Estudo das β-lactamases envolvidas na resistência às cefalosporinas de amplo espectro em isolados clínicos de Pseudomonas aeruginosa. 2009. 136 f. Tese (Doutorado em Ciências) – Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, 2009.