Prevalência de beta-lactamases de amplo espectro e metilases RNAr 16S em isolados clínicos de Pseudomonas aeruginosa multirresistentes recuperados em diferentes hospitais de São Paulo / Prevalence of Extended-spectrum beta-lactamase and 16S rRNA methylases in clinical isolates of multidrug-resistant Pseudomonas aeruginosa recovered from differents hospitals in São Paulo

Mariama Tomaz Nogueira da Silva

Introduction and aim: The production of extended-spectrum beta-lactamases (ESBLs) has been restricted to Klebsiella spp. and Escherichia coli, being associated with high rates of resistance, morbidity and mortality. Since genetic determinants for ESBLs (blaESBL genes) are mediated by plasmids, the spread to other medical important species is considered an epidemiological urgency. These genes encoding ESBLs are commonly found in members of the Enterobacteriaceae however, plasmids, integrons, and insertion sequences have contributed to the increase in the incidence of blaESBL genes among other gram-negative bacteria, including Pseudomonas aeruginosa. Unfortunately, one of the biggest difficulties associated with the early identification of the production of ESBL in nosocomial agents as Pseudomonas aeruginosa has been the standardization of phenotypic methods, which are affected by false-negative results stemming from intrinsic mechanisms which can mask the presence of these enzymes (i.e., production of chromosomal beta-lactamase AmpC). The aim of this study is to characterize phenotypical and genotypical ESBL production in clinical isolates of P. aeruginosa recovered in different hospitals in São Paulo during the period of 2004 to 2008. Materials and methods: 35 P .aeruginosa isolates intermediately resistant or resistant to third generation cephalosporin were phenotypically analyzed for the presence of ESBL with and without inhibitors (clavulanic acid and cloxacilin).Genotipic confirmation with specific primers for blaCTX-M, blaTEM, blaSHV, blaOXA, blaPER and blaGES and the characterization of the genetic environment of blaCTX-M was performed by PCR and DNA sequencing.The random amplified polymorphism DNA technique with primer ERIC-2 was carried out for the isolates genotyping and the similarity index calculated with coefficient of Dice. Results and conclusion: the phenotypic methods identified 3 ESBL producing strains, however, the presence of genes blaCTX-M and blaOXA-10 has been confirmed in 9 (33%) and 2 (7%) strains of P. aeruginosa, respectively, from 3 medical centers. The mapping and sequencing of integron class 1 revealed that two strains harbored two different class 1 integrons with aadA6-like , aac6 gene and blaCTX-M-2-like genes conferring resistance to aminoglicosydes and third generation cephalosporins. The blaESBL horizontal transferation has not been confirmed by transformation. This study describes that the emergence and spread of genes blaCTX-M in clinical isolates of P. aeruginosa in Brazil had its origin from 2005. Since CTX-M type ESBLs have been widely described in Enterobacteriaceae, the identification of these genes in P. aeruginosa is alarming and shows that the blaCTX-M horizontal mobilization among different genus and species is a reality in Brazil. The genes that confer resistance to 16s RNAr methylases are not related to ESBL positive Pseudomonas aeruginosa strains in samples of São Paulo. The Pseudomonas aeruginosa strains of this study showed several genetic mobilization elements, such as integrons and insertion sequences, which may be participating in the spread of resistance to broad spectrum betalactams.

AUTOR(ES)

DATA DE PUBLICAÇÃO

RESUMO

ASSUNTO(S)

ACESSO AO ARTIGO

Documentos Relacionados