Genetic Environment Characterization of blaCTX-M-2 in Pseudomonas aeruginosa in Argentina

RUGGIERO MELINA; DI CONZA JOSÉ; FAMIGLIETTI ANGELINA; VAY CARLOS; RADICE MARCELA; GUTKIND GABRIEL

San Francisco, Ca.

Congreso; 49 th ICAAC - Interscience Conference on Antimicrobial Agents and Chemotherapy; 2009

ASM

Background: Production of plasmid-mediated extended-spectrum beta-lactamases (ESBLs) represents the most important strategy developed by microorganisms to impair the action of b-lactam antibiotics. CTX-M-2 is the most prevalent ESBL in our country, and has been, with CTX-M-3, the first members of this family to be associated to severe outbreaks produced by enterobacteria. However, little is known about dissemination to the "non-fermenters". blaCTX-M-2 has been described in unusual class 1 integron (associated to ISCR1 element) in many enterobacteria. The aim of this study was to characterize the genetic environment of this resistance marker in a clinical isolate of Pseudomonas aeruginosa. Methods: Susceptibility was determined by diffusion methods according to CLSI. Screening for ESBLs was performed by clavulanic acid synergy tests using ceftazidime and cefepime. bla genes were detected by PCR amplification on plasmid DNA and sequencing. Flanking sequences of blaCTX-M-2 were determined by PCR mapping strategy. PCR products were cloned into pGEM-T (Promega, USA) and sequenced in both strands. Results: The isolate was resistant to cefepime, ceftazidime, imipenem and other non b-lactam antibiotics. Positive synergy with clavulanic acid suggested the presence of an ESBL. PCR amplification for ESBL genes and amplicon sequencing indicated the presence of blaCTX-M-2 and blaGES-1. blaCTX-M-2 was located in an unusual class 1 integron with the same gene cassettes arrangement previously described in InS21 and In116. Conclusion: This finding strongly suggests the spread of blaCTX-M-2 as part of "resistance island" that is being movilized not only within enterobacteria but also moving into the non-fermenters bacilli.