SCREENING OF METALLO-ΒETA-LACTAMASE-PRODUCING PSEUDOMONAS AERUGINOSA IN UNIVERSITY HOSPITAL IN RIBEIRÃO PRETO – SP

AC31

Renata Galetti (1) regaletti@hotmail.com, Leonardo Neves de Andrade (1), Eduardo Carneiro Clímaco (1), Joseane Cristina Ferreira (1), Roberto Martinez (2), Ana Lúcia da Costa Darini (1)

(1) Faculdade de Ciências Farmacêuticas de Ribeirão Preto – USP, (2) Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto - USP

Introduction: The metallo-beta-lactamase (MBL) production is an important mechanism of  carbapenem resistance in Pseudomonas aeruginosa. These enzymes are part of Ambler class B beta-lactamases and they hydrolyze all beta-lactams antibiotics, except aztreonam. This fact severely restrictis treatment options against many Gram-negative rods, including P. aeruginosa. MBL are not inhibited by commercially available beta-lactamase inhibitors. As these enzymes require two ions divalentes, commonly zinc, as cofactor for your activity, they have sensitivity to ethylene diamine tetracetic acid (EDTA) and mercaptopropionic acid (MPA). Actually, six subclasses of MBL are known: IMP, VIM. SPM, SIM, GIM, AIM. Objective: The aim of the present study was to screen and detect MBL-producing P. aeruginosa isolated from patients hospitalized at the Hospital das Clínicas de Ribeirão Preto - USP in the period of April to August, 2007. Material and Methods: All imipenem, meropenem or ceftazidime-resistant P. aeruginosa isolates were recovered from hospitalized patients admitted in this instituition. The isolates were submitted to screening for MBL production with ceftazidime and imipenem in the presence of MPA and EDTA using double-disk synergy test (DDS). Isolates that presented ghost zone in the DDS was considered as presumptive MBL-producers, and these will be submitted to polymerase chain reaction (PCR) for detection of resistance genes. Results: P. aeruginosa isolates were obtained from urine (31 isolates, 41,33%), sputum (16 isolates, 21,33%), catheter (6 isolates, 8%) and blood (5 isolates, 6,66%). Seventeen (22,67%) isolates were obtained from others sites. Seventy-five isolates were resistant to ceftazidime and/or imipenem/meropenem. Thirty-five out of 75 isolates, corresponding to 46,7%, were presumptive MBL-producers according to DDS. Conclusion: The founded results about MBL-producers indicates the necessity of measures to controlling the special of resistance to carbapenens.