Horieh Saderi - Faculty of Medicine, Shahed University, Tehran, Iran.
Zohreh Karimi - Faculty of Medicine, Shahed University, Tehran, Iran
Parviz Owlia - Faculty of Medicine, Shahed University, Tehran, Iran
Mohammad Ali Bahar - Shahid Motahari Hospital , Iran University of Medical Sciences, Tehran, Iran

Background and Objective: Metallo-beta-lactamases (MBLS) mediated resistance is an emerging threat in hospital isolates of Pseudomonas aeruginosa. There is not enough information fromIran regarding the prevalence and the screening methods for such enzymes. The present study was undertaken to detect MBLS in strains of P. aeruginosa isolated from burned patient using phenotypic method. Materials and Methods: For this purpose, 128 consecutive P. aeruginosa isolates obtainedfrom hospitalized patients were subjected to susceptibility testing to antipseudomonal drugs by disc diffusion and minimal inhibitory concentration (MIC) for ceftazidime was determined. The production of MBL was detected by the zone size enhancement with EDTA impregnated ceftazidimedisc. Results: It was found out that 94 (73.44%) of the isolates were resistant to ceftazidime. Theseisolates screened as ESBLs producing strains and introduced for detection of MBL production. Out of the 94 P. aeruginosa that were resistant to ceftazidime, 50 (53.2%) isolates were MBL positive.This result indicated that 39.06% of all isolates were MBL positive.Conclusion: MBL-mediated ceftazidime resistance in P. aeruginosa is a cause for concern in the therapy of critically ill patients. The MBL producing P. aeruginosa isolates were more resistantto various antimicrobial agents. This result suggests that MBL producing isolates in hospitalsmay cause serious infections that illustrated when these strains were responsible for a nosocomial outbreak.

Ceftazidime, Metallo-beta-lactamase, Pseudomonas aeruginosa