Antibiotic resistance pattern of metallo-beta-lactamase producing and non-producing clinical isolates of Pseudomonas aeruginosa in Mashhad

Zinc-dependent beta-lactamases inactivate a wide range of beta-lactam drugs, especially the carbapenem. One of the causes of antibiotic resistance in Pseudomonas aeruginosa is production of these enzymes. The aim of the present study was to identify clinical isolates of P. aeruginosa in Mashhad based on biochemical and molecular methods and to compare the antibiotic resistance pattern between methallo-beta-lactamase (MBL)-producing isolates and nonproducers. In this study, 64 clinical isolates of P. aeruginosa were collected and identified from various samples of patients in 2012. Confirmatory identification of bacteria was performed using polymerase chain reaction and specific 16S rRNA primers. MBL-producers were identified by using imipenem disk adjacent to a disk containing imipenem and EDTA. Antibiotic susceptibility assay was performed by agar diffusion method based on standard Kirby-Bauer method. Out of 64 bacterial isolates, 22 (34.38%) were MBLproducers which 81.8% were resistance to imipenem. Among MBL-producers, resistance to meropenem, imipenem, ceftazidime, and carbenicillin were significantly higher than non- MBL-producing bacteria (p < 0.05). This study shows the high number of MBLproducing Pseudomonas aeruginosa in studied community and increased resistance to imipenem among them. It appears the prevalence of MBL-producing strains to be increasing in our country which emphasize the need for further strategies on antibiotic prescribing management and control of antibiotic resistance.