Frequency and susceptibility pattern of metallo-beta-lactamase producers in a hospital in Pakistan.

INTRODUCTION The rapid spread of acquired metallo-beta-lactamases (MBLs) among major Gram-negative pathogens is an emerging threat and a matter of particular concern worldwide. METHODOLOGY This descriptive study was conducted between January and August 2009 in the department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, to determine the frequency and susceptibility patterns of MBL-producers among carbapenem-resistant Gram-negative rods (GNRs) from clinical isolates of a tertiary care hospital. All clinical samples were processed according to standard microbiological methods. Isolated GNRs were subjected to susceptibility testing against various antibiotics by disc diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines.  Carbapenem-resistant isolates were subjected to the detection of MBL production by the E-test MBL strip method. RESULTS Out of 50 carbapenem resistant isolates, 39 (78%) of were confirmed to be MBL producers by the E-strip method.  Acinetobacter baumannii were the most frequent MBL producers, followed by Pseudomonas aeruginosa. A total of 19 (37%) of the MBL producers were susceptible to cefoperazone-sulbactam. CONCLUSION The findings strongly suggest that there is a need to track the detection of MBL producers and that judicious use of carbapenems is necessary to prevent the further spread of these organisms.