Frequency of Class B Carbapenemases (MbL) in enterobacteriacae

Objective: To determine the frequency of Metallo- -lactamase producing Enteriobacteriaceae species.Method: The descriptive cross-sectional study was carried out from January to December 2011 in the Department of Microbiology, Basic Medical Sciences Institute, Jinnah Postgraduate Medical Centre, Karachi. A total of 500 specimens were initially collected. The culture positive samples were analysed for further identification, and antimicrobial sensitivity was done according to Clinical and Laboratory Standards Institute guidelines 2009. The Carbapenemases Producing Enterobacteriaceae strains were screened by the Modified Hodge Test, and Metallo-b-Lactamase production was confirmed by the EDTA combined disc test.Result: From amongst 402 organisms detected, 200 (49.75%) were Enterobacteriaceae, while Escherichia coli was the leading pathogen (65%). Only 6% were identified as Carbapenemases Producing Enterobacteriaceae and 9 (75%) of them were Metallo-b-Lactamase producing strains, while 3 (25%) contained other enzymes.Conclusion: Metallo-b-Lactamase producing Enterobacteriaceae species are causing problems in tertiary care hospitals.