COMPARISON OF DIFFERENT PHENOTYPIC METHODS FOR THE DETECTION OF EXTENDED SPECTRUM BETA LACTAMASES IN ESCHERICHIA COLI AND IN AMP C CO-PRODUCING PHENOTYPES THROUGH SINGLE PLATE DETECTION TECHNIQUE

Objectives: The study was done to determine the prevalence of Extended spectrum beta lactamases (ESBL) in urinary isolates of Escherichia coli ( E. coli) and to evaluate and compare different phenotypic methods for its detection through single plate detection technique, even in AmpC co-producing ESBL phenotypes of E.coli. Study design: Cross sectional comparative. Place and duration of study: The study was done in the Department of Microbiology, Combined Military Hospital, Lahore, Pakistan from January 2016 to June 2016. Materials & Methods: Out of 945 samples for urine culture, received from various units of CMH Lahore, 70 specimens yielded growth of E. coli . In single plate screening technique, E.coli isolates were tested by Double disk synergy test (DDST) and Modified double disk synergy test (MDDST) using Cefepime (FEP) & Piperacillin-tazobactam (TZP) on a single plate for the detection of ESBL to save time and money. Phenotypic confirmatory disk diffusion method (PCDDT) was taken as “Gold Standard”. Results: From 70 E coli isolates , 34 were positive for ESBL production. DDST detected ESBL in 12/34 isolates. MDDST detected ESBL in 33/34 isolates including 14 isolates that were co-producers. Therefore, MDDST proved to be very effective in detecting ESBL in AmpC co-producing E.coli . Conclusion: The prevalence of ESBL producing E coli in our hospital was 48.75%. Single plate screening technique seems to be convenient and time saving (within 24 hrs) and increases the probability of detecting ESBL through different methods even in Amp C co-producing E.coli . Key words: ESBL, Amp C, DDST, MDDST.