Extended spectrum beta-lactamase production in clinical isolates from hospitals at Kolkata

Clinical isolates resistant to beta-lactam antibiotics have become an ever-increasing problem, especially due to the production of Extended-Spectrum beta-lactamases (ESBLs) that can hydrolyze a wide spectrum of beta-lactam antibiotics. The present study was undertaken to assess the prevalence of ES6L producers in major hospitals of Kolkata. 284 non-repeat clinical isolates were taken from five major hospitals of Kolkata and screened for ES6L production by Disk Agar Diffusion (DAD) using third generation cephalosporins (3GC) and Double Disk Synergy Test (DDST) with and without clavulanic acid (CA), as per National Committee for Clinical Laboratory Standards (NCCLS). 87 (30.6%) strains were resistant to at least two 3GC out of which 46 (16.2%) were found to be ESBL-producers and confirmed phenotypically by DDST. We found ES6L production in 26 (56.5%) of Escherichia coli, 12 (26.1%) of Klebsiella pneumonias, 4 (8.6%) of Klebsiella spp., 2 (4.3%) of Pseudomonas aeruginosa, 2 (4.3%) of Proteus vulgaris. Some of the representative isolates were screened for the presence of plasmid DNA. Both large and small plasmids were found in these strains. We report a finding of 16.2% of ES6L producing clinical strains from Kolkata. ES6L producers can cause a major therapeutic failure in Kolkata if not detected and reported in time.