Extended-Spectrum Beta-Lactamases Producing Escherichia coli and Klebsiella pneumoniae: A Multi-Centric Study Across Karnataka

BACKGROUND: There are sporadic reports on detection of extended-spectrum beta-lactamases (ESBL) producers from Karnataka; hence, this is a first multicentric study across Karnataka state to determine the prevalence of ESBL production among clinical isolates of Escherichia coli and Klebsiella pneumoniae. AIMS AND OBJECTIVES: To determine the prevalence of ESBL producing clinical isolates of E. coli and K. pneumoniae from five geographically distributed centers across Karnataka, to study the susceptibility of ESBL producing isolates to other beta-lactam and beta-lactam-beta-lactamase inhibitors and to demonstrate transferability of plasmids coding for ESBL phenotype. MATERIALS AND METHODS: Two hundred isolates of E. coli and K. pneumoniae each were collected from each of the five centers (Bellary, Dharwad, Davangere, Kolar and Mangalore). They were screened for resistance to screening agents (ceftazidime, cefotaxime, ceftriaxone, aztreonam) and positive isolates were confirmed for ESBL production by test described by Clinical and Laboratory Standards Institute. Co-production of ESBL and AmpC beta-lactamase was identified by using amino-phenylboronic acid disk method. Susceptibility of ESBL producers to beta-lactam antibiotics and beta-lactamase inhibitors was performed. Transferability of plasmids was performed by conjugation experiment. RESULTS: Overall prevalence of ESBL production among E. coli and K. pneumoniae across five centers of the state was 57.5%. ESBL production was found to be 61.4% among E. coli and 46.2% among K. pneumoniae. ESBL production was significantly more among E. coli than K. pneumoniae. Significant variations in distribution of ESBL across the state was observed among E. coli isolates, but not among K. pneumoniae isolates. All ESBL producers demonstrated minimum inhibitory concentration levels ≥2 μg/ml towards cefotaxime, ceftazidime and ceftriaxone. CONCLUSION: Overall prevalence of ESBL production among clinical isolates of E. coli and K. pneumoniae across Karnataka state was high. The prevalence of ESBL production was significantly higher with E. coli than K. pneumoniae isolates. Higher rates of resistance to ceftriaxone and cefotaxime than to ceftazidime suggests the possibility of presence of CTX-M type ESBLs. Of all the beta-lactam/beta-lactamase inhibitor combinations tested, cefepime-tazobactam demonstrated highest in-vitro activity against ESBL producers. There was no statistical difference in the transferability of plasmids among E. coli and K. pneumoniae.