Molecular characterization of extended-spectrum β-lactamases among clinical isolates of Escherichia coli & Klebsiella pneumoniae: A multi-centric study from tertiary care hospitals in India

BACKGROUND & OBJECTIVES: The increasing prevalence of extended-spectrum β-lactamases (ESBLs) has abated therapeutic options worldwide. This study was undertaken to investigate the molecular profile and resistance patterns of ESBLs among clinical isolates of Escherichia coli and Klebsiella pneumoniae at four tertiary care centres in India. METHODS: Clinical isolates of E. coli and K. pneumoniae were collected from the All India Institute of Medical Sciences (AIIMS), New Delhi; the Jawaharlal Institute of Postgraduate Medical Education & Research (JIPMER), Puducherry; Postgraduate Institute of Medical Education & Research (PGIMER), Chandigarh and Christian Medical College (CMC), Vellore, over one and a half year period. Antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion method. ESBLs were confirmed phenotypically, and multiplex PCR was performed to identify genes for β-lactamases (bla(TEM), bla(SHV), bla(OXA-1), bla(CTXM-1), bla(CTXM-2), bla(CTXM-9) and bla(CTXM-15)). RESULTS: Among 341 E. coli isolates collected during the study period, 171 (50%) harboured bla(TEM), 145 (43%) bla(OXA-1), 70 (21%) bla(CTXM-1), 19 (6%) bla(SHV) and four (1%) harboured bla(CTXM-2). Phenotypically, combined disc test detected ESBL production in 98/298 (33%) E. coli. Among 304 K. pneumoniae isolates, 115 (38%), 89 (29%), 83 (27%), 64 (21%) and two (0.6%) harboured bla(TEM), bla(OXA-1), bla(CTXM-1), bla(SHV) and bla(CTXM-2), respectively. Combined disc test (CDT) detected ESBL production in 42 per cent K. pneumoniae. Most of the bla(CTXM-1) positive isolates were also bla(CTXM-15) positive. The carbapenem susceptibility ranged from 56 to 88 per cent for E. coli and from 20 to 61 per cent for K. pneumoniae. Antibiotic sensitivity patterns showed that colistin (CST) was the most sensitive drug for both E. coli (271/274, 99%) and K. pneumoniae (229/234, 98%). INTERPRETATION & CONCLUSIONS: The prevalence of ESBL among four study centres varied, and bla(TEM,) bla(OXA-1) and bla(CTXM-15) were the most common genotypes in E. coli and K. pneumoniae isolates in India. The growing carbapenem resistance and emerging colistin resistance warrant the judicious use of these antimicrobials.