Occurrence, prevalence and genetic environment of CTX-M -lactamases in Enterobacteriaceae from Indian hospitals

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Abstract
Objectives: To determine occurrence, prevalence and CTX-M genotypes produced by Enterobacteriaceae from clinical samples from three geographically distant Indian hospitals and to detect linkage of IS26 with blaCTX-M and map its precise insertion position. Methods: A total of 130, non-duplicate Escherichia coli and Klebsiella pneumoniae resistant to a third-generation cephalosporin (3GC) from three Indian centres were screened for extended-spectrum β-lactamase (ESBL) production using phenotypic detection methods. All isolates were screened for blaCTX-M using multiplex PCR. Precise CTX-M genotype was identified using reverse-line hybridization. All CTX-M-producing isolates were screened for linkage of IS26 with blaCTX-M. DNA sequencing was used to map the exact insertion position of this mobile element. Results: Ninety-five of 130 3GC-resistant (73%) (73% of total E. coli, 72% of total K. pneumoniae) isolates were found to carry blaCTX-M-15. No other CTX-M genotype was detected. IS26 linkage with blaCTX-M-15 was detected in 31% of isolates carrying blaCTX-M-15. DNA sequencing revealed variable insertion of this mobile element within tnpA of ISEcp1. RAPD–PCR typing demonstrated great diversity in isolates carrying blaCTX-M-15; no predominant clone was identified. Conclusions: In contrast with other studies where greater diversity exists, CTX-M-15 was the only CTX-M ESBL produced in this Indian collection of unrelated E. coli and K. pneumoniae. This is the first systematic survey report from India detecting CTX-M-type β-lactamases This is also the first report indicating such high mobility/diversity of insertion of IS26 in close association with blaCTX-M in a single bacterial collection.

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