Characterization of bla_CTX-M sequences of Indian origin and thirteen uropathogenic Escherichia coli isolates resistant to multiple antibiotics

ESBL-producing isolates of the Enterobacteriaceae occur throughout the world. The objectives of this study were to characterize uropathogenic Escherichia coli isolated at a tertiary care hospital in southern India, and shed light on bla_CTX-M sequences of Indian origin.

A cohort of 13 urinary isolates of E. coli (obtained from patients at the Sri Sathya Sai Institute of Higher Medical Sciences, Prasanthigram, Andhra Pradesh, India) were characterized and found to be resistant to multiple antibiotics, including extended-spectrum cephalosporins. All 13 isolates contained bla_CTX-M-15, and many of them transferred this genotype to at least one laboratory strain of E. coli after conjugation. Analyses of bla_CTX-M-15 sequences (n = 141) of Indian origin showed that > 85% of them were obtained from bacteria not associated with the urinary tract, and that E. coli isolates account for majority of all bla_CTX-M-15-carrying bacteria reported from India. Other types of bla_CTX-M appear to be rare in India, since only six such sequences were reported as of July 2015. The results indicate that 'selection pressure' exerted by extended-spectrum cephalosporins may have stabilized the bla_CTX-M-15 genotype among E. coli in India. The rarity of other bla_CTX-M suggests that they lack the survival advantage that bla_CTX-M-15 may have.