High prevalence of carbapenemase, AmpC β-lactamase and aminoglycoside resistance genes in extended-spectrum β-lactamase-positive uropathogens from Northern India.

OBJECTIVES

This study investigated the occurrence of extended-spectrum β-lactamase (ESBL) genes coexisting with carbapenemase, AmpC and aminoglycoside resistance gene in uropathogens in India.

METHODS

Antimicrobial susceptibility testing was performed by disk diffusion. Antimicrobial resistance genes were detected by multiplex PCR.

RESULTS

Of 1516 consecutive urine samples, 454 (29.9%) showed significant bacteriuria with a single micro-organism, predominantly Escherichia coli (n=343), followed by Klebsiella pneumoniae (n=92), Pseudomonas aeruginosa (n=10) and Proteus mirabilis (n=9). Among the uropathogens, 61 ESBL-producers were identified containing blaCTX-M-15 (n=32), blaCTX-M-15+blaOXA-2 (n=15), blaCTX-M-15+blaOXA-2+blaTEM-1 (n=6), blaOXA-2 (n=5), blaOXA-2+blaSHV-76 (n=1), blaTEM-1+blaSHV-76 (n=1) and blaTEM-1 (n=1). All ESBL genes were located on horizontally transferable plasmids of incompatibility types HI1, I1, FIA+FIB, FIA and Y. Among the 61 ESBL-producers, 59 harboured carbapenemase genes, including blaNDM-5 (n=48), blaNDM-5+blaOXA-48 (n=5), blaNDM-5+blaIMP (n=5) and blaNDM-5+blaIMP+blaVIM (n=1). ESBL-producing uropathogens also harboured 16S rRNA methylase genes, including rmtB (n=9), rmtA (n=4), rmtC (n=1) and armA (n=1). ESBL-positive isolates also contained AmpC genes, including blaCIT (n=8) and blaDHA-1 (n=1). Imipenem and gentamicin had the lowest resistance rates against the uropathogens.

CONCLUSION

This is the first report showing the high prevalence of carbapenemases in ESBL-positive isolates in this area. Regular surveillance for such resistance mechanisms will be useful for health personnel to treat infections by these multidrug-resistant pathogens.