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 bla_CTX-M-15 (n=32), bla_CTX-M-15+bla_OXA-2 (n=15), bla_CTX-M-15+bla_OXA-2+bla_TEM-1 (n=6), bla_OXA-2 (n=5), bla_OXA-2+bla_SHV-76 (n=1), bla_TEM-1+bla_SHV-76 (n=1) and bla_TEM-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 bla_NDM-5 (n=48), bla_NDM-5+bla_OXA-48 (n=5), bla_NDM-5+bla_IMP (n=5) and bla_NDM-5+bla_IMP+bla_VIM (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 bla_CIT (n=8) and bla_DHA-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.