Ciprofloxacin-resistant Gram-negative isolates from a tertiary care hospital in Eastern India with novel gyrA and parC gene mutations

Abstract

BackgroundExpanded-spectrum quinolones (ciprofloxacin) are highly effective against gram-negative bacteria, but significant resistance to quinolones has been increasingly reported. We sought to evaluate the prevalence of gram-negative ciprofloxacin-resistant isolates (CRIs) from our hospital and their mechanism of action. MethodsGram-negative CRIs were identified as per standard procedures and confirmed using the Ezy MICTM Strip (HiMedia). DNA from 67 CRIs was amplified for the quinolone resistance–determining region (QRDR) and plasmid-mediated quinolone resistance genes. Thirty isolates positive for QRDR DNA were sequenced by Sanger's method to detect mutation. ResultsOf the isolates, 42.5% were found to be CRIs, the majority (74.42%) from inpatient departments, and Escherichia coli (64.19%) was the predominant isolate. Among the CRIs, 24.55% were ESBL producers and 35.29% were multidrug resistant. The polymerase chain reaction results showed the majority were amplified by QRDR target regions of gyrA (35.4%) while 4.61% were amplified for the plasmid-mediated fluoroquinolone resistance region of the qnrB gene. Further sequencing of QRDR-positive genes showed point mutations with amino acid changes at codons Ser83 and Asp87 in the gyrA gene and Ser80, Glu84, and Leu88 positions in the parC gene. ConclusionCiprofloxacin resistance observed in our study was mostly due to point mutations. Hence, strategies for rational use of ciprofloxacin and adherence to the dose and duration of treatment could be helpful to prevent selection and spread of mutant CRIs/strains.