Investigation of gyrA and parC mutations and the prevalence of plasmid-mediated quinolone resistance genes in Klebsiella pneumoniae clinical isolates

Abstract

BACKGROUND: The emergence of fluoroquinolone resistance in clinical isolates of Klebsiella pneumoniae is a growing concern. To investigate the mechanisms behind this resistance, we studied a total of 215 K. pneumoniae isolates from hospitals in Bushehr province, Iran, collected between 2017 and 2019. Antimicrobial susceptibility test for fluoroquinolones was determined. The presence of plasmid mediated quinolone resistance (PMQR) and mutations in quinolone resistance-determining region (QRDR) of gyrA and parC genes in ciprofloxacin-resistant K. pneumoniae isolates were identified by PCR and sequencing. RESULTS: Out of 215 K. pneumoniae isolates, 40 were resistant to ciprofloxacin as determined by E-test method. PCR analysis revealed that among these ciprofloxacin-resistant isolates, 13 (32.5%), 7 (17.5%), 40 (100%), and 25 (62.5%) isolates harbored qnrB, qnrS, oqxA and aac(6')-Ib-cr genes, respectively. Mutation analysis of gyrA and parC genes showed that 35 (87.5%) and 34 (85%) of the ciprofloxacin-resistant isolates had mutations in these genes, respectively. The most frequent mutations were observed in codon 83 of gyrA and codon 80 of parC gene. Single gyrA substitution, Ser83→ Ile and Asp87→Gly, and double substitutions, Ser83→Phe plus Asp87→Ala, Ser83→Tyr plus Asp87→Ala, Ser83→Ile plus Asp87→Tyr, Ser83→Phe plus Asp87→Asn and Ser83→Ile plus Asp87→Gly were detected. In addition, Ser80→Ile and Glu84→Lys single substitution were found in parC gene. CONCLUSIONS: Our results indicated that 90% of isolates have at least one mutation in QRDR of gyrA orparC genes, thus the frequency of mutations was very significant and alarming in our region.