Introduction: Co-resistance to quinolones among extended spectrum β[1]lactamase (ESBL)-producing E. coli commonly occurs in clinical settings. Quinolones act on DNA gyrase and DNA topoisomerase enzymes, which are coded by gyrA and parC genes, thus any mutation to the genes may affect the drug effectiveness. The objective of the study was to characterize gyrA and parC genes in quinolone-resistant E. coli isolates and correlated the mutations with their phenotypic resistance. Materials and Methods: Thirty-two quinolone-resistant (QR) and six quinolone-sensitive (QS) ESBL-E. coli isolates were identified by antibiotic susceptibility and minimum inhibitory concentration tests. Bioinformatics analysis were conducted to study any mutations occurred in the genes and generate their codon compositions. Results: All the QR ESBL-E. coli isolates were identified as multidrug-resistant bacteria. A single point mutation in the quinolone resistance-determining region (QRDR) of gyrA, at codon 83, caused the substitution amino acid Ser83Leu. It is associated with a high level of resistance to nalidixic acid. However, double mutations Ser83Leu and Asp87Asn in the same region were significantly linked to higher levels of resistance to ciprofloxacin. Cumulative point mutations in gyrA and/or in parC were also correlated significantly (p<0.05) to increased resistance to ciprofloxacin. Conclusion: Together, the findings showed that the mutations in gyrA and parC genes handled the institution of intrinsic quinolone resistance in the ESBL-E. coli isolates. Thus, vigilant monitoring for emergence of new mutation in resistance genes may give an insight into dissemination of QR ESBL-E. coli in a particular region.

Introduction: Quinolone resistance and extended spectrum beta lactamase production has increased in  E.coli  and considered a serious problem worldwide. It is worth to monitor resistance mechanism in  E.coli  to provide guidance for optimizing antimicrobial treatments,control and spread of resistance. The objective of this study was to molecularly characterize  gyrA, parC  genes and  plasmid mediated  qepA  efflux pump gene, in QR-ESBL  E. coli  isolates obtained from patients in HTAA, Kuantan. The antibiotic susceptibility profile was also studied. Materials and Method: 32 QR-ESBL and six quinolone-susceptible  E. coli  isolates from  September 30 November,2018) included in the study. The isolates were reconfirmed with known phenotypic tests and antibiotic susceptibility test was performed. PCR and DNA sequencing were performed for the identification of mutations in quinolone resistance determining region. Result: Resistance to ampicillin, tetracycline, nalidixic acid was (100%) followed by cefotaxime (96.9%), ciprofloxacin (78.1%) trimethoprim sulfamethoxazole (75%), ceftazidime (56.3%), cefepime (43.8%) and gentamycin (25%). None of the isolates was resistant to piperacillin-tazobactam, amikacin, imipenem, meropenem, ertapenem, and colistin. PCR successfully amplified the  gyrA  and  parC  genes, however,  qepA  gene was not detected by PCR in the isolates. Majority of the isolates had point mutation in (QRDR) of GyrA at codons 83 and 87 and in ParC at codons 80 and 84. Two isolates had mutations outside of QRDR at codons 144 and 167 in ParC. Strong positive correlation was found between MIC levels of ciprofloxacin and the number of resistance mutations. Sequencing of 6 (QS-ESBL)  E. coli  revealed absence of resistance mutations.  Conclusion: Quinolone resistance in the isolates was mainly due to mutations in  gyrA, ParC  genes. Acquisition of multidrug resistance genes through innate gene mutations and mobile genetic elements contribute to the emergence of (MDR). This study reinforces the importance of being vigilant in utilizing molecular techniques to monitor for emergence of resistance genes in different locations.