An unusually high level of quinolone resistance associated with type II topoisomerase mutations in quinolone resistance-determining regions of Aeromonas caviae isolated from diarrhoeal patients

Abstract

We examined 158 strains belonging to different Aeromonas species isolated from hospitalized acute diarrhoea cases for susceptibility to quinolones. Compared to other species, a high percentage of the A. caviae strains were resistant to ciprofloxacin and norfloxacin. Based on MIC values, 6 A. caviae strains were selected and the nucleotide sequences for the quinolone-resistant-determining regions (QRDRs) of gyrA, gyrB and parC genes were analysed. In resistant strains, double mutations (Ser 83→Ile and Asp 87→Asn) and a single mutation (Ser 80→Ile) were detected in the QRDR of gyrA and parC, respectively.