A possible mechanism of quinolone resistance in Vibrio anguillarum

To study a possible quinolone resistance mechanism in Vibrio anguillarum, we examined gyrA and parC mutations among the oxolinic acid-resistant strains and laboratory-derived mutants. One point mutation only in the quinolone resistance-determining region (QRDR) of the gyrA gene was detected in one strain isolated from ayu Plecoglossus altivelis and laboratory-derived mutants with low-level resistance. On the other hand, point mutations in both the gyrA and parC QRDRs were detected in one strain isolated from ayu and a laboratory-derived mutant with high-level resistance. These results suggest that as in other Gram-negative bacteria GyrA and ParC are the primary and secondary targets, respectively, of quinolone in V. anguillarum.