Effects of efflux pump inhibitors on the amphenicols resistance of Vibrio strains isolated from marine aquaculture

This study was conducted to determine the role of efflux pump inhibitors in amphenicols resistance of Vibrio species from mariculture. A total of 41 intermediate/high-level florfenicol-resistant Vibrio isolates were tested, including V. parahaemolyticus (14), V. alginolyticus (17), V. harveyi (8), and V. vulnificus (2). To investigate the effect of efflux pump on amphenicols resistance, minimal inhibitory concentrations of chloramphenicol and florfenicol with/without efflux pump inhibitors were determined using the agar dilution method. NMP, reserpine, CCCP and PAβN were used as efflux pump inhibitors in this study. PCR amplication method was used to detect the efflux pump genes and integron-related genes. The results showed that 39 strains and 11 strains were resistant to florfenicol and chloramphenicol, respectively. As is shown, 100% (41/41) of the 41 Vibrio isolates tested were detected positive for amphenicols efflux pump genes floR, but only 17.1% (7/41) for cmlA gene, and pexA, fexA, fexB and optrA could not be detected. Furthermore, Int1, SXT, and ISCR1 were found in 46.3% (19/41), 46.3% (19/41), and 63.4% (26/41) of the 41 Vibrio isolates tested, respectively. Antibiotic susceptibility testing suggested that CCCP was an effective efflux pump inhibitor in the treatment for the amphenicol resistance of Vibrio species. The prevalence of amphenicol resistance, efflux pump genes and integron-related elements in Vibrio sp. derived from marine aquaculture in China was observed and was likely due to the extensive use of amphencols. The use of efflux pumb inhibitors, e.g. CCCP, might be an effective tool to control the amphenicol resistance in Vibrio species.