Antibiotic Susceptibility of Non-Cholera Vibrios Isolated from Farmed and Wild Marine Fish (Argyrosomus japonicus), Implications for Public Health

This study aimed to evaluate the antibiogram and antibiotic resistance genes (ARGs) of Vibrio isolates recovered from a marine fish (Argyrosomus japonicus) and water samples from two commercial dusky kob aquaculture farms and the Kariega estuary, South Africa, and to evaluate these findings for their public health implications. A total of 277 molecularly confirmed Vibrio isolates consisting of 126 Vibrio fluvialis, 45 Vibrio vulnificus, 30 Vibrio Parahaemolyticus, and 76 vibrios belonging to species of the genus other than Vibrio cholerae were subjected to susceptibility testing to 15 antibiotics by the disc diffusion method. Multiple antibiotic resistance index (MARI) was used to determine the antibiotic resistance-associated health risk, while polymerase chain reaction was used to evaluate the presence of 14 ARGs for nonsusceptible strains. Highest resistances were recorded to amoxicillin (76.2%), ampicillin (67.5%), erythromycin (38.3%), and doxycycline (35.0%), while susceptibilities were highest to gentamicin (100%), followed by norfloxacin (97.8%), florfenicol (90.3%), tetracycline (87.7%), and chloramphenicol (87.4%). We recorded a 58.5% multidrug resistance (resistance to 2 antimicrobial classes). MARI did not vary significantly between sites (p>0.05); however, values of >0.2 were recorded in 40% (108/277) of all strains tested. ARG markers, ampC, blaOXA, tetA, tetM, dfr1, sul1, sul2, ermB, nptII, strA, and SXT integrase, were detected in one or more strains with ermB (82.5%), sul2 (53.8%), strA (44%), dfr1 (42.3%), and tetM (38.3%) being the most abundant. Healthy marine finfish (dusky kob) and their environment can serve as reservoirs for antibiotic resistant vibrios and ARGs, which could be disseminated to humans and other susceptible bacteria and this therefore becomes a public health concern.