Occurrence of Multiple Antibiotic Resistant Bacteria in Selected Aquaculture Farms of Korea

Abstract

Antibiotics have been used for the control of microbial growth in fish, humans and other animals globally. Due to the continuous application of antibiotics in aquaculture, the levels of antibiotic residues have drastically increased in the aquatic environment for years, which have increased the aquatic bacterial exposure leading to various challenges of antibiotics resistance among bacteria, antibiotic resistant gene transfer among pathogenic and non-pathogenic bacteria strains. Hence, in this study we aim to identify Multiple Antibiotic Resistance (MAR) gene in bacteria isolated from aquatic farms. We have also investigated possible transfer of genes between bacterial strains. We have collected 21 water samples from 4 aquaculture farms in Korea. Bacterial strains in each samples were isolated and tested for antibiotic resistance on Mueller Hinton Agar (MHA) media containing Tetracycline, Kanamycin, Streptomycin, Ampicillin, Vancomycin, Amikacin, Impenem, Gentamicin, Aztreonam, Meropenem, Cefepime, Cefotaxime, Ertapenem and Ceftazidime. As a result, we have isolated 10 bacterial strains with ability to grow in relatively high antibiotic concentrations. Among isolated bacteria, Halomonas alkaliphila strains showed relatively higher Minimum Inhibitory Concentrations (MICs) greater than 32 mg/ml while other isolated bacteria, Pseudomonas segitis, Pseudomonas species and Psychrobacter celer showed MICs of 0.96 mg/ml, 0.24 mg/ml and 0.48 mg/ml, respectively. In this study, we have also investigated transfer of gene aph-6-id in conjugation assay with E. coli. The results clearly indicate that Multiple Antibiotic Resistance bacteria, carrying resistant genes on mobile genetic elements are present in the different aquaculture farms. The development and reserving of antibiotic resistance and the dissemination of the resistance genes among bacteria are likely to increase in aquatic environments due to the continuous application of antibiotics in fish farms.