Comparison of Antibiotic Resistance Patterns of Fecal-indicator Bacteria Isolated from Fish Farms and Adjacent Inland Pollution Sources in the Southern Coast of Korea

This study investigated the contamination levels and antibiotic resistance characteristics of fecal-indicator bacteria isolated from fish farms and adjacent inland pollution sources on the southern coast of Korea. From July to November 2023, samples of seawater and fish (black rockfish and red sea bream), stream water near the aquatic farms, and livestock manures (chicken and cattle) were collected. A total of 251 bacteria were isolated, of which 197 were Escherichia coli and 54 were Enterococcus spp. The highest contamination levels were found in livestock manures and upstream. In antibiotic resistance tests, E. coli isolated from chicken manures showed high resistance to ciprofloxacin, tetracycline, chloramphenicol, ampicillin, and trimethoprim/sulfamethoxazole. Similar resistance patterns were observed in adjacent stream water and aquatic fish farms. Multiple antimicrobial resistance bacteria (MARB) was significant, with 12.6% of E. coli isolated from livestock manures having a MAR index greater than 0.2. These results highlight the potential of terrestrial sources of contamination to have a significant impact on the sanitary conditions of marine aquaculture farms and the spread of antibiotic-resistant bacteria, and suggest the need for effective management strategies to prevent the spread of antibiotic-resistant bacteria.