Ecological Diversity of Migratory Birds and Their Associated Bacterial Species in South Korea: A Preliminary Study Including Antimicrobial Resistance Profiles

Migratory birds travel long distances and interact with diverse environments, making them potential reservoirs and disseminators of antimicrobial-resistant bacteria. This study investigated the species distribution of migratory birds, bacterial isolates from bird internal organs, and the corresponding antimicrobial resistance (AMR) profiles in South Korea. A total of 35 bird carcasses representing 20 species were collected from five major stopover sites on the Sinan-gun islands along the East Asian-Australasian Flyway. More than half of the sampled birds belonged to the genus <i>Emberiza</i>, reflecting the prevalence of small migratory passerines in coastal habitats. From these carcasses, 54 bacterial isolates belonging to 24 species were identified, including <i>Enterococcus</i> spp., coliforms such as <i>Enterobacter</i> spp. and <i>Escherichia coli</i>, and opportunistic pathogens including <i>Bacillus</i> spp., <i>Staphylococcus</i> spp., and <i>Serratia</i> spp. Antimicrobial susceptibility testing revealed that 18 isolates (33.3%) were multidrug-resistant (MDR). <i>Enterococcus</i> isolates displayed high resistance to tigecycline and daptomycin, and two vancomycin-resistant strains were identified. Coliform isolates were resistant to third- and fourth-generation cephalosporins, carbapenems, and colistin. The two <i>E. coli</i> strains exhibited concurrent carbapenem-colistin resistance, posing a significant public health concern. These findings provide the first organ-level AMR dataset for migratory birds in South Korea and highlight the potential role of small passerines as ecological sentinels of environmental contamination. The detection of MDR strains underscores the need to integrate wildlife surveillance into One Health strategies for AMR monitoring.