국내 양식 강도다리(Platichthys stellatus)에서 분리된 Streptococcus parauberis의 mRPA를 이용한 동정 및 항생제 내성 유전자 분석 = Identification of Streptococcus parauberis from cultured starry flounder (Platichthys stellatus) in Korea using multiplex recombinase polymerase amplification and analysis of antibiotic resistance genes

다국어 초록 (Multilingual Abstract)

Recent increases in streptococcal infections in marine aquaculture have raised concerns regarding the epidemiological characteristics and antimicrobial resistance in fish. This study investigated the serotype distribution and resistance gene profiles of Streptococcus parauberis isolates from cultured fish. Three strains (25gp01, 25sj02 and 25gp03) isolated from starry flounder (Platichthys stellatus) in Pohang, Korea, in 2025 were identified as serotype Ia using multiplex recombinase polymerase amplification (mRPA). In addition, 21 previously isolated strains collected from cultured fish between 1999 and 2023 were included to analyze serotyping and the presence of tetracycline (tet) and macrolide (erm) resistance genes. Among the previously isolated strains, serotype II predominated between 1999 and 2007 (70%, 7/10), while serotype Ia predominated between 2020 and 2023 (63.6%, 7/11). Furthermore, resistance gene profiles differed according to serotype. All serotype Ia strains harbored tet(S), whereas all serotype II strains harbored tet(M). The erm(B) gene was detected in 53.8% (7/13) of the serotype Ia strains but not in any serotype II strains (0/7). These findings suggest the possibility of temporal shifts in the serotype distribution and resistance gene profiles of S. parauberis isolates from cultured fish in Korea.