Therapeutic Efficacy of Amoxicillin and Lincomycin Administration Against Streptococcus parauberis in Starry Flounders (Platichthys stellatus)

Abstract

This study evaluated the therapeutic efficacy of amoxicillin (AMX) or lincomycin (LCM) in starry flounders (Platichthys stellatus) infected with Streptococcus parauberis. Seventeen S. parauberis strains isolated from various regions of Korea were tested to determine the minimum inhibitory concentrations (MICs) of AMX and LCM. A representative strain (HFTC0091) was used for the experiments. Following bacterial infection, starry flounders were treated with either oral AMX (40 or 80 mg/kg/d for 7 days) or a single intramuscular (IM) injection of LCM (10 or 20 mg/kg). High-dose treatments with both antibiotics resulted in significantly improved survival rates (96%-100% for AMX and 76%-96% for LCM) compared to nearly 100% mortality in the untreated controls. Serum biochemical analyses (glutamic oxaloacetic transaminase [GOT], glutamic pyruvic transaminase [GPT], and total protein [TP]) showed no significant toxicity; however, GOT and GPT levels were slightly decreased in the LCM-treated group, indicating a potential anti-inflammatory role of LCM, which warrants further investigation. This study demonstrates the effectiveness and safety of AMX and LCM in treating streptococcal infections in starry flounders and highlights the potential of the antibiotics as therapeutic agents in aquaculture. Future studies should investigate whether LCM modulates inflammatory pathways and elucidates the underlying molecular mechanisms in fish.