In vitro antibiotic susceptibility of bacteria isolated from EUS-affected fishes in India

AIMS: Twelve antibiotics were evaluated for in vitro sensitivity against 16 bacterial strains isolated from surface lesions of fishes affected with epizootic ulcerative syndrome (EUS). METHODS AND RESULTS: Disc diffusion assay in Mueller-Hinton agar showed that the pseudomonads and aeromonads were mainly resistant to penicillin, ampicillin and erythromycin. Additionally, some were resistant to gentamycin and amoxycillin. However, resistance towards antibiotics previously recommended for EUS treatment, such as oxytetracycline and chloramphenicol, was not observed. Four aeromonads and two pseudomonads were found to induce ulcers when injected intramuscularly in healthy Anabas testudineus. CONCLUSIONS: All six pathogenic isolates were sensitive towards oxytetracycline, chloramphenicol and nalidixic acid. Oxytetracycline seems to be an effective antibiotic, and further investigations to determine the mode of treatment and dose appear to be worthwhile.