The Thai Journal of Veterinary Medicine


Thirty bacterial isolates were derived from ornamental fish patients (n=30) of the Veterinary Medical Aquatic Animal Research Center (VMARC), Faculty of Veterinary Science, Chulalongkorn University. The isolated bacterial strains were identified by using commercial biochemical identification kit (API Kits, bioMerieux® SA France). The antibiotics susceptibility testing was performed by disc diffusion method, using 24 types of antibiotic discs (OXOID, Oxoid Ltd, UK). The result showed that the majority of the isolated bacteria was Aeromonas hydrophila (27/30). In the A. hydrophila susceptibility study, 66.30% of bacteria were antibiotic resistant, 9.35% were intermediately sensitive and 24.35% were sensitive strains against the tested antibiotics. Chloramphenicol showed the highest efficacy against the bacterial strains tested. Other effective antibiotics included sulphamethoxazole-trimetroprim and amikacin. 100% of the isolated bacteria showed resistance to metronidazole, 92.31 were resistant to penicillin and amoxicillin. It is noticeable that there were large numbers of antibiotic resistance fish pathogenic bacteria in ornamental fish, which indicated that the risk of ineffective antibiotic treatment without laboratory susceptibility test in sick fish would be at least 75.65% in doubt.

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