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The in vitro efficacy of oxytetracycline against re‐isolated pathogenic Aeromonas hydrophila carrying the cytolytic enterotoxin gene through hybrid catfish, Clarias macrocephalus (Günther, 1864) × Clarias gariepinus (Burchell, 1822) in Thailand
Author(s) -
Juntarut Pongsaton,
Kaewnopparat Sanae,
Faroongsarng Damrongsak,
Chiayvareesajja Sommai
Publication year - 2018
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.13639
Subject(s) - catfish , biology , clarias gariepinus , aeromonas hydrophila , oxytetracycline , microbiology and biotechnology , nile tilapia , aeromonas , enterotoxin , edwardsiella ictaluri , tetracycline , tilapia , veterinary medicine , antibiotics , fishery , bacteria , oreochromis , fish <actinopterygii> , ictalurus , gene , genetics , escherichia coli , medicine , biochemistry
Aeromonas hydrophila is a pathogen infecting farmed hybrid catfish, Clarias macrocephalus (Günther, 1864) × Clarias gariepinus (Burchell, 1822) which incurs substantial economic losses in Thailand. The study aimed at a genetic tracking of A . hydrophila infection and the in vitro assessment of the efficacy of antibiotics against its virulent strains. Five clinical strains from catfishes and Nile tilapia were employed. They were 3‐passage re‐isolated through healthy hybrid catfish and the cytolytic enterotoxin gene ( AHCYTOEN ) of individuals was traced. Each of the re‐isolates at a dose of ~6.67 × 10 5 CFU /g was intraperitoneally injected into ~15 g‐healthy hybrid catfish and their pathogenicity were observed for 7 days. It was found that AHCYTOEN was carried over whereas typical signs of motile aeromonas septicaemia were found in the specimens. The bacterial strains of Nile tilapia origin did not induce mortality but those of catfish origins (80%–100% rate of mortality). The strains were susceptible to the tetracycline antibiotics, and oxytetracycline produced MIC 50 and MBC as low as 0.007–0.031 μg/ ml and 1–8 μg/ ml respectively. As oxytetracycline specifically inhibited pathogenic A. hydrophila in vitro, it is recommended that an appropriate dosage regimen of the drug should be established.