Detection and antibiogram of Edwardsiella tarda from Oreochromis niloticus (Tilapia) obtained from selected farms in Ibadan, Nigeria

Edwardsiellosis caused by Edwardsiella tarda is a septicemic bacterial disease responsible for 5-70% mortalities and prevalence up-to 70% in freshwater fishes. Although rarely associated with human infections, Edwardsiella tarda has been found to cause gastroenteritis, soft tissue infection, liver abscess, tubo-ovarian abscess, and mycotic aneurysm mostly in immunocompromised humans. This study investigated the prevalence and antibiogram of E. tarda isolated from Oreochromis niloticus obtained from selected farms in Ibadan, Nigeria. A total of 156 samples consisting: gills, intestines and skins were collected from 52 O. niloticus from Egbeda-(A), Ido-(B), Ibadan: North-East-(C) and North-West-(D) for bacteriological analysis. E. tarda Isolation, identification, and antibiogram were performed using standard methods. Data were analyzed using Chi-Square. An overall prevalence of 62.5% was observed for E. tarda with 87.5%, 62.5% and 50.0% for gills, intestine and skin samples, respectively, whilst overall location prevalence was observed as 100.0%-(A), 50.0%-(B), 66.6%-(C) and 50.0%-(D). Isolates exhibited resistance patterns comprising; 100.0%-(Ceftazidime-(CPZ), Cefuroxime-(CRX) and Meropenem-(MEM)), 91.7%-Cefotaxime-(CTX), 83.3%-(Tetracycline-(TET)), 50.0%-(Cotrimoxazole-(COT)), 33.3% (Ceftriaxone-(CTR) and Gentamicin-(GEN)), 25.0%-(Chloramphenicol-(CHL)), 16.7%-Amikacin-(AMK) and 8.3%-(Ciprofloxacin-(CIP)). Multi-drug resistance pattern: CRX-CFZ-MEM-(100%), CRX-CTR-CTX-CFZ-MEM-(83.3%), CRX-CTR-CTX-CFZ-MEM-TET-(66.7%), CRX-CTR-CTX-CFZ-MEM-TET-COT-(58.3%) and CRX-CTR-CTX-CFZ-MEM-TET-COT-GEN-(8.3%) was observed. Isolation and identification of E. tarda from O. niloticus confirm its presence in Ibadan and affirms that O. niloticus harbors, and could serve as a source of infection to humans. The antimicrobial resistance patterns of isolates to antibiotics indicate misuse in aquaculture and indiscriminate disposal of antibiotics into aquatic environments. This suggests risks of transmission of infectious agents to humans and the probable spread of resistant pathogens to humans from the environment.