Antibiotic use in aquaculture contributes to antimicrobial resistance in bacteria from aquaculture sources worldwide. Vibrio cholerae and Vibrio parahaemolyticus are commonly reported zoonotic bacterial pathogens of fish. However, information on Vibrio’s prevalence and antibiotic resistance patterns in Nigerian aquaculture is limited. Understanding the prevalence and antibiogram of Vibrio cholerae and Vibrio parahaemolyticus in cultured fish is essential for assessing human health risks and developing effective mitigating strategies against these risks in aquaculture practices.
A total of eighty-four cultured catfish were collected directly from fish farms from four actively selected regions in Ibadan, Oyo state. Liver, kidney, spleen, and muscle were collected from sampled fish and processed for microbiological analysis at the Food Safety Laboratory of the Department of Veterinary Public Health and Preventive Medicine, Faculty of Veterinary Medicine, University of Ibadan, Ibadan. Sampled organs were enriched in buffered peptone water and incubated at 30℃ for 24 hours. The enriched organs were then streaked on Thiosulfate Citrate-Bilesalts Sucrose Agar (Millipore®, Germany), and incubated at 30℃ for 24 hours while growth was observed after 24 hours. The isolates were then subjected to biochemical tests and antibiotic sensitivity tests.
The percentage prevalence of Vibrio cholerae (45.7%) was higher than that of Vibrio parahaemolyticus (23.3%) isolation rate was 68 out of 420; (23.3%). The prevalence of the Vibrio isolates in the regions was: Ido (18%/20%), Lagelu (80%/2.9%), Akinyele (26.7%/5.3%), and Egbeda (30%/32.3%) respectively. Of interest, is the prevalence of both Vibrios in the muscle of the sample fish across the four selected regions. Vibrio cholerae and Vibrio parahaemolyticus were both resistant to Amoxicillin-Clavulanate (100%), Cefotaxine (100%), and Cefuroxime (100), Imipenem (92%/80%) and Nitrofurantoin (88%/80) respectively. They were both susceptible to Gentamycin (76%; 70%), Ofloxacin (60%; 60%) Ceftriaxone (88%; 50%), and Levofloxacin (76%; 80%) respectively. The multiple antibiotic-resistant index of the isolated Vibrio cholerae ranges between 0.33 and 0.78 while that Vibrio parahaemolyticus ranges between 0.44 and 0.78.
The presence of multi-drug resistant Vibrio cholerae and Vibrio parahaemolyticus in table-sized African catfish raised in the active aquaculture regions is an implication of the unwholesomeness of the fish and a concern for fish food safety since catfish is the commonest of the farmed fish in Nigeria and readily available in all fish markets. Therefore, aquaculture biosecurity measures and practising of best management practices should be adopted while regulations on indiscriminate discharge of untreated effluents from industries, hospitals, and households into the waterbodies should implemented.