Bacterial Contamination and Public Health Risks Associated with Aquaculture and Wild-caught Fish in Urban Water Bodies, in Southern Nigeria

Abstract

Background: Fish is an important dietary component in Nigerian riverine communities, but bacterial contamination may constitute a significant food safety and public health concern. Objective: This study evaluated the prevalence and diversity of pathogenic bacteria associated with Clarias gariepinus, Oreochromis niloticus, and Mugil cephalus obtained from creeks, aquaculture ponds, and open markets in Port Harcourt, Rivers State, Nigeria. Methods: Forty-two fish samples, comprising 24 fresh and 18 smoked specimens, were collected from three creeks, three ponds, and three markets. Skin surfaces, skin tissues, gills, and intestines were sampled, yielding 168 specimens. Bacterial isolation was performed using MacConkey, Salmonella-Shigella, and thiosulphate-citrate-bile salts-sucrose (TCBS) agar. Isolates were identified using colony morphology, Gram staining, and standard biochemical tests. Results: Bacterial growth occurred in 163/168 (97.0%) specimens. Thirteen bacterial species were recovered, including Bacillus cereus, Escherichia coli, Klebsiella spp., Proteus spp., Pseudomonas aeruginosa, Salmonella spp., Staphylococcus aureus, Vibrio cholerae, and Vibrio parahaemolyticus. Proteus spp. (17.5%), P. aeruginosa (14.9%), and E. coli (13.2%) predominated. Pond-cultured catfish had the highest bacterial load (36.5 × 10⁵ CFU/g), exceeding the reported recommended limit of 5 × 10⁵ CFU/g. Creek fish contributed 40.4% of isolates, followed by market fish (35.7%). Faecal indicators, including E. coli, Klebsiella spp., and Salmonella spp., indicated possible environmental and handling-related contamination. Conclusion: Fish in Port Harcourt harbour diverse potentially pathogenic bacteria, highlighting foodborne disease risks and the need for improved aquaculture hygiene, environmental sanitation, food handling, surveillance, and consumer education.