Aquaculture products can harbor pathogenic bacteria which are part of the natural microflora of the environment. A study was conducted aiming at the isolation of human pathogenic bacteria in gills, intestines, mouth and the skin of apparently healthy fish, the Oreochromis niloticus L., from Lake Chivero. Bacterial pathogens associated with fish can be transmitted to human beings from fish used as food or by handling the fish causing human diseases. Differentiation and characterization of various isolates was based on their growth characteristics on specific culture media (biochemical and gram staining reactions). The results showed that the fish is contaminated with Pseudomonas flouresens, Listeria monocytogenes, Esterichia .coli, Pseudomonas capacia, Proteus vulgaris, and Klebsiella oxytoca. This might be a result of untreated sewage disposed from several settlements and industrial areas. The antibiotic profiling done showed that gentamycin proved to be a good antibiotic against all bacteria isolated followed by kanamycin. Proteus vulgaris showed resistance to neomycin whilst Pseudomonas capacia showed resistance to kanamycin. All the bacterial species which were isolated from the fish were also present in the initial water samples collected. The isolation of enteric bacteria in fish serves as indicator organisms of faecal contamination and or water pollution. Their presence also represents a potential hazard to humans. The mean bacterial load of the isolates of 2.098 x106 CFU/ml was found to be markedly higher than the recommended public health and standard value of 5.0 x 105 CFU/ml which has been adopted by many countries.
Keywords: Isolation, faecal contamination, Salmonella typhi, Pseudomonas aeruginosa, antibiotic resistance