Consumer health risk assessment of coliforms and associated bacterial pathogens in Nile tilapia (Oreochromis niloticus) from Lake Hawassa, Ethiopia
Keywords:
Coliforms, Health risk, Nile tilapia (Oreochromis niloticus) pathogenic bacteria, Lake HawassaAbstract
Fish is the most essential source of protein for humans and has high nutritional value. However, fish and fishery products have been documented as carriers of food-borne bacterial pathogens, and the presences of coliforms are used as indicator for the possible presence of these pathogens. Therefore, this study aimed to evaluate the loads of coliform and the prevalence of potential bacterial pathogens in Nile tilapia (O. niloticus), and the health risk to consumers from Lake Hawassa, Ethiopia. Freshly-caught O. niloticus (n=100) intestine, skin, muscle, and gills tissues were sampled. Out of the 400 samples, bacteria were isolated and identified from 293(73.25%) samples, and coliform loads were detected from 34(34%) muscle and intestine samples on suitable culture media. Bacterial pathogens belonging to 18 genera such as Acinetobacter (5.12%), Aeromonas (12.97%), Bacillus (10.92%), Citrobacter (2.05%), Edwardsiella (4.10%), Enterobacter (5.80%), Enterococcus (9.89%), Escherichia (6.48%), Klebsiella (1.36%), Morganella (5.80%), Proteus (4.44%), Providencia (5.80%), Pseudomonas (9.89%), Salmonella (4.10%), Serratia (1.71%), Shigella (3.07%) and Stenotrophomonas (6.48%) were isolated and identified. The highest number of bacteria (36.86%) was isolated from the intestinal sample, followed by the gills (25.94%), skins (23.89%), and muscle (13.31%), with statistically significant difference (p<0.0001). Overall, the least identified bacterium was Klebsiella (1.36%) followed by Serratia (1.71%), with statistically significant difference (p<0.05). The densities of fecal coliform (E. coli) (CFU/g) found in the intestines (4.21×105 CFU/g) were found to be higher than in the muscle samples (3.6×104 CFU/g) of O. niloticus. However, the densities of non-fecal coliform (CFU/g) found in the intestine (4.3×104 CFU/g) were found to be lower than the muscle (3.1×105 CFU/g) of O. niloticus samples. The potential bacterial pathogens isolated and identified are contaminants of fish in the study area, and could represent a risk to the health of consumers. The total coliform loads indicate that they were above the recommended level of the Centre for Food Safety standards. It was concluded that poor hygienic water conditions and overloading allowed the opportunistic bacterial contaminations to succeed, which caused a serious threat to consumers’ health.
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