Microbial Diversity Of Economically Important Unprocessed Freshwater Fishes Sold At The Medina Coura Market In Bamako, Mali

Abstract

Around the world, millions of people depend on fish for its high protein content, supply of micronutrients and added health benefits. Fish is extremely perishable; its quality changes very quickly after capture unless it is kept cold. Failure to comply with good preservation practices favors the risk of deterioration in market quality and safety, which may lead to foodborne illness. The purpose of this study was to determine the microbial diversity of fresh water fish and evaluate the food safety knowledge and practices of stakeholders of freshwater fish along selected fish value chains in Mali. A structured face-to-face questionnaire on food safety knowledge and practices was designed and administered to 247 respondents comprising 130 fish sellers and 117 fishermen between November 2018 and February 2019. Samples of three fresh water fish species (Lates niloticus, Clarias anguillaris and Oreochromis niloticus) were taken during cold and hot seasons in four fish production areas and at specific points (capture, landing and selling points) in the selected value chains (Niger Central Delta in Mopti, Selingue, Manantali, Markala) and from the Central fish market (Medina Coura market) using standard protocols for microbial analysis.Water samples at capture areas and swabs of fish containers at each of the landing points were also collected for analysis. The following assessments were carried out: enumeration for Aerobic Plate Count (APCs), Total Coliform counts (TCs), Fecal Coliform counts (FCs), and Spores of Sulphite Reducing Bacteria (SRB), Staphylococcus aureus and prevalence of Salmonella spp. were also determined. Bacterial isolates were identified using biochemical tests (catalase oxidase, API 20E and 20NE). Parasitic infestations of 120 specimens of three freshwater fish species, comprising Lates niloticus (44), Clarias anguillaris (40) and Oreochromis niloticus (36) sold at the Medina Coura market in Mali, were also investigated. The results of the questionnaire survey indicated that respondents had a good level of food safety knowledge but poor food hygiene practices. Most of the respondents had received no formal education in food safety. It is, therefore, important to put in place a good public health management strategy for food sales services, which will give stakeholders in the fish value chain the knowledge and skills necessary to provide hygienic and safe sales services. Microbial growth was observed in all of the fish species tested. APC ranged from 5.08 to 7.64 Log10 CFU.g-1, TC ranged from 4.11 to 7.62 Log10 CFU.g-1, FC ranged from 3.64 to 7.5 Log10 CFU.g-1 and all had 100% higher counts than the national standard. About 12.7% (17/134) of the samples recorded Sulphite Reducing Bacteria, 20.1% (27/134) had Staphylococcus aureus, and 93.3 % (125/134) Salmonella spp.. Three species of parasites were detected, namely, Salmincola edwardsii (crustacea) at the gills, and Philonema sp. and Raphidascaris sp. (nematodes) in the abdominal cavity. An overall prevalence of 10% (12/120) parasitic infestation was observed. The study showed that prevalence of parasitic infestation during the cold season was 5.2% and the hot season was 14.5%. The highest prevalence of infestation was observed in Oreochromis niloticus (16.7%) followed by Lates niloticus (9.1%) and Clarias anguillaris (5.0%). A total of 360 isolates (188 in the cold season and 172 in the hot season) were characterized and identified as 24 species of bacteria belonging to 15 families. This study is an important contribution to the knowledge of the bacterial and parasitological flora of fish along the value chain sold on the Medina Coura Market, and contributes, to my knowledge as the first attempt to evaluate the microbiological quality of these freshwater fish along the fish value chains.