Microbiological Safety of Fresh Tilapia (Oreochromis niloticus) from Kenyan Fresh Water Fish Value Chains

Abstract

This study evaluated the microbiological safety of fresh Nile tilapia (Oreochromis niloticus) from Kenyan fresh water fish value chains. One hundred seventy-six fish samples were analyzed. The microbial counts of hygiene indicators, total viable aerobic count (TVC), total coliforms, and fecal coliforms isolated by using culture techniques were enumerated, and microbial pathogens present in the fish samples were identified and characterized by using molecular methods. The diversity of bacterial isolates was determined by using the Shannon-Weaver diversity index. The mean of TVC in the samples was 4.44 log CFU/g. A comparison with the European Commission and International Commission on Microbiological Specifications for Foods standards showed two fish samples had counts above the 5.00 log CFU/g limit for TVC, and all the fish samples had total coliform and fecal coliform counts above 2.00 and 1.00 log CFU/g, respectively. Pathogenic strains, including Shiga toxin–producing and enteropathogenic Escherichia coli, Listeria monocytogenes, Yersinia enterocolitica, Klebsiella pneumoniae, and Salmonella enterica, were identified in the fish samples. The diversity of 1,608 bacterial isolates was higher in semiregulated chains than unregulated chains. The diversity was also high at the retail stage of the fish value chain. In conclusion, fresh Nile tilapia samples were above some of the set food safety standards and may be a source of foodborne pathogens. Further microbial risk assessment for detected pathogens is recommended to further support public health protection, taking into account growth, inactivation through cooking, processing, survival, and consumption.

Assessment of antibiotics sensitivity of microbial isolates from fish hatcheries

“…The total viable counts (TVC) observed in this study was lower compared to the findings of Adedeji et al (2012), Hilary et al (2018) and Ogunleye et al (2021). Bacteria of public health importance were isolated, however, the TVC did not exceed 10 5 CFU/g approved by FAO (1979).…”

Asymptomatic Carriage of Listeria monocytogenes by Animals and Humans and Its Impact on the Food Chain

“…After a gavage of L. monocytogenes into the stomachs of live salmon, they were readily cleared without pathologic changes to the animals within three days [ 66 ], and rainbow trout held in fish farms where L. monocytogenes was detected in the water were rarely positive for L. monocytogenes [ 68 ]. A recent study [ 61 ] demonstrated an increase in the L. monocytogenes contamination level in tilapia from capture (1.2%) to the domestic market (5.8%). Taken together, these data suggest that fish may become transient asymptomatic carriers of L. monocytogenes after exposure but are not likely to be long-term spreaders of the pathogen.…”

Bacteria Associated with Fresh-water Aquaculture Tilapia Fish (Oreochromisniloticus) in Suez, Egypt

“…For example, handling tilapia was reported associated with Vibrio vulnificus outbreak in Seattle supermarket [18]. Other foodborne pathogenic bacteria including Salmonella enterica, enteropathogenic Escherichia coli, Listeria monocytogenes, Yersinia enterocolitica, and Klebsiella pneumoniae were identified from fresh Nile tilapia in Kenyan fresh water fish chains [19]. Shigatoxigenic and enteropathogenic Escherichia coli were isolated from farmed tilapia fish (Oreochromis niloticus) in northeast region of Sao Paulo state [20].…”