Microbiological Quality and Prevalence of Bacterial and Fungal Contaminants in African Catfish (Clarias Gariepinus) From Ajiwa Dam, Katsina State, Nigeria

Abstract

The microbiological quality of fish is an important consideration in food safety because contamination may occur from the aquatic environment or during harvesting, transportation and handling. This study investigated bacterial and fungal contaminants associated with African catfish (Clarias gariepinus) obtained from Ajiwa Dam, Batagarawa Local Government Area, Katsina State, Nigeria. Fish were collected from three landing sites: Gajeren Giwa, Kwatani and Masabo during four weekly sampling visits in May. Fillet portions were aseptically processed, serially diluted to 10⁻⁴ and 10⁻⁵, inoculated on culture media, and incubated for microbial enumeration. Bacterial isolates were characterized using Gram staining and conventional biochemical tests. Five bacterial taxa and seven fungal taxa were recovered. Among the nine bacterial isolates, Escherichia coli was most frequent (33.3%), followed by Bacillus spp. and Staphylococcus aureus (22.2% each), while Klebsiella spp. and Micrococcus spp. each accounted for 11.1%. Among nine fungal isolates, Aspergillus niger and Saccharomyces cerevisiae were most frequent (22.2% each), whereas A. fumigatus, Penicillium spp., Fonsecaea spp., Cladosporium spp. and Fusarium oxysporum each accounted for 11.1%. Reported bacterial plate counts ranged from 36 to 198 CFU/g and fungal counts from 21 to 84 CFU/g across the evaluated dilutions. The microbial profile is consistent with possible environmental and/or post-harvest contamination; however, the present design cannot identify the specific contamination source. Improved hygienic handling and periodic microbiological monitoring of fish and the dam environment are therefore recommended.