Bacterial contamination levels in fresh fish fillets sold in Lusaka district, Zambia.

Zambia has seen rapid growth in aquaculture, with fish increasingly becoming a source of emerging bacterial zoonotic diseases. This cross-sectional study assessed the levels of bacterial contamination in 132 fresh fish fillets, consisting of 69 hake and 63 tilapia sold in Lusaka District, Zambia, addressing the research gap in local fish contamination and antimicrobial resistance. The isolates were identified using their morphological
characteristics and conventional biochemical tests. The antibiotic susceptibility of selected bacteria was determined by the Kirby–Bauer disc diffusion method. Total viable count (TVC) and faecal coliform presence revealed that 31% of the samples exceeded the TVC limit, and 45% exhibited faecal coliforms. While hake fillets had no faecal contamination, 93% of tilapia fillets were contaminated, with only four samples testing negative for faecal coliforms. Escherichia coli was the predominant bacterium (53.8%), followed by Klebsiella pneumoniae (46.2%), and other species such as Vibrio
parahaemolyticus and Staphylococcus aureus. Antimicrobial susceptibility testing (AST) revealed chloramphenicol’s broad-spectrum efficacy against most bacteria, while penicillin resistance was noted in Staphylococcus and Serratia species. Ciprofloxacin and doxycycline were mostly effective, though one E. coli strain showed resistance. The high levels of contamination, especially in tilapia fillets, pose significant health risks, particularly to vulnerable populations such as children, the elderly, and immunocompromised individuals. While the exact quantity required for negative health
effects varies based on bacterial load and individual susceptibility, ingestion of contaminated fish could lead to gastrointestinal illness or more severe outcomes. The study highlights the need for better farming practices, improved food safety standards, and stricter regulatory enforcement to mitigate microbial contamination in fish products. Public awareness on proper fish handling and cooking is also crucial to minimize health risks.