Assessment of antimicrobial resistance in foodborne bacterial pathogens isolated from Nile tilapia (Oreochromis niloticus) at retail sale points in Kisumu, Kenya

Nile tilapia is a rich source of protein increasingly consumed in Kenya. However, the ability of AMR transfer can cause the rapid establishment of multi drug resistance (MDR) in bacteria from fish thus creating a food-borne risk to human health therefore continuous monitoring of antimicrobial resistance along the food chain is essential. This study aimed to assess the prevalence and antimicrobial resistance patterns, of bacteria isolated from fresh Nile tilapia obtained from retail markets in Kisumu, Kenya.

A total of 68 fish samples, with an average weight of 300 g and mean body length of 23 cm, were randomly collected, analyzed for the presence of Proteus spp., Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholera and Vibrio parahaemolyticus. Standard culture-based microbiological techniques and the Kirby–Bauer agar disk diffusion method were employed to isolate and determine antimicrobial susceptibility patterns against 11 selected antibiotics.

Results revealed a high level of bacterial contamination, with 64.71% (44/68) of the samples testing positive for at least one bacterial species. Proteus spp. showed the highest prevalence (44.12%), followed by Staphylococcus aureus (10.29%), Pseudomonas aeruginosa (4.41%), Vibrio cholerae (2.94%), and Vibrio parahaemolyticus (2.94%).

These findings highlight the widespread presence of antimicrobial-resistant food borne pathogens in fish sold in retail markets and emphasize the potential health risks associated with poor handling and hygiene practices.