Screening and Molecular Identification of Listeria monocytogenes in Ready-to-Eat Foods at Fast Food Outlets in Port Harcourt

Listeria monocytogenes is a facultative intracellular bacterial pathogen capable of causing severe listeriosis, particularly in immunocompromised individuals, pregnant women, and neonates. Ready-to-eat (RTE) foods sold in informal food service settings represent a significant listeriosis transmission route. This study screened RTE food products from fast food outlets in Port Harcourt, Rivers State, South-South Nigeria for L. monocytogenes contamination. One hundred food samples including cooked meat, salads, sandwiches, and fried plantain were collected aseptically. Pre-enrichment was conducted in Listeria Enrichment Broth followed by selective plating on PALCAM agar. Suspected colonies were confirmed by PCR targeting the hly (listeriolysin O) and iap genes for species-level identification. L. monocytogenes was confirmed in 17% of tested food samples, with the highest contamination prevalence in diced salad and cooked meat products. Serogroup 4b, associated with the majority of clinical listeriosis outbreaks, was detected in 41% of positive isolates. These findings underscore significant contamination risks in Port Harcourt's informal food sector and highlight the need for mandatory food safety enforcement. Keywords: Listeria monocytogenes, ready-to-eat food, hly gene, PCR, Port Harcourt.