OCCURRENCE AND MOLECULAR DETECTION OF LISTERIA SPECIES IN RAW COW MILK FROM SELECTED DAIRY FARMS IN SOKOTO METROPOLIS AND ITS ENVIRONS, NIGERIA

Abstract

Listeria species are important foodborne pathogens that contaminate raw milk and present a significant public health concern globally. This study investigated the occurrence and antimicrobial susceptibility profiles of Listeria species in raw cow milk across intensive, semi-intensive, and extensive dairy management systems in the Sokoto Metropolis and its environs, Nigeria. A total of 150 raw milk samples were collected and analyzed using standard bacteriological isolation methods on selective media, biochemical characterization, and molecular confirmation was performed using Polymerase Chain Reaction (PCR) targeting the genus-specific prs gene. Phenotypic antimicrobial susceptibility profiling was conducted using the Kirby–Bauer disk diffusion method. Out of the 150 raw milk samples examined, 81 (54.0%) yielded presumptive colonies on selective agar, and 12 (8.0%) were confirmed biochemically. However, molecular confirmation verified a molecular prevalence of 0.67%, identifying only one isolate positive for the genus- specific prs gene. No statistically significant association was observed between the occurrence of Listeria species and farm management system (p > 0.05). The recovered prs-confirmed isolate demonstrated phenotypic resistance to cefotaxime and amoxicillin–clavulanic acid, intermediate susceptibility to ampicillin, and complete susceptibility to gentamicin, chloramphenicol, nitrofurantoin, trimethoprim–sulfamethoxazole, ciprofloxacin, tetracycline, and amikacin. It is concluded that though the molecular prevalence of Listeria species in raw cow milk within the study area is low, the presence of a β-lactam-resistant strain emphasises the critical need for continuous molecular surveillance for effective identification and monitoring of pathogenic strains of Listeria species that may impact milk safety within the study area.