Phenotypic and Molecular Identification, Prevalence and Distribution of Listeria spp in Lactuca sativa, Daucus carota and Brassica oleracea Obtained from Selected Markets in Lagos State, Nigeria

Abstract

Listeria monocytogenes is a foodborne pathogen of significant public health concern particularly when associated with fresh vegetables that are consumed raw or minimally processed. A total of 354 vegetable samples were collected from five major markets and analysed using standard culture, morphological and biochemical methods, followed by polymerase chain reaction and sequencing for molecular confirmation. Mean bacterial counts varied significantly across markets with vegetables from Sabo Yaba recording the highest microbial loads while Idumota recorded the lowest. Molecular analysis confirmed the presence of Listeria monocytogenes, Listeria innocua, and Listeria ivanovii, with L. monocytogenes being the predominant species. Phylogenetic analysis revealed clear clustering of isolates according to species and demonstrated close genetic relatedness to reference strains. The overall prevalence of Listeria species ranged from 17.80 percent to 19.49 percent across the vegetables studied with cabbage showing the highest contamination rate. The findings highlight the widespread occurrence of Listeria species in fresh vegetables sold in open markets and underscore the need for improved hygiene practices and routine molecular surveillance to reduce the risk of listeriosis.