Molecular serotype and evolutionary lineage of Listeria monocytogenes isolated from different Nigerian food items

Abstract

The molecular serotypes and the evolutionary lineage of Listeria monocytogenes isolated from various foods in Nigeria are yet to be documented. Consequently, popular uncooked food items known locally as Okazi Utazi, Onugbu, Ogbono, Garri and Egusi obtained from plants botanically known as Gnetum africanum, Gongronema latifolium, Vernonia amygdalina, Irvingia gabonensis, Manihot esculanta Crantz and Colocynthis Citrullus, respectively were analyzed. Molecular serotype of three chosen isolates was determined using multiplex polymerase chain reaction (PCR) serotyping before analysis based on prfA virulence gene cluster of L. monocytogenes was carried out to establish the evolutionary lineage. There was no L. monocytogenes detected in foods from I. gabonensis, M. esculanta Crantz and C. citrullus. However, the vegetables from G. africanum, G. latifolium and V. amygdalina showed the presence of the organism and chromogenic tests carried out on the three strains chosen from oxford formulation media indicated that they were not other non-pathogenic strains of Listeria. The V3 region of 16S rRNA gene of one strain showed that a close relative of the isolate is a strain implicated in an outbreak of listeriosis. Leafy vegetables could be a major vehicle for transmission of L. monocytogenes in Nigeria since this pathogenic bacterium occured in different vegetables analyzed.

Key words: Listeria monocytogenes, serotype, lineage, pathogenic potential, Nigerian food.