Prevalence of Listeria Species in Ready to Take Milk and Meat Products in Nairobi and Its Environs, Kenya

Abstract

Listeriosis is one of the leading causes of death in food-borne infections globally. The disease has mortality rates between 30-50%, especially in high-risk groups. The disease is caused by Listeria monocytogenes, a pathogenic bacterium in the genus Listeria. Currently, in Kenya, there’s limited information on the existence of Listeria spp. in milk and meat products. Therefore, the present study aimed to ascertain the incidence of Listeria spp. in ready-to-eat meat and milk products in the city of Nairobi and its surroundings. We collected 570 meat and milk products from selected retail markets. Isolation of Listeria spp. was carried out per the bacteriological analytical manual protocol of the food and drug administration. Identification of suspected colonies was done through colonial morphology and biochemical tests. Confirmation of the genus and species of the isolates was done through multiplex PCR. Out of the total samples, 8.59% were confirmed for Listeria spp. Out of these isolates, 21(42.8%) were found in milk products such as milk powder 1/17(5.8%), short life pasteurized milk 1/66(1.5%), long life pasteurized milk 3/62(4.83%) and pasteurized milk from dispensing machines 16/20(80%). The rest, 28/49(57.2%) were obtained from meat products namely, ham 2/37(5.4%), brawn 13/73(17.8%), polony 8/27(29.6%), salami 1/6(16.7%) and ready to eat meat bites 4/77(5.19%). Listeria monocytogenes were detected in 22(3.86%) samples, with the highest prevalence being from milk from dispensing machines (68.18%). Of the other Listeria isolates, 27/49(55%) and 2(7.4%) were identified as Listeria welshimeri, while 3(11.11%) were identified as Listeria innocua. The remaining isolates were unidentified Listeria. The study concluded that Listeria spp. and Listeria monocytogenes in particular is present in milk and meat products sold in retail markets in Nairobi and its environs.