Prevalence of Listeria monocytogenes and Listeria species and associated risk factors for contamination of milk and cottage cheese along the value chains in Ethiopia

Anwar Hassen; Abdi Keba; Mekya Seid Ebrai; Hassen Mamo; Tekalign Kejela Geleta; Tesfaye Sisay Tessema; Jessie Vipham; Jasna Kovac; Ashagrie Zewdu

doi:10.1016/j.ijfoodmicro.2024.111021

Prevalence of Listeria monocytogenes and Listeria species and associated risk factors for contamination of milk and cottage cheese along the value chains in Ethiopia

Int J Food Microbiol. 2024 Dec 13:429:111021. doi: 10.1016/j.ijfoodmicro.2024.111021. Online ahead of print.

Authors

Anwar Hassen¹, Abdi Keba², Mekya Seid Ebrai³, Hassen Mamo⁴, Tekalign Kejela Geleta⁵, Tesfaye Sisay Tessema⁶, Jessie Vipham⁷, Jasna Kovac⁸, Ashagrie Zewdu⁹

Affiliations

¹ Department of Microbial, Cellular and Molecular Biology, College of Natural and Computational Sciences, Addis Ababa University, P.O. Box 1176, Ethiopia; College of Veterinary Medicine, Haramaya University, PO Box 138, Dire Dawa, Ethiopia.
² International Livestock Research Institute, P.O. Box 5689, Addis Ababa, Ethiopia.
³ Department of Biology, College of Natural and Computational Sciences, Mizan-Tepi University, P.O. Box 121, Tepi, Ethiopia.
⁴ Department of Microbial, Cellular and Molecular Biology, College of Natural and Computational Sciences, Addis Ababa University, P.O. Box 1176, Ethiopia.
⁵ Department of Biology, College of Natural and Computational Sciences, Mettu University, P.O. Box 318, Mettu, Ethiopia.
⁶ Institute of Biotechnology, Addis Ababa University, P.O. Box 1176, Ethiopia.
⁷ Department of Animal Science and Industry, Kansas State University, 247 Weber Hall, Manhattan, KS 66506, United States.
⁸ Department of Food Science, The Pennsylvania State University, 437 Erickson Food Science Building, University Park, PA 16802, United States.
⁹ Center for Food Science and Nutrition, Natural and Computational Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. Electronic address: ashagrie.zewdu@aau.edu.et.

PMID: 39689567
DOI: 10.1016/j.ijfoodmicro.2024.111021

Abstract

This study aimed to comprehensively examine the prevalence of L. monocytogenes and Listeria spp. in dairy products including raw milk, pasteurized milk, and cottage cheese, and identify potential risk factors for contamination throughout the dairy value chain in major milk sheds in Ethiopia. We collected 912 samples, comprising 736 milk samples (368 raw and 368 pasteurized) and 176 cottage cheese samples, from the Oromia, SNNP, and Amhara regions. The isolation of L. monocytogenes and Listeria spp. followed the EN ISO 11290-1: 2017 standards, with confirmation via PCR targeting the lmo2234 and iap genes. The overall prevalence rates were 12.2 % for Listeria spp. and 4.7 % for L. monocytogenes. Notably, the prevalence of Listeria spp. (P = 0.024) and L. monocytogenes (P < 0.001) varied significantly across regions. Raw milk showed the highest prevalence of Listeria spp. at 15.2 %, followed by pasteurized milk at 12.2 %, and cottage cheese at 5.7 %, with these differences being statistically significant (P = 0.006). The prevalence of Listeria spp. differed significantly (P = 0.001) among the value chain stages (producers, collectors, processors, and retailers) and was 12.5 %, 17.9 %, 17.4 %, and 7.1 %, respectively. Furthermore, the prevalence rates in cottage cheese from producers and retailers were significantly different at 6.8 % and 4.5 % (P = 0.001). The prevalence of L. monocytogenes among milk producers, collectors, and processors was also significantly different, at 4.4 %, 5.4 %, and 12.0 % respectively (P < 0.001). Filtration of milk and cooling for preservation of milk were significantly associated with Listeria spp. or L. monocytogenes contamination at milk collectors' level (P < 0.05). These findings underscore the need for targeted interventions focused on the risk factors identified here to mitigate Listeria contamination in the dairy sector.

Keywords: Contamination; Dairy products; Ethiopia; Listeria monocytogenes; Risk factor; Value chain.