Listeria monocytogenes and other Listeria species in retail meat and milk products in Addis Ababa, Ethiopia

Abstract

Background: Listeriosis is one of the important emerging bacterial zoonotic infections worldwide. Among the different species of the genus Listeria, Listeria monocytogenes is known to cause listeriosis in humans and animals. Information on the occurrence and distribution of L. monocytogenes and other Listeria species is very limited both in the veterinary and public health sectors in Ethiopia. Objectives: The present study was undertaken to determine the occurrence and distribution of L. monocytogenes and other Listeria species in retail meat and milk products in Addis Ababa, Ethiopia. Methods: A total of 316 food samples were collected using a cross-sectional study design from September 2003 to April 2004. The techniques recommended by the International Standards Organization (ISO 11290-1, 1996) and the French Association for Standardization (AFNOR, 1993) were employed for the isolation and identification of Listeria species. Serotyping of L. monocytogenes was carried out at the French Authority for Food Safety (AFSSA), Ploufragan, France. Results: Out of the total of 316 samples examined, 103 (32.6%) were found to be positive for Listeria. Listeria species were isolated in 69.8% (37/53), 47.5% (29/61), 43.5% (20/46), 18.6% (8/43), 15.4% (8.52) and 1.6% (1/61) of the pork, minced beef, ice cream, fish, chicken meat and cottage cheese samples, respectively. L. monocytogenes was detected in 5.1% of the samples analysed. It was isolated mainly from ice cream (19.6%) and pork samples (7.5%) followed by minced beef (1.6%), fish (2.3%) and chicken meat samples (1.9%). The serotypes of L. monocytogenes identified belonged to 1/2b, 4b and 4e. In addition to L. monocytogenes, the other Listeria species identified were L. innocua (65.0%), L. seeligeri (8.7%), L. welshimeri (6.8%), L. murrayi (1.9%), L. ivanovii (0.9%) and L. grayi (0.9%). Conclusion: This study demonstrated the widespread occurrence and distribution of L. monocytogenes and other Listeria species in retail meat and milk products in Addis Ababa, Ethiopia.