Abstract
Listeria monocytogenes is of major significance in human and veterinary medicine. Most human Listeria infections are foodborne and the association of contaminated milk and dairy produce consumption with human listeriosis is noteworthy. In Ethiopia, there is limited data regarding the prevalence of L. monocytogenes in raw bovine milk and dairy products. The aim of this study was, therefore, to determine the prevalence of L. monocytogenes in raw bovine milk and dairy produce. A total of 443 milk and milk product samples were microbiologically analyzed following methods recommended by the U.S. Food and Drug Administration Bacteriological Analytical Manual to isolate Listeria spp. The overall prevalence of Listeria spp. was 28.4% and specifically that of L. monocytogenes was 5.6%. Taking the prevalence of Listeria spp. into consideration, cheese was found to be highly contaminated at 60%, followed by pasteurized milk samples (40%), raw milk (18.9%) and yoghurt (5%). Considering the prevalence of Listeria monocytogenes only, raw milk had the lowest contamination while cheese had the highest, followed by pasteurized milk and yoghurt. Raw milk and milk products produced in urban and peri-urban areas of central Ethiopia were contaminated with pathogenic bacteria, L. monocytogenes. The detection of this pathogen in raw milk and milk products warrants an urgent regulatory mechanism to be put in place and also the potential role of milk processing plants in the contamination of dairy products should be investigated.
Highlights
Listeria monocytogenes is of major significance in human and veterinary medicine
1Urban area =Addis Ababa and Debre-Zeit; 2Peri-urban area =Asela and Selale; 3Not differentiated at species level by biochemical tests sample types followed by pasteurized milk samples, yoghurt samples and the lowest contamination was noticedin raw milk samples (Table 1). This difference in prevalence of both L. monocytogenes and the overall other Listeria spp. was statistically significant (p < 0.05). Both raw bovine milk and milk product specimens in this study were contaminated with Listeria species
The overall prevalence for Listeria spp. (28.4%) reported in this study is slightly higher than prevalence observed by Mengesha et al who isolated Listeria spp (26.6%) from ready to eat food that included: pasteurized milk, cheese, ice cream, and cakes in Addis Ababa, Ethiopia [19]
Summary
Listeria monocytogenes is of major significance in human and veterinary medicine. Most human Listeria infections are foodborne and the association of contaminated milk and dairy produce consumption with human listeriosis is noteworthy. Conclusions: Raw milk and milk products produced in urban and peri-urban areas of central Ethiopia were contaminated with pathogenic bacteria, L. monocytogenes. Starting in the 1960s, as a result of the introduction and widespread use of refrigerators, processed foods and extended shelf life foods became more associated with listeriosis due to L. monocytogenes [5]. This pathogen in addition to its zoonotic potential is an important environmental contaminant of public health significance [6]. The prevalence was found to differ from place to place, based on hygiene, food content and environmental contamination rate of the specific areas [6]
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