Isolation and identification of Listeria species along the milk value chain in one region of Tanzania

Abstract

Milk is an important source of nutrients in the diet. However, due to its nutritional nature it also serves as an ideal medium for growth and development of various microorganisms under suitable conditions. It is a staple food, which is linked to zoonotic pathogens. This study was carried out in two districts (one region namely Tanga) of Tanzania to evaluate the awareness of farmers on milk contamination and to estimate microbial load along the milk value chain. In total 114 respondents were visited to conducted interviews on awareness as well as strategies for solving the problem of milk contamination. Subsequently milk samples were aseptically collected from each of the 114 respondents for laboratory analyses using the standard ISO procedures for food microbial analyses in particular the horizontal methods. We have showed that there are poor hygienic practices by the majority of actors along the milk value chain in Tanga region. Concerning microbial level, our results revealed that above 90 percent of all samples collected showed total plate count (TPC) above standard acceptable in the Eastern Africa countries (EAC) of 2.0x105 CFU/ml. It was also shown that there was more contamination in milk samples obtained from the household farms compared to those which were collected from the milk suppliers and in the extensive farming system than in the intensive system (P < 0.05). Moreover, three Listeria species namely L. innocua, L. ivanovii and L. monocytogenes were identified. L. monocytogenes were isolated and identified as the common contaminants in milk along the value chain in the study region.