Assessment of microbial quality of raw cow’s milk and antimicrobial susceptibility of selected milk-borne bacteria in Kilosa and Mvomero districts, Tanzania

Abstract

Milk is an important source of nutrients to human and animals, but due to its high water activity and nutritional value it serves as an excellent medium for growth of many kind of microorganisms under suitable conditions. The present cross sectional study was conducted to assess microbial quality of raw cow milk and to determine antimicrobial susceptibility of the selected common milk-borne bacteria in Kilosa and Mvomero districts, Morogoro region. A total of 56 respondents were interviewed and subsequently, milk samples were collected for laboratory analysis including microbial quality assessment and antimicrobial susceptibility tests. Results showed that, majority of small-scale livestock keepers were males with no formal education, managing their cattle in dirty environments, practicing extensive grazing system on communal grazing area and treat sick animals themselves. Common antimicrobial agents used were antibiotics. Several factors were observed to predispose milk to microbial contamination. Furthermore, results indicated that 33.9% of respondents consume milk from animals that are under medication, 94.6% of them did not adhere to withdrawal periods, 76.8% of respondents consume raw milk while 78.6% consume milk products made from raw milk. Generally, 85.7% of milk samples had significantly (P < 0.05) higher total bacterial count than the recommended level of 2.0 x 106 cfu/ml by EAC standards. Isolated bacteria included Listeria spp., Staphylococcus aureus, Escherichia coli, Salmonella spp., Pseudomonous aeruginosa and Proteus spp. All isolates were resistant to ampicillin but susceptible to gentamycin, and 91.2% of isolates showed multi-drug resistant to more than two antibiotic drugs. This study concludes that the quality of raw cow milk was poor; unhygienic practices and poor animal husbandry at farm level predispose farmers, consumers and the public to risk of contracting milk-borne infections and associated bacterial resistances. It is recommended that veterinarians, extension officers and all stakeholders should play their roles in order to ensure safe quality milk delivery to consumers.