Prevalence of the Staphylococcal Enterotoxins Genes in Raw and Milk Products along the Value Chain in Mbeya and Mbozi Districts, Tanzania

Abstract

The study determined the prevalence of genes coding for Staphylococcal enterotoxins (SEs) from Staphylococcus aureus isolates in milk produced and sold in Mbeya and Mbozi districts in Tanzania. Samples of raw milk (n=300), boiled hot (ready-to-consume) milk (n=72) and sour milk (n=72) were randomly collected from smallholder dairy farmers, milk collection points (MCP) and milk shops. Laboratory analysis showed that 59.7% of the milk samples contained Staphylococcus species. Biochemical tests showed that 12.4% of the isolates were positive for S. aureus, of which 5.6, 2.5 and 4.3% were from samples collected from farmer’s herd milk, MCP and milk shops, respectively. Furthermore, multiplex Polymerase Chain Reaction (mPCR) results showed that 36.4% of the total S. aureus isolates (n=55) had SEs genes. Frequently observed gene was Sea (32.6%) while Sej was not detected in any of the isolates. The distribution of the SEs genes along the milk market channel showed 35, 15 and 50% of the genes came from isolates samples collected at farm level, MCP and milk shops, respectively. Moreover, no statistical difference were observed for SE coding gene between the districts and seasons, though higher (65%) prevalence of S. aureus isolates carrying SEs genes were observed in dry than wet season (35%). The prevalence of SE coding gene in raw, boiled hot and sour milk were 4.3, 5.6 and 4.2%, respectively. The results obtained show that milk produced and marketed in the two districts contained S. aureus isolates expressing gene for enterotoxins production which pose a potential public health risk. Hence, the results indicate the need to institute proper hygienic measures by all milk stakeholders in order to avoid contamination of milk with S. aureus. Further studies on the diversity and distribution of enterotoxins producing S. aureus in the Southern highlands and other areas in the country are recommended.

Keywords: Boiled hot milk, sour milk, enterotoxins, Staphylococcus aureus, Multiplex PCR