Applied Microbiology

In Tanzania pastoralists such as the Maasai and small urban farmers are responsible for the country’s milk production, whereby 80% of the national milk is sold without regulation. This study set out the identification and typing of Staphylococcus aureus (SA) isolated throughout the milk chain in Tanzania. Samples were taken from production-level (pastoralists, urban farmers), collectionlevel (middlemen and depots), processors (dairies) and retailers (kiosks). Samples were analyzed for coagulase positive staphylococci and subsequently typed by enzymatic activities, enterotoxin production, lyses by phages, Pulse-field-gel electrophoreses and the resistance pattern to antibiotics. All in all 200 milk samples were collected in regions of Dar-es-Salaam and Lake Victoria, respectively. 37 of the 200 samples (18.5%) were identified as SA positive. 11 different biotypes were found and the predominant type accounted for 21.6% of all SA isolates (8/37). 32%, 43% and 92% of the isolates were β-hemolytic (12/37), egg yolk (16/37) and clumping factor positive (34/37). 54.1% (20/37) were positive for enterotoxin genes and 81.1% (30/37) of all strains were Penicillin resistant, further 37.8% of the strains were resistant to ≥2 antibiotics. 43% (16/37) of all strains were non-typeable by a set of 32 phages containing human, bovine and small ruminant phages. 43.2% (16/37) of the isolates were lysed by bovine phages. The most common phage types were type 81 (human, 15 isolates), 108 (bovine, 11 isolates) and type 117 and 111 (bovine, 7 isolates each). We can conclude that milk in Tanzania is an important reservoir and vector of enterotoxigenic, antibiotic resistant strains of Staphylococcus aureus.