Occurrence of staphylococcus aureus enterotoxin producing strains in raw milk and in meat

Abstract

Milk and milk products, meat and meat products are foods commonly incriminated in staphylococcal food poisoning outbreaks. A study was conducted to investigate the presence of enterotoxigenic staphylococcus aureus (S. aureus) in raw milk and raw meats. Three hundred raw milk samples, 120 beef carcasses, 55 minced beef and 45 dressed chickens were investigated. Isolations were made on mannitol salt agar medium and organisms assayed for enterotoxin A, B, C and D using reverse passive latex agglutination technique. The isolation rate of S. aureus was found to be 61 % from raw milk, 7.5% from beef carcasses, 32.7% from minced beef and 57.8% from dressed chickens. A high percentage ot strains from raw milk ( 74.2%), chickens (69.4%), and minced beef (60%) were found to produce enterotoxins. While only a few from beef carcasses ( 33.3%) produced enterotoxins. Staphylococcal enterotoxin C (SEC) was the most commonly encountered type, with staphylococcal enterotoxin A (SEA) ranking second, staphylococcal enterotoxin B (SEB) third. Staphylococcal enterotoxin D (SED) was least encountered in all the four types of animal products investigated. The data show that raw milk, dressed chickens and minced beef are potential sources of food poisoning enterotoxigenic staphylococci in Kenya, and that increased handling of the meat products increases contamination.