Isolation and identification of staphylococci from milk powders produced in Northern Ireland

Enterotoxin production by staphylococci isolated from foods in France

Two hundred and thirteen Staphylococcus aureus and 51 other staphylococcal strains were isolated from 121 foodstuffs of current consumption and two cutaneous samples. Their ability to produce staphylococcal enterotoxins was tested and S. aureus strains were biotyped. The S. aureus strains (30.5%) produced at least one of the five known staphylococcal enterotoxins whereas coagulase negative staphylococci did not produce any of them. The raw milk cheeses analysed were primarily contaminated by strains belonging to animal or unspecified biovars. Only 15.9% of the S. aureus strains isolated from these products produced enterotoxins whereas 43% were found to be enterotoxigenic amongst the S. aureus strains isolated from the other foodstuffs. The scheme of biotyping used seems to be reliable, allowing the classification of 73.7% of the strains. S. aureus strains of human biovar origin were most often enterotoxigenic and enterotoxin C was the predominant type identified. It was produced by 66% of the enterotoxigenic strains, singly or in combination with other enterotoxins. Approximately 77% of the human strains also produced enterotoxin C, which is an amazing epidemiological distinctive feature of the strains studied. Moreover ELISA tests used in this work exhibit problems of specificity.