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

Milk powders (37 samples) from five different processing centres (A, B, C, D and E) were examined for total viable counts, total staphylococcal counts and staphylococcal enterotoxins. All powders from centres A, B and C contained low numbers of total viable bacteria and staphylococci but five from centres D and E had high total and staphylococcal counts. Nine different staphylococcal species were encountered in low count powders with a wide range of species occurring at each of the five centres. Three species (Staphylococcus capitis, Staph, saprophyticus and Staph. cohnii) were found whose natural hosts are humans. High count powders all contained added fat of various types and had a much more restricted staphylococcal microflora in which Staph. saprophyticus and Staph. cohnii predominated. None of 384 staphylococcal strains isolated were found to be Staph. aureus. In addition, no enterotoxins were detected.