Enterotoxigenicity of Staphylococcus aureus cultures isolated from acute cases of bovine mastitis.

To determine whether staphylococci causing bovine mastitis are potential causes of human intoxications, 142 cultures identified as etiological agents of acute cases and 18 cultures causing chronic cases of staphylococcal mastitis were obtained from investigators in the United States and Canada, examined microscopically, and tested for carbohydrate utilization, terminal pH, catalase, coagulase, egg yolk hydrolysis, gelatin hydrolysis, cytochrome oxidase, urease production, nitrate reduction, micrococcal nuclease, phage type, and enterotoxin production. Three cultures were not confirmed as Staphylococcus aureus. Of the 157 S. aureus cultures, 23 produced staphylococcal enterotoxins. Although a direct relationship between staphylococcal mastitis and outbreaks of staphylococcal food poisoning was not proved, results indicated that staphylococcal infections of the bovine mammary gland represent a significant reservoir of enterotoxigenic strains of S. aureus.