Occurrence of emetic toxin producing Bacillus cereus in the dairy production chain

A collection of 5668 Bacillus cereus isolates, resulting from investigations on sources of contamination to milk in 10 different dairies and 10 farms, was screened for the presence of emetic toxin producing strains, based on phenotypic traits, a specific RAPD-PCR pattern, a sperm motility inhibition test, and was confirmed chemically. No emetic strains (<0.2%) were found in milk at a farm during the grazing period and none was found in environmental samples. Emetic strains were generally rare in milk (<1.0–3.8%) during the stall period but extensive clonal development occurred on one farm in cubicles with deep sawdust bedding. Among 3401 isolates obtained from samples taken along the dairy processing line and in monthly samplings of silo tanks, only 0.05% were emetic toxin producers. However, evidence for an emetic house flora was found in one silo tank. It may be important for the dairy industry to increase surveillance for emetic strains in milk powder and to further optimize the cleaning routines of silos.