Investigation of Bacillus cereus contamination sites in a dairy plant withRAPD-PCR

The usefulness of RAPD-PCR as a typing method for investigation of Bacillus cereus isolates from a dairy plant was evaluated. A 1-d in-depth sampling study along the entire production line was performed and long-term sampling of products was conducted over two pears. In addition, farm bulk tank isol ates were collected. Isolates from an individual sample during storage at 7 degrees C were often identical. Large clusters of identical isolates were found in the silo tank in the 1-d study and in samples from the long-term s tudy. In combination with analytical data, these results indicated a prolon ged contamination problem caused by a mesophilic strain early in the produc tion chain. Detailed and useful information on occurrence of psychrotrophic B. cereus was obtained along the production line and among products. RAPD- PCR appeared to be a useful typing method for B. cereus isolates. In combin ation with carefully planned sampling and microbiological analysis, RAPD co uld be helpful in solving dairy contamination problems in pasteurized milk. (C) 2000 Elsevier Science Ltd. All rights reserved.