Medycyna Wet. 64 (4), 457-460, 2008
Berthold A., Rutkowska K.
Growth and production of diarrheal enterotoxin in milk by Bacillus cereus
The aim of this study was to examine the ability of B. cereus, isolated from raw milk and the environment of milk production, to grow and produce the HBL enterotoxin in milk. In this study three B. cereus strains, isolated from raw milk and the surface of teats, were assessed with respect to their ability to grow and produce HBL enterotoxin in milk that has been stored at the following temperature and time combinations: 33–37°C/16-18 h; 4°, 6° or 8°C/7 days. The incubation of the specimen was conducted under aerobic conditions or in stationary culture. The general number of B. cereus was measured before and after the incubation. To detect the HBL enterotoxin, the BCET-RPLA test (Argenta Sp. z o. o.) was used after incubation. All of the strains produced enterotoxin in milk stored at 33-37°C, regardless of the aerobic conditions. The final number of B. cereus strain cells increased by approx. 6-7 logarithmic rows compared with the initial one. All of the strains produced HBL toxin at 8°C, under an oxygen atmosphere. Only one strain produced it under oxygen-limited conditions. Depending on the strain, the final numbers of B. cereus cells increased by 2-6 logarithmic rows compared with the initial ones. None of the examined strains produced the HBL enterotoxin at 6°C and 4°C, regardless of aerobic conditions. The highest permissible temperature for pasteurized milk storage in trade is 8°C in Poland. However, this temperature is not low enough to guarantee product safety, as it allows for diarrheal enterotoxin production and growth, as well as growth of psychrotrophic B. cereus strains. /td>
Keywords: Bacillus cereus, psychrotrophic, milk, diarrheal enterotoxin<