Isolation and characterisation of Bacillus cereus from pasteurised milk in household refrigerators in The Netherlands

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Published on: December 5, 2016

M C Te Giffel1, R R Beumer, P E Granum

  • 1Laboratòry of Food Microbiology, Agricultural University, Wageningen, The Netherlands.

International Journal of Food Microbiology
|March 3, 1997
PubMed

Insights

Bacillus cereus was found in 40% of Dutch milk samples, with most strains capable of producing enterotoxins. These adaptable B. cereus strains, even those unable to ferment lactose, pose a potential health hazard in milk products.

Area of Science:

  • Food Microbiology
  • Bacterial Pathogenesis
  • Food Safety

Background:

  • Bacillus cereus is a common bacterium found in various environments, including dairy products.
  • Understanding its prevalence and characteristics in pasteurised milk is crucial for public health.
  • Previous studies have indicated the potential for B. cereus to cause foodborne illnesses.

Purpose of the Study:

  • To investigate the incidence and characteristics of Bacillus cereus in pasteurised, low-fat milk stored in household refrigerators in the Netherlands.
  • To assess the carbohydrate metabolism, growth profiles, haemolysin, and enterotoxin production of isolated B. cereus strains.
  • To evaluate the potential health risks associated with B. cereus in milk.

Main Methods:

  • Analysis of 334 pasteurised, low-fat milk samples from Dutch household refrigerators.
  • Isolation and enumeration of Bacillus cereus using standard microbiological techniques.
  • Confirmation of B. cereus isolates using ISO methods and API 50 CHB carbohydrate profiling.
  • Assessment of growth at 7°C, haemolysin production (including haemolysin BL), and enterotoxin production (using Western immunoblot, PCR, and Vero cell assays).

Main Results:

  • Bacillus cereus was isolated from 40% of the milk samples, with generally low counts.
  • B. cereus levels increased with higher storage temperatures and longer storage times.
  • A significant proportion of isolates (20%) fermented lactose, and 53% grew at 7°C, indicating adaptation to milk environments.
  • All tested strains produced haemolysin, with 27% showing the haemolysin BL pattern.
  • 73-76% of tested strains were enterotoxigenic, with lactose-fermenting strains producing more enterotoxin.

Conclusions:

  • Bacillus cereus is prevalent in pasteurised milk and can adapt to refrigerated storage conditions.
  • The high prevalence of enterotoxin production among isolated strains suggests a potential health hazard.
  • Further monitoring and control measures are necessary to mitigate the risk of B. cereus in milk products.

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