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04.11.2024 - Analytics

Bacillus cereus as a cause of foodborne intoxications (1)

Due to a recent fatality, where the cause is currently suspected to be a Bacillus cereus intoxication, we would like to provide you with important information about this bacterial toxin producer below. 

General Information:

Bacillus cereus is a rod-shaped, gram-positive bacterium that is widely distributed in the environment and often associated with food poisoning (vomiting and/or diarrhea). It is known for the formation of heat-resistant spores. These spores are heat stable and can partially survive heating steps in the manufacturing process. 

Origin: 

These bacteria and their spores are widespread in our environment. They can be found in soil, dust, water, animals, and humans. Therefore, contamination of virtually all raw plant and animal foods with this germ is possible.

Significance:

Spores of these bacteria can germinate after a heating step in food and proliferate under insufficient cooling and suitable environmental conditions. To avoid increased germination, it is important to quickly pass through the critical temperature range between 10°C and 60°C after heating. Particular caution is advised when cooling large portions. Foods at risk include cooked rice, pasta, sauces, dairy products, salads/vegetables, and desserts. 

These bacteria play a special role as causes of group illnesses in community catering. Therefore, they are of great importance in community catering, gastronomy, and private households. 

Primary Reasons for Elevated Germ Counts: 

• Too low temperatures during warming (typically, warming temperatures of >+60°C are required)
• Too long cooling phase. The critical temperature range between 10°C and 60°C must be passed as quickly as possible (generally max. 3 hours)
• Insufficient cooling and/or overripening of food (overestimation of shelf life)
• Microbially contaminated raw materials, e.g., herbs, spices, flours...

Growth Conditions:

• Temperature: Growth at 4 - 50°C, toxin production at 37 - 42°C
• pH Value: Growth at 4.3 – 10.5, toxin production up to max. 10.0
• aw Value: Growth up to min. 0.92 – 0.95
• Salt Tolerance: 0.5 – 9 %
• Oxygen Requirement: Facultative anaerobic, preferably aerobic

At What Temperatures Do These Microorganisms Die?

In general, it can be assumed that vegetative bacteria are killed by heating to +72°C for at least two minutes or by an equivalent process. With foods, it should be noted that the temperature-time combination must be achieved in the core of the product to kill the bacteria safely. 

However, spores of these bacteria are often present in foods. These are generally highly heat-resistant and can even survive cooking processes. 

Examinations for Bacillus cereus:

We offer you quick and reliable examinations for presumptive Bacillus cereus. In addition to ISO procedures, we also regularly apply an accredited rapid method in our laboratory. This takes only 1 day, instead of the examination duration of 2-3 days when applying ISO methods. 

Through further molecular biological methods, we can also distinguish between various species within the Bacillus cereus group.

In general, we offer the following rapid methods in our laboratory: 

Parameter                         Examination Duration                          Examination Principle                            Accreditation

Salmonella                            1 Day                                                           RT-PCR                                                        Yes

TentaSpeed

Listeria monocytogenes/             6 Hours                                                  RT-PCR                                                    No

Listeria spp. 

Listeria monocytogenes/              1 Day                                                        RT-PCR                                                    Yes

Listeria spp.

Cronobacter spp.                          1 Day                                                         RT-PCR                                                  Yes

STEC/ VTEC                                  1 Day                                                         RT-PCR                                                 Yes

Campylobacter spp.                      2 Days                                                      Cultural                                                  Yes

Presumptive Bacillus cereus            1 Day                                                      Cultural                                                  Yes

Yeasts and Molds                      3 Days                                                     Cultural                                                 Yes

Lactic Acid Bacteria                      2 Days                                                     Cultural                                                 Yes

Pseudomonads                            2 Days                                                     Cultural                                                  Yes

Coagulase-positive

Staphylococci                               1 Day                                                       Cultural                                                 Yes

Legionella                                      6 Hours                                               RT-PCR                                                 No

Identification / 

Strain Comparison                            2 to 24 Hours                                       Maldi-Tof                                                Yes

Consult our experts on topics related to Bacillus cereus. We provide competent advice and deliver quick and reliable results. 

For further inquiries, our customer advisors or Dirk Lorenz are available by phone at 0781/96947-23 or by email at dirk.lorenz@bav-institut.de.