Bacillus cereus is a Gram-positive, facultatively aerobic spore former whose cells are large rods and with spores that do not swell the sporangium. B. cereus spores are more resistant to heat and chemical treatments than vegetative pathogens such as Salmonella, and E. coli.
Bacillus cereus is responsible for 5% of foodborne illnesses worldwide, causing severe nausea, vomiting and diarrhea. Detecting potential B. cereus as quickly and easily as possible is of paramount importance. B. cereus food poisoning has two recognized types of illness are caused by two distinct metabolites. The diarrheal type of illness is caused by a large molecular weight protein, while the vomiting (emetic) type of illness is believed to be caused by a low molecular weight, heat-stable peptide.
The symptoms of B. cereus diarrheal type food poisoning include watery diarrhea, abdominal cramps, and pain occurs 6-15 hours after consumption of contaminated food. Nausea may accompany diarrhea, but vomiting rarely occurs. Symptoms persist for 24 hours in most instances. The emetic type of food poisoning is characterized by nausea and vomiting within 0.5 to 6 h after consumption of contaminated foods. Occasionally, abdominal cramps and/or diarrhea may also occur. Duration of symptoms is generally less than 24 h.
A wide variety of foods including meats, milk, vegetables, and fish have been associated with the diarrheal type food poisoning. The vomiting-type outbreaks have generally been associated with rice products; however, other starchy foods such as potato, pasta and cheese products have also been implicated. Food mixtures such as sauces, puddings, soups, casseroles, pastries, and salads have frequently been incriminated in food poisoning outbreaks.
Two different methods are described in BAM1 for the detection of B. cereus: (i) plate count method with Mannitol–Egg Yolk–Polymyxin (MYP) agar and (ii) a Most Probable-Number (MPN) method with Tryptic Soy Broth (TSB) supplemented with 0.1% Polymyxin Sulfate. The MPN method allowed for better recovery and therefore for higher counts than MYP2, probably due to the better ability of the broth to recover injured organisms.
A new vial (BCP) was developed specifically for B. cereus detection in the BioLumix system. It uses the CO2 sensor at the bottom of the vial. The medium contains growth promoting ingredients peptones, casein digest and Yeast Extract. Sodium Pyruvate is added to facilitate the resuscitation of damaged Bacillus cells. Manganese Chloride is added to aid the germination of spores. Inhibitors include Cyclohexamide to prevent growth of YM; LiCl, Cyclohexamide and Polymixin B are used as inhibitors.
ATCC 10876- Dark Blue; ATCC 11778- Green; ATCC 14549- Light blue; and ATCC13061-Red
Twenty five cultures of gram negative organisms and Twenty one cultures of gram positive organisms were tested in the BC vial. None of the gram negative organisms grew in the vial and all gram positive organisms did not grow except one strain of Enterococcus feacalis (ATCC 19433). The new BC vial recovers well vegetative cells as well as spores. The method used is very simple, just pipette the diluted sample into the vial. The results are obtained in 24 hours or less. This vial is ready for free product trials.
- E. Jeffery Rhodehamel and Stanley M. Harmon (2001). Bacteriological Analytical Manual, Chapter 14: Bacillus cereus (2001). US Food and Drug Administration.
- N. M. Harper, K.. K. Getty, K. A. Schmidt, A. L. Nutsch, and R. H. Linton. Comparing the Mannitol–Egg Yolk–Polymyxin Agar Plating Method with the Three-Tube Most-Probable-Number Method for Enumeration of Bacillus cereus Spores in Raw and High-Temperature, Short-Time Pasteurized Milk. J. Food Prot.71:473–478.