On 30 May 2012, Surrey and Sussex Health Protection Unit was called by five nurseries reporting children and staff with sudden onset vomiting approximately an hour after finishing their lunch that day. Over the following 24 h 50 further nurseries supplied by the same company reported cases of vomiting (182 children, 18 staff affected). Epidemiological investigations were undertaken in order to identify the cause of the outbreak and prevent further cases. Investigations demonstrated a nursery-level attack rate of 55 out of 87 nurseries (63·2%, 95% confidence interval 52·2–73·3). Microbiological tests confirmed the presence of Bacillus cereus in food and environmental samples from the catering company and one nursery. This was considered microbiologically and epidemiologically consistent with toxin from this bacterium causing the outbreak. Laboratory investigations showed that the conditions used by the caterer for soaking of pearl haricot beans (known as navy bean in the USA) used in one of the foods supplied to the nurseries prior to cooking, was likely to have provided sufficient growth and toxin production of B. cereus to cause illness. This large outbreak demonstrates the need for careful temperature control in food preparation.

Bacterial endospores are resistant to many environmental factors from temperature extremes to ultraviolet irradiation and are generally more difficult to inactivate or kill than vegetative bacterial cells. It is often considered necessary to treat spores or samples containing spores with chemical fixative solutions for prolonged periods of time (e.g., 1–21 days) to achieve fixation/inactivation to enable electron microscopy (EM) examination outside of containment laboratories. Prolonged exposure to chemical fixatives, however, can alter the ultrastructure of spores for EM analyses. This study was undertaken to determine the minimum amount of time required to inactivate/sterilize and fix spore preparations from several bacterial species using a universal fixative solution for EM that maintains the ultrastructural integrity of the spores. We show that a solution of 4% paraformaldehyde with 1% glutaraldehyde inactivated spore preparations of Bacillus anthracis, Bacillus cereus, Bacillus megaterium, Bacillus thuringiensis, and Clostridium perfringens in 30 min, and Bacillus subtilis in 240 min. These results suggest that this fixative solution can be used to inactivate and fix spores from several major groups of bacterial spore formers after 240 min, enabling the fixed preparations to be removed from biocontainment and safely analyzed by EM outside of biocontainment.

Bacillus cereus can produce α-amylase, which has important industrial production value and can endure high temperatures. The enzymatic characteristics of two α-amylases from B. cereus (B905 and B904) were studied. The results showed that both preserved their activity at 90–100°C. Their thermal stability and enzymatic activity did not depend on Ca2+. However, their protein molecular weights were obviously different. The structural genes of amy905 and amy904 were cloned successfully using the polymerase chain reaction (PCR) and expressed in Escherichia coli. The amy904 and amy905 genes were 1362 bp and 1761 bp long and their protein molecular weights were about 55 kDa and 68 kDa, respectively.

The contamination of pasteurized milk by Bacillus cereus during the filling process was studied in two dairy plants. Samples of pasteurized milk were taken at four different sites along the production line. The samples were stored at 7 °C for 7 d, or at 10 °C for 5 d, before plate counting and random selection of B. cereus isolates. Isolates of B. cereus were typed by the polymerase chain reaction (PCR)-based method randomly amplified polymorphic DNA (RAPD). Samples taken at three different sites between the pasteurizer and the filling machine were all holding similar low concentrations of B. cereus, while an increase of the B. cereus count was seen in the consumer packages. More B. cereus of different RAPD types was growing in the consumer packages than in samples taken just before the filling machine. Several RAPD types found in the consumer packages were not detected in the samples taken just before the filling machine.