Bacillus cereus

Hugh Pennington

Bacillus cereus has infected premature babies in London, Brighton, Peterborough, Cambridge, Luton and, possibly, Southend and Basildon. One has died. Contaminated intravenous nutritional food was the route of transmission.

Bacillus cereus is everywhere. Its natural home is soil, water and vegetation, and it is found in most raw foods, particularly cereals. It produces tough spores, which are heat resistant (they survive boiling), and toxins. It is classified in the textbooks as a cause of food poisoning. The emetic kind happens when cooked rice has been kept warm for a while; the spores germinate, the organism grows, and tough toxins build up in the food, causing vomiting. The diarrhoeal kind happens after the consumption of grossly contaminated food. The toxins are produced in the intestine and cause diarrhoea.

Investigating infections can be difficult because the bacterium is so tough and so common: pseudo-outbreaks have been described where it seemed to be causing blood-stream infections, but turned out instead to be a contaminant in the alcohol used to clean the skin before blood samples were taken. Outbreaks have occurred – rarely – in neonatal units after contamination of parts of the equipment used in the mechanical respiration of very sick babies. It has caused very nasty infections after eye surgery.

Contamination of intravenous fluids is feared. Between 29 February and 2 March 1972 five patients who had received dextrose drips died at Devonport Hospital. The fluid was contaminated with bacteria (not Bacillus cereus). The sterilisation process for a batch of 660 bottles prepared on 6 April 1971 had been faulty: the lower trays of the autoclave were not heated enough. The bottles at the top, where testing was done, were OK.

But for Bacillus cereus to contaminate a product designed for intravenous administration is without precedent. Incidents like Devonport (caused by completely different bacterial species) have meant that manufacturers are obsessional about preventing contamination in their products. In this incident the extreme susceptibility of neonates to infection may have made things much worse.

Cecil Clothier conducted an Inquiry into Devonport. He reported in July 1972. The least we can hope for is that the result of the investigation into the current outbreak is published as quickly.