Prevalence of Bacillus cereus in the faeces of healthy adults

In a survey designed to determine the prevalence of Bacillus cereus in the faeces of healthy persons, the organism was found in low numbers in 100 (14%) of single faecal specimens from 711 adults in the general population. In addition, in an attempt at assessing the changes in the B. cereus distribution within the faecal flora of the individual, weekly faecal specimens were submitted over a seven-week period by 18 members of staff of two laboratories. The total isolation rate was again 14%, with 15 serotypes represented. In four individuals B. cereus was isolated in two consecutive weeks and in all cases the isolates were of different serotypes. Excretion was never recorded for more than two consecutive weeks. These findings probably reflect the intake of B. cereus in the individual's diet.