1. An outbreak of food poisoning due to Salmonella typhi-murium phage-type la is described.
2. Bread and (or) bakery confectionery eaten by all but two of the victims, had originated from a particular bakery firm.
3. S. typhi-murium phage-type 1a was found in the stools of an apprentice baker, a female packer of cakes and bread, and in three female counter-hands. The apprentice baker was responsible for the preparation and decoration of the confectionery which was distributed to the branch-shops and other establishments throughout the area.
4. S. typhi-murium was not found in any of the raw materials used at the bakehouse.
5. The cases which arose at a residential school for cripples gave a ratio of six cases to eight symptomless excretors.
6. Seven weeks after the start of the outbreak the last of the infected food-handlers was considered to be free from infection and fit to return to work.
Twelve weeks later the last member of the public was declared to be negative.
Thanks are expressed to Dr Joan Taylor of the Salmonella Reference Laboratory for her advice and assistance in the preparation of this paper, and to the staffs of the Public Health Laboratory and Public Health Department, Edmonton, N. 9, for their help and co-operation during the investigation.