1. Certain strains of lactose and non-lactose-fermenting coliform bacilli have been found to possess a common agglutinogen. This antigen is found in both motile and non-motile smooth strains and appears to be distinct from ‘H’, ‘O’ and rough antigens, and from the X antigen described by Topley & Ayrton. In certain respects it seems to resemble the Vi antigen of Felix & Pitt, notably in the inhibitory effect it exerts on ‘O’ agglutination. It is, however, not associated with virulence and is of relatively wide distribution.2. The strains, when inoculated into rabbits, stimulate the production to high titre of an agglutinin which can be absorbed out completely by any one of the strains.3. Subculture of the strains under certain conditions results in the loss of the antigen and the development of specific variants.4. Agglutinins to these strains have been found in certain diagnostic sera and may prove a possible source of error, particularly if slide agglutination is relied on for identification.We take this opportunity of expressing our thanks to Prof. G. S. Wilson for the loan of Bact. typhi-murium ‘X’ antiserum.

SummaryEight explosive outbreaks of food poisoning, occurring in school canteens in England during 1953 and affecting 1190 known cases, are described. The clinical features were characteristic of the toxin type of illness. No deaths occurred.The food causing all of these outbreaks was prepared from spray-dried skim milk powder. It was not subsequently heat-treated and was usually consumed 3–4 hr. after preparation.The spray-dried milk powder proved to contain a high content of bacteria, including large numbers of Staph. aureus, of a phage pattern often associated with food poisoning. The assumption was therefore made that these outbreaks were caused by staphylococcal enterotoxin.Because the food was often consumed within 3–4 hr. of reconstitution of the milk powder—before, in fact, the staphylococci had had time to grow—it is concluded that the poisoning must have been due mainly to pre-formed toxin.Consideration is given to the opportunities for the formation of toxin in a spray-drying plant, and reasons are brought forward for believing that it is formed mainly in the balance tank where the warm milk is kept, sometimes for several hours, before passing into the final drying chamber.The processing of the milk and the precautions for preventing contamination of the finished product are discussed.

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