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The action of staphylococcal /8 toxin on the erythrocytes of a number of species of animal was described by Bryce and Rountree (1936). These workers found that when the j8 toxin was mixed with the erythrocytes of certain species and the mixture held at 37° C. for one hour there was no lysis, but if it was then transferred to the cold the cells lysed. Christie, Atkins and Munch-Petersen (1944) showed that this lysis could be completed in ruminant erythrocytes at 37° C. by the action of a factor produced during the growth of Streptococcus agalactiae. Wilson and Slavin (1950) and Murphy, Stuart and Reed (1952) showed that certain other organisms, notably some strains of Streptococcus uberis, gave the same reaction, whilst not all strains of Strep, agalactiae did so. Murphy et al. designated the factor responsible for this reaction CAMP. This factor has no demonstrable effect on cells not treated with /3 toxin.During the development in this laboratory of a "spot" plate test to detect Strep, agalactiae in contaminated cultures, and a tube test for the assay of CAMP, several interesting reactions were observed. These reactions form the basis of the work described in this paper. MATERIALS AND METHODS. staphylococcal p toxin.This was prepared from a growth of the pure /3 toxin producing staphylococcus S32A of Bryce and Rountree, kindly supplied by E. Munch-Petersen. A sloppy agar culture of S32A, incubated for 48 hours at 37° C. in an atmosphere of 20 p.c. CO2 was filtered through muslin, centrifuged at about 3,500 r.p.m. for 20 minutes, and filtered through a Seitz E.K. pad. The filtrate, referred to as p toxin, was stored in bottles at 4° C. Standardisation of p toxin.Serial double dilutions of p toxin were prepared in 0-5 ml. quantities in normal (physiological) saline. To each tube was added 0-5 ml. of a suspension of 3 p.c. washed sheep orythrocytes in a 1 in 4 dilution in saline of neutral CAMP factor. Lysis in this system was found to run parallel with titration of p toxin by the usual "hot-cold" method. The last tube showing complete lysis was taken as the end point. CAMP factor.This was produced by growing Strep, agalactiae in crystal violet broth. For stock CAMP factor our strain 519/13/1 was used, the culture being filtered through a Seitz E.K. pad and the filtrate stored in the cold.

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Five methods for the detection of Strep. Agalactiae in milk samples were examined with special reference to their use as direct and indirect tests. Comparison was made of the sensitivity of all tests in detecting excretor cows. In the consideration of methods as direct tests particular attention was paid to their value for screening out frankly negative samples with the minimum amount of work. A newly developed test based on the CAMP reaction, the "spot" test, was found to combine high sensitivity and cheapness, and this is recommended for use under South Australian conditions.

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