Ruth N. Robbins

An enterotoxin-like protein in Staphylococcus aureus strains from patients with toxic shock syndrome.

An enterotoxin-like protein, tentatively labeled enterotoxin F, was isolated from Staphylococcus aureus strains taken from patients with toxic shock syndrome. Antibodies specific for enterotoxin F were prepared in rabbits. Use of these antibodies showed that 130 (91.5%) of 142 S. aureus strains from patients with toxic shock syndrome produced enterotoxin F. Strains from toxic shock patients in eight other countries were identified as enterotoxin F producers. Only a small number of S. aureus strains from sources other than patients with toxic shock syndrome were found to produce enterotoxin F. Twenty-one of 111 controls had low antibody titers (less than 1:100) to enterotoxin F whereas 86 of 92 toxic shock patients had low acute phase antibody titers (less than 1:100) to enterotoxin F. Eight of 52 patients had serum conversion as shown by an increase in antibody titer to enterotoxin F in sera taken 21 to 60 days after onset of the illness. It may be possible to identify persons susceptible to toxic shock syndrome by measuring their antibody titer to enterotoxin F.

Production of Rabbit Antisera to the Staphylococcal Enterotoxins

An immunization method for production of antiserum to the staphylococcal enterotoxins in rabbits is presented. The bleeding schedule is tailored to the enterotoxin type. About 0.5 mg of staphylococcal enterotoxin is used per rabbit and serum harvest begins 11 weeks after the initial injection. Proposed are subcutaneous injections of 1, 3, 10, 20 and 30 μg of toxin with Freunds adjuvant on days 0, 3, 8, 24 and 28, respectively; and five weeks later, injections of 50, 100 and 300 μg on days 0, 3 and 8, respectively. Serum harvest ranges from a 4-week period for enterotoxin A to 8 or more weeks for enterotoxin E. Immunizations with all toxin types using the proposed or similar injection programs produced antibody titers from about 20 to over 100. Individual variation in response of rabbits in the same group was generally 3- to 5-fold, and in extreme instances, 10-fold. Immunization experiments were augmented by booster experiments in which the rabbit variable was held relatively constant by sequentially testing different schedules and doses on the same group of animals.

CHARACTERIZATION OF TYPES OF STAPHYLOCOCCAL ENTEROTOXI NS1,2

The staphylococcal enterotoxins are single polypeptide chains that contain two half-cystine residues that are cross-linked in the native toxin to form a “cystine” loop. Several amino acid residues involving part of this loop appear to be the same for the different enterotoxins which may represent the toxic site. The other part of the cystine loop may be involved in the antigenicity of the toxin which is the basis for identifying them as enterotoxns A-E. The antigenicty of the enterotoxins varies from the similarity of enterotoxins C1 and C2 which have the same major antigenic site to enterotoxins A and B which are apparently unrelated antigenically.