A Staphylococcus aureus variant was produced from a typical pathogenic strain
by passage in semi-synthetic broth. It possesses surface antigen serologically
identical to Smith surface antigen, but the variant differs from typical Smith strains
in that it is bound coagulase positive, forms compact colonies in soft serum agar and
is avirulent for mice.
The surface antigen is immunogenic, but immunity experiments stressed the
importance of the protective properties of somatic antigens.