Relation of mucoid growth of Staphylococcus aureus to clumping factor reaction, morphology in serum-soft agar, and virulence.

The growth characteristics of several strains of Staphylococcus aureus in Brain Heart Infusion and in a modified Staphylococcus Medium No. 110 were compared. In the latter medium all of the strains studied showed an increased mucoid character. Some of the strains studied showed a greater potential to synthesize excess slime layer material than others. The highly mucoid strains grew as diffuse-type colonies in modified Staphylococcus Medium No. 110 serum-soft agar and reacted as though they were negative in the test for clumping factor. These strains were also found to be more virulent when used to challenge normal mice intraperitoneally.