Studies on a CO2-dependent staphylococcus.

A dwarf strain of Staphylococcus aureus was isolated in pure culture from styes on the eyelid of a young woman. Incubation of pus cultured on horse blood agar in 5% CO2 yielded a typical golden staphylococcus, coagulase and catalase positive and penicillin sensitive, but on duplicate plates in air the growth was of tiny white colonies only 0.25 mm. in diameter. These were penicillinsensitive Gram-positive cocci, but the catalase and coagulase tests were negative. Subcultured with added C02, typical 2 mm. colonies of Staphylococcus aureus developed, but in air all grew as dwarfs. This coccus was of bacteriophage type 52A. The patient, who had used penicillin ointment, was now given systemic penicillin and her styes healed, but the dwarf staphylococcus was present in nasal swabs a month later. Swabs from her mother, who had a palmar abscess and then a sore throat, also yielded a dwarf staphylococcus of type 52A which required added CO2 for normal growth.