Abstract
Fifty strains of Staphylococcus aureus isolated from clinical specimens were examined for the induction of L-forms by the penicillin-disc technique. They were cultivated on L-form medium which was composed of brain-heart infusion broth, 5% NaCl, 1% special agar, and 15% horse serum. L-forms were successfully induced from a strain, Tasaki, which had been isolated from a patient with ear infection.
The staphylococcal L-forms thus induced were designated as STA-EMT-1 strain. L-colonies were detected initially in five to seven days. After several transfers on L-form media they appeared in a few days, exhibiting a typical, so-called “fried-egg” configuration on L-form medium. Microscopically, the L-colony consisted of dark central granular elements and light peripheral spherical cells, ranging from several to more than ten microns in diameter.
Staphylococcal L-forms could not grow on blood agar plate or any other medium routinely used for bacteria, but could easily be transferred to a fresh L-form medium by means of the agar block technique. They appear to be of stable type. No reversion to the parent bacterial form has occurred to them until the present time after about thirty transfers on L-form media without addition of penicillin.
