INTERGENERIC AND INTRAGENERIC INHIBITION BETWEEN STRAINS OF PROPIONIBACTERIUM-ACNES AND MICROCOCCACEAE, PARTICULARLY STAPHYLOCOCCUS-EPIDERMIDIS, ISOLATED FROM NORMAL SKIN AND ACNE LESIONS

Two hundred and forty-one strains of resident skin bacteria comprising 93 isolates of Propionibacterium acnes and 148 of Micrococcaceae derived from 36 acne patients and 8 control subjects were screened for their ability to inhibit 32 indicator strains, including 20 strains of P. acnes and 12 strains of Staphylococcus epidermidis derived from patients with all grades of acne and from normal skin. Fifty-three strains (22%) showed some activity against at least one indicator strain. Both broad- and narrow-spectrum inhibition was detected. Inhibitory isolates of P. acnes outnumbered inhibitory Micrococcaceae by four to one. There was a low frequency of inhibition of S. epidermidis by Micrococcaceae (2.7%) and by P. acnes (1.1%) and a higher frequency of inhibition of P. acnes by Micrococcaceae (9.5%) and by P. acnes (40.8%). Furthermore, 81.8% of the subjects sampled possessed strains inhibitory to P. acnes. The significance of this finding is, as yet, unknown. No difference in the prevalence of active strains in normal (20%) and acne (22.5%) skin was detected. These findings suggest that the possession of inhibitory strains and conversely the possession of sensitive strains does not predispose to acne.