Biotyping and serotyping of Propionibacterium acnes strains isolated from different diagnostic materials.

Fifty strains of Propionibacterium acnes, five strains with the previous designation Corynebacterium parvum and three strains of Propionibacterium avidum were agglutinated by Bacto-Corynebacterium acnes 554 antiserum (Difco); it was not possible to isolate any strain reacting only with 605 antiserum. Only one strain of C. parvum reacted with both sera. 48 (88 per cent) out of 54 strains (P. acnes and C. parvum) belonged to Voss' group I and 25 (47 per cent) belonged to Pulverer's biotype A. Strains from different diagnostic materials differed only biochemically (species acnes and avidum). The relations between these two species are discussed.