Studies on bacteriophages of Propionibacterium acnes.

With the help of adaptation experiments, 61 phage preparations out of 36 Propionibacterium acnes bacteriophages (32 isolated by us and 4 sent from abroad) were established. On the basis of their stability, spectrum of activity, and virulence, 13 phages were selected for phagetyping. 58 well-classified P. acnes strains were grouped into 7 phage-types. 7 strains of P. granulosum, two strains of P. avidum, and one yet ungroupable microserophilic propionibacterium strain were resistant to all 61 phages, even when tested in 100 X RTD. A combination of phagetyping with biotyping resulted in data especially useful for the differentiation of P. acnes.