Limited genetic diversity of Propionibacterium acnes bacteriophages from human skin

The human skin commensal Propionibacterium acnes is associated with inflammatory acne vulgaris has been implicated in a wide range of opportunistic infections. Bacteriophages that infect P. acnes can be readily isolated from human skin and we have previously sequenced the genome of one such phage with a view to utilising phages for genetic manipulation of P. acnes and phage therapy of acne. The genomes of 14 P. acnes phages were analysed by restriction endonuclease digestion. Several DNA fragments appeared to be shared between the phages. To analyse the phages in further detail, four phages were selected for genome sequencing. All four phages showed similar plaque morphology on lawns of P. acnes and only one demonstrated evidence of lysogeny. All phages were able to infect and lyse all of 32 strains of P. acnes tested. The phages possessed similar sized genomes (29kb) with strikingly similar gene organisation. Structural genes were organised on the left arm and DNA replication genes on the right arm similar to the previously sequenced phage PA6. As with PA6, these phages did not infect other species of propionibacteria. The lack of diversity within phages of P. acnes suggests limited diversity between strains of P. acnes. This may indicate that phage therapy for P. acnes-associated diseases is a possibility with low potential for the development of bacterial resistance.