Abstract
BackgroundPropionibacterium acnes is a commensal of human skin but is also known to be involved in certain diseases, such as acne vulgaris and infections of orthopaedic implants. Treatment of these conditions is complicated by increased resistance to antibiotics and/or biofilm formation of P. acnes bacteria. P. acnes can be infected by bacteriophages, but until recently little has been known about these viruses. The aim of this study was to identify and characterize inducible phages from P. acnes on a genetic and morphological basis.ResultsMore than 70% (65/92) of P. acnes isolates investigated have inducible phages, classified morphologically as Siphoviruses. The phages have a head of 55 nm in diameter and a tail of 145–155 nm in length and 9–10 nm in width. There was no difference in carriage rate of phages between P. acnes isolates from deep infections and isolates from skin. However, there was a significant lower carriage rate of phages in P. acnes biotype IB, mostly attributed to the low carriage rate of inducible phages in biotype IB isolated from deep tissue. Most phages have a strong lytic activity against all P. acnes isolates with inducible phages, but have less lytic activity against isolates that have no prophages. Phages only infected and lysed P. acnes and not other closely related propionibacteria. All phages could infect and lyse their non-induced parental host, indicating that these prophages do not confer superinfection immunity. The phages have identical protein pattern as observed on SDS-PAGE. Finally, sequencing of two phage genes encoding a putative major head protein and an amidase and showed that the phages could be divided into different groups on a genetic basis.ConclusionOur findings indicate that temperate phages are common in P. acnes, and that they are a genetically and functionally homogeneous group of Siphoviruses. The phages are specific for P. acnes and do not seem to confer superinfection immunity.
Highlights
Propionibacterium acnes is a commensal of human skin but is known to be involved in certain diseases, such as acne vulgaris and infections of orthopaedic implants
Propionibacterium acnes is regarded as a commensal of human skin, but is known to be involved in different infections such as acne vulgaris [1] and infections with orthopaedic implants [2,3]
Prophages account for much of the genetic diversity seen in bacteria and often carry genes that are beneficial for the bacteria, including toxins and other virulence factors [16,17,18,19]
Summary
Propionibacterium acnes is a commensal of human skin but is known to be involved in certain diseases, such as acne vulgaris and infections of orthopaedic implants. Treatment of these conditions is complicated by increased resistance to antibiotics and/or biofilm formation of P. acnes bacteria. There have been reports about phages existing as extrachromosomal circular or linear plasmid prophages, as a part of their lysogenic cycle [13,14,15] These so called prophages become integrated parts of the genome and are replicated together with the bacterial genome during cell division. Prophages account for much of the genetic diversity seen in bacteria and often carry genes that are beneficial for the bacteria, including toxins and other virulence factors [16,17,18,19]
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