Abstract: Viruses specifically infecting bacteria, or bacteriophages, are the most common biological entity in the biosphere. As such, they greatly influence bacteria, both in terms of enhancing their virulence and in terms of killing them. Since the first identification of bacteriophages in the beginning of the 20th century, researchers have been fascinated by these microorganisms and their ability to eradicate bacteria. In this review, we will cover the history of the Propionibacterium acnes bacteriophage research and point out how bacteriophage research has been an important part of the research on P. acnes itself. We will further discuss recent findings from phage genome sequencing and the identification of phage sequence signatures in clustered regularly interspaced short palindromic repeats (CRISPRs). Finally, the potential to use P. acnes bacteriophages as a therapeutic strategy to combat P. acnes-associated diseases will be discussed.
Abstract: <i>Propionibacterium acnes</i> is a Gram positive rod inhabiting the human skin that also infects orthopaedic implants and is associated with acne vulgaris. Previously, one lytic bacteriophage, PA6, from <i>P. acnes</i> has been sequenced and partially characterized. We recently isolated several inducible phages from <i>P. acnes</i> classified as Siphoviruses based on morphology and partial genome sequencing.
In this study we sequenced the inducible <i>P. acnes</i> phages PAD20 and PAS50, isolated from deep infection and from skin, respectively. The genomes of PAD20 and PAS50 are 29,074 and 29,017 bp, respectively, compared with the 29,739 bp of PA6. The phage genomes have 87.3-88.7% nucleotide sequence identity. The genes are divided into clusters with different levels of similarity between the phages. PAD20 and PAS50 share four genes encoding identical amino acid sequences. Some deletions and insertions in the genomes have occurred, resulting in lack of genes, frame shifts, and possible regulatory differences. No obvious virulence factor gene candidates were found. The phages are inducible, but bacteria can be cured of phages by serial colony isolations and lose their phages during stationary phase, but are still sensitive to new phage infections. Construction of a phylogenetic tree based on more than 459 phage genomes, suggested that <i>P. acnes</i> phages represent a new lineage of Siphoviruses.
The investigated <i>P. acnes</i> Siphovirus genomes share a high degree of homology to other <i>P. acnes</i> phages sequenced, but not to genomes of other phages isolated from Propionibacteria. The phage genomes are not integrated in the bacterial genome, but instead, most likely have a pseudolysogenic life cycle.
Abstract: <i>Finegoldia magna</i> is a member of the normal human bacterial flora on the skin and other non-sterile body surfaces, but this anaerobic coccus is also an important opportunistic pathogen. SufA was the first <i>F. magna</i> proteinase to be isolated and characterized. Many bacterial pathogens interfere with different steps of blood coagulation, and here we describe how purified SufA efficiently and specifically cleaves fibrinogen in human plasma. SufA is both secreted by <i>F. magna</i> and associated with the bacterial surface. Successful gene targeting has previously not been performed in anaerobic cocci, but in order to study the role of the SufA that is present at the bacterial surface, we constructed an <i>F. magna</i> mutant that expresses a truncated SufA lacking proteolytic activity. In contrast to wild-type bacteria that delayed the coagulation of human plasma, mutant bacteria had no such effect. Wild-type and mutant bacteria adhered to keratinocytes equally well, but in a plasma environment only wild-type bacteria blocked the formation of fibrin networks surrounding adherent bacteria. The effective cleavage of fibrinogen by SufA suggests that the interference with fibrin network formation represents an adaptive mechanism of <i>F. magna</i> with potential implications also for pathogenicity.
Abstract: <i>Propionibacterium acnes</i> is a common and probably underestimated cause of delayed joint prosthesis infection. Bacterial biofilm formation is central in the pathogenesis of infections related to foreign material, and <i>P. acnes</i> has been shown to form biofilm both <i>in vitro</i> and <i>in vivo</i>. Here, biofilm formation by 93 <i>P. acnes</i> isolates, either from invasive infections (n = 45) or from the skin of healthy people (n = 48), was analysed. The majority of isolates from deep infections produced biofilm in a microtitre model of biofilm formation, whereas the skin isolates were poor biofilm producers (p <0.001 for a difference). This indicates a role for biofilm formation in <i>P. acnes</i> virulence. The type distribution, as determined by sequencing of <i>recA</i>, was similar among isolates isolated from skin and from deep infections, demonstrating that <i>P. acnes</i> isolates with different genetic backgrounds have pathogenic potential. The biofilm formed on plastic and on bone cement was analysed by scanning electron microscopy (EM) and by transmission EM. The biofilm was seen as a 10-μm-thick layer covering the bacteria and was composed of filamentous as well as more amorphous structures. Interestingly, the presence of human plasma in solution or at the plastic surface inhibits biofilm formation, which could explain why <i>P. acnes</i> primarily infect plasma-poor environments of, for example, joint prostheses and cerebrospinal shunts. This work underlines the importance of biofilm formation in <i>P. acnes</i> pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of invasive <i>P. acnes</i> infections.
Abstract: <i>Propionibacterium acnes</i> 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 <i>P. acnes</i> bacteria. <i>P. acnes</i> 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 <i>P. acnes</i> on a genetic and morphological basis.
More than 70% (65/92) of <i>P. acnes</i> 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 <i>P. acnes</i> isolates from deep infections and isolates from skin. However, there was a significant lower carriage rate of phages in <i>P. acnes</i> 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 <i>P. acnes</i> isolates with inducible phages, but have less lytic activity against isolates that have no prophages. Phages only infected and lysed <i>P. acnes</i> 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 showed that the phages could be divided into different groups on a genetic basis.
Our findings indicate that temperate phages are common in <i>P. acnes</i>, and that they are a genetically and functionally homogeneous group of Siphoviruses. The phages are specific for <i>P. acnes</i> and do not seem to confer superinfection immunity.
