Use of bacteriophage typing to distinguish Propionibacterium acne types I and II

NeoGenesis MB-1 with CRISPR Technology Reduces the Effects of the Viruses (Phages) Associated with Acne - Case Report

We present a case of acne successfully treated with a topical spray containing live bacteria. The live bacteria used in the spray contain CRISPR, and adaptive immune system in the bacteria that are used to disable viral replication. Because acne skin contains bacteria in the microbiome where a shift toward non-CRISPR bacteria occurs, these bacteria are susceptible to bacteriophage infection and lysogeny. Normalizing the bacterial microbiome to one containing more CRISPR-containing bacteria renormalizes the microbiome by killing inflammation-causing bacteriophage infecting the non-CRISPR bacteria associated with acne.

Carbon source competition within the wound microenvironment can significantly influence infection progression

It is becoming increasingly apparent that commensal skin bacteria have an important role in wound healing and infection progression. However, the precise mechanisms underpinning many of these probiotic interactions remain to be fully uncovered. In this work, we demonstrate that the common skin commensal Cutibacterium acnes can limit the pathogenicity of the prevalent wound pathogen Pseudomonas aeruginosa in vivo. We show that this impact on pathogenicity is independent of any effect on growth, but occurs through a significant downregulation of the Type Three Secretion System (T3SS), the primary toxin secretion system utilised by P. aeruginosa in eukaryotic infection. We also show a downregulation in glucose acquisition systems, a known regulator of the T3SS, suggesting that glucose availability in a wound can influence infection progression. C. acnes is well known as a glucose fermenting organism, and we demonstrate that topically supplementing a wound with glucose reverses the probiotic effects of C. acnes. This suggests that introducing carbon source competition within the wound microenvironment may be an effective way to prevent or limit wound infection.

The immunomodulatory potential of phage therapy to treat acne: a review on bacterial lysis and immunomodulation

Background

Characterized by an inflammatory pathogenesis, acne is the most common skin disorder worldwide. Altered sebum production, abnormal proliferation of keratinocytes, and microbiota dysbiosis represented by disbalance in Cutibacterium acnes population structure, have a synergic effect on inflammation of acne-compromised skin. Although the role of C. acnes as a single factor in acne development is still under debate, it is known that skin and skin-resident immune cells recognize this bacterium and produce inflammatory markers as a result. Control of the inflammatory response is frequently the target for acne treatment, using diverse chemical or physical agents including antibiotics. However, some of these treatments have side effects that compromise patient adherence and drug safety and in the case of antibiotics, it has been reported C. acnes resistance to these molecules. Phage therapy is an alternative to treat antibiotic-resistant bacterial strains and have been recently proposed as an immunomodulatory therapy. Here, we explore this perspective about phage therapy for acne, considering the potential immunomodulatory role of phages.

Methodology

Literature review was performed using four different databases (Europe PubMed Central-ePMC, Google Scholar, PubMed, and ScienceDirect). Articles were ordered and selected according to their year of publication, number of citations, and quartile of the publishing journal.

Results

The use of lytic bacteriophages to control bacterial infections has proven its promising results, and anti-inflammatory effects have been found for some bacteriophages and phage therapy. These effects can be related to bacterial elimination or direct interaction with immune cells that result in the regulation of pro-inflammatory cytokines. Studies on C. acnes bacteriophages have investigated their lytic activity, genomic structure, and stability on different matrices. However, studies exploring the potential of immunomodulation of these bacteriophages are still scarce.

Conclusions

C. acnes bacteriophages, as well as other phages, may have direct immunomodulatory effects that are yet to be fully elucidated. To our knowledge, to the date that this review was written, there are only two studies that investigate anti-inflammatory properties for C. acnes bacteriophages. In those studies, it has been evidenced reduction of pro-inflammatory response to C. acnes inoculation in mice after bacteriophage application. Nevertheless, these studies were conducted in mice, and the interaction with the immune response was not described. Phage therapy to treat acne can be a suitable therapeutic alternative to C. acnes control, which in turn can aid to restore the skin's balance of microbiota. By controlling C. acnes colonization, C. acnes bacteriophages can reduce inflammatory reactions triggered by this bacterium.

Cutibacterium acnes as an Opportunistic Pathogen: An Update of Its Virulence-Associated Factors

Cutibacterium acnes is a member of the skin microbiota found predominantly in regions rich in sebaceous glands. It is involved in maintaining healthy skin and has long been considered a commensal bacterium. Its involvement in various infections has led to its emergence as an opportunist pathogen. Interactions between C. acnes and the human host, including the human skin microbiota, promote the selection of C. acnes strains capable of producing several virulence factors that increase inflammatory capability. This pathogenic property may be related to many infectious mechanisms, such as an ability to form biofilms and the expression of putative virulence factors capable of triggering host immune responses or enabling C. acnes to adapt to its environment. During the past decade, many studies have identified and characterized several putative virulence factors potentially involved in the pathogenicity of this bacterium. These virulence factors are involved in bacterial attachment to target cells, polysaccharide-based biofilm synthesis, molecular structures mediating inflammation, and the enzymatic degradation of host tissues. C. acnes, like other skin-associated bacteria, can colonize various ecological niches other than skin. It produces several proteins or glycoproteins that could be considered to be active virulence factors, enabling the bacterium to adapt to the lipophilic environment of the pilosebaceous unit of the skin, but also to the various organs it colonizes. In this review, we summarize current knowledge concerning characterized C. acnes virulence factors and their possible implication in the pathogenicity of C. acnes.

Phages and their potential to modulate the microbiome and immunity

Bacteriophages (hence termed phages) are viruses that target bacteria and have long been considered as potential future treatments against antibiotic-resistant bacterial infection. However, the molecular nature of phage interactions with bacteria and the human host has remained elusive for decades, limiting their therapeutic application. While many phages and their functional repertoires remain unknown, the advent of next-generation sequencing has increasingly enabled researchers to decode new lytic and lysogenic mechanisms by which they attack and destroy bacteria. Furthermore, the last decade has witnessed a renewed interest in the utilization of phages as therapeutic vectors and as a means of targeting pathogenic or commensal bacteria or inducing immunomodulation. Importantly, the narrow host range, immense antibacterial repertoire, and ease of manipulating phages may potentially allow for their use as targeted modulators of pathogenic, commensal and pathobiont members of the microbiome, thereby impacting mammalian physiology and immunity along mucosal surfaces in health and in microbiome-associated diseases. In this review, we aim to highlight recent advances in phage biology and how a mechanistic understanding of phage-bacteria-host interactions may facilitate the development of novel phage-based therapeutics. We provide an overview of the challenges of the therapeutic use of phages and how these could be addressed for future use of phages as specific modulators of the human microbiome in a variety of infectious and noncommunicable human diseases.

Propionibacterium acnes and Acne Vulgaris: New Insights from the Integration of Population Genetic, Multi-Omic, Biochemical and Host-Microbe Studies

The anaerobic bacterium Propionibacterium acnes is believed to play an important role in the pathophysiology of the common skin disease acne vulgaris. Over the last 10 years our understanding of the taxonomic and intraspecies diversity of this bacterium has increased tremendously, and with it the realisation that particular strains are associated with skin health while others appear related to disease. This extensive review will cover our current knowledge regarding the association of P. acnes phylogroups, clonal complexes and sequence types with acne vulgaris based on multilocus sequence typing of isolates, and direct ribotyping of the P. acnes strain population in skin microbiome samples based on 16S rDNA metagenomic data. We will also consider how multi-omic and biochemical studies have facilitated our understanding of P. acnes pathogenicity and interactions with the host, thus providing insights into why certain lineages appear to have a heightened capacity to contribute to acne vulgaris development, while others are positively associated with skin health. We conclude with a discussion of new therapeutic strategies that are currently under investigation for acne vulgaris, including vaccination, and consider the potential of these treatments to also perturb beneficial lineages of P. acnes on the skin.

Propionibacterium (Cutibacterium) acnes Bacteriophage Therapy in Acne: Current Evidence and Future Perspectives

Acne vulgaris is the most common dermatological disorder worldwide. It is a multifactorial disease that involves increased sebum production, hyperkeratinization of the pilosebaceous unit, Propionibacterium acnes (Cutibacterium acnes) colonization, and inflammation. The human skin microbiome hosts a wide variety of microorganisms, including bacteria, viruses, and fungi. A delicate balance of these microorganisms is essential for the barrier function of the skin. Propionibacterium acnes represents nearly 90% of the human skin microbiome of healthy adults. Acne is a chronic recurrent disease that requires long-lasting treatment, which has led to the emergence of antibiotic resistance. New alternatives to traditional therapy are emerging, including antimicrobial peptides, natural engineered antibodies, and bacteriophages. Bacteriophages have been shown to play a role in human skin health and disease. There is evidence supporting phage therapy in many types of skin infections. P. acnes bacteriophages have been isolated and characterized. However, only a few in vitro studies have tested the ability of bacteriophages to kill P. acnes. Furthermore, there is no evidence on bacteriophage therapy in the treatment of acne in humans. In this review, we summarize the most recent evidence regarding P. acnes bacteriophages and the potential role of these bacteriophages in the treatment of acne. Further research on this field will provide the evidence to use phage therapy to decrease rates of antibiotic resistance and restore antibiotic susceptibility of P. acnes.

Host-microbiome interactions and recent progress into understanding the biology of acne vulgaris

Acne is one of the most common skin diseases worldwide and results in major health care costs and significant morbidity to severely affected individuals. However, the pathophysiology of this disorder is not well understood. Host-microbiome interactions that affect both innate and adaptive immune homeostasis appear to be a central factor in this disease, with recent observations suggesting that the composition and activities of the microbiota in acne is perturbed. Staphylococcus epidermidis and Cutibacterium acnes (C. acnes; formerly Propionibacterium acnes) are two major inhabitants of the skin that are thought to contribute to the disease but are also known to promote health by inhibiting the growth and invasion of pathogens. Because C. acnes is ubiquitous in sebaceous-rich skin, it is typically labeled as the etiological agent of acne yet it fails to fulfill all of Koch's postulates. The outdated model of acne progression proposes that increased sebum production promotes over-proliferation of C. acnes in a plugged hair follicle, thereby driving inflammation. In contrast, growing evidence indicates that C. acnes is equally abundant in both unaffected and acne-affected follicles. Moreover, recent advances in metagenomic sequencing of the acne microbiome have revealed a diverse population structure distinct from healthy individuals, uncovering new lineage-specific virulence determinants. In this article, we review recent developments in the interactions of skin microbes with host immunity, discussing the contribution of dysbiosis to the immunobiology of acne and newly emerging skin microbiome-based therapeutics to treat acne.

Over a Decade of recA and tly Gene Sequence Typing of the Skin Bacterium Propionibacterium acnes: What Have We Learnt?

The Gram-positive, anaerobic bacterium Propionibacterium acnes forms part of the normal microbiota on human skin and mucosal surfaces. While normally associated with skin health, P. acnes is also an opportunistic pathogen linked with a range of human infections and clinical conditions. Over the last decade, our knowledge of the intraspecies phylogenetics and taxonomy of this bacterium has increased tremendously due to the introduction of DNA typing schemes based on single and multiple gene loci, as well as whole genomes. Furthermore, this work has led to the identification of specific lineages associated with skin health and human disease. In this review we will look back at the introduction of DNA sequence typing of P. acnes based on recA and tly loci, and then describe how these methods provided a basic understanding of the population genetic structure of the bacterium, and even helped characterize the grapevine-associated lineage of P. acnes, known as P. acnes type Zappe, which appears to have undergone a host switch from humans-to-plants. Particular limitations of recA and tly sequence typing will also be presented, as well as a detailed discussion of more recent, higher resolution, DNA-based methods to type P. acnes and investigate its evolutionary history in greater detail.

Cutibacterium (formerly Propionibacterium) acnes infections associated with implantable devices

INTRODUCTION

Cutibacterium acnes (C. acnes), a Gram-positive biofilm-forming rod implicated in acne vulgaris, is increasingly recognized for its role in implant-associated infections. The diagnosis of C. acnes implant-associated infections remains challenging. The optimal treatment is a combination of both surgical intervention and antibiotic therapy. Areas covered: In this review, we discuss the different types of implant-associated infections caused by C. acnes. We also highlight the clinical manifestations pertaining to the various sites of infection, and identify several risk factors previously reported in the literature. We then cover the diagnostic laboratory markers, such as IL-6 and AD-1, optimizing C. acnes recovery in culture, and the specific molecular techniques. Finally, we examine the various effective antibiotic regimens and identify some preventive methods against C. acnes infections. Expert commentary: Biomarkers such as IL-6 and AD-1 should be further investigated for the diagnosis of C. acnes implant-associated infections. The use of 16S rRNA gene sequencing and other molecular techniques should be further explored in this setting. Longer incubation periods should be requested whenever C. acnes infection is suspected. If the clinical suspicion is high, sonication of the excised implant should be encouraged. Research should focus on developing effective anti-biofilm agents. Finally, preventive methods such as hair removal prior to surgery should be further explored.

Optimization of genotypic and biochemical methods to profile P. acnes isolates from a patient population

Propionibacterium acnes is a key factor in the pathogenesis of acne vulgaris, although currently it is also being associated with medical-device infections. The aim of this work was to validate a safe and quick identification and typing of 24 clinical isolates of Propionibacterium acnes, applying a range of biochemical as well as genetic methods, and investigating the pathogenic potential to associate the different types with human health. RAPD-PCRs revealed the existence of two discernible clusters in correspondence with the phylogroups I and II, according to the PAtig gene polymorphism, leading them to be assigned as P. acnes subsp. acnes subsp. nov. Biotyping according to the pattern of sugar fermentation evidenced that all the isolates from acne and the majority from opportunistic infections fit the biotype I-B3. Consistent with the multiplex touchdown analysis, nearly all the isolates included in this biotype belonged to the subgroups IA1 (the exception being four strains classified as IB). The remaining ones were assigned to phylogroup II, considered to be part of the normal cutaneous microbiota. The susceptibility to three antibiotics was also investigated to explore the relations with the virulence, although no clear trend was identified.

Prospects of Phage Application in the Treatment of Acne Caused by Propionibacterium acnes

Propionibacterium acnes is associated with purulent skin infections, and it poses a global problem for both patients and doctors. Acne vulgaris (acne) remains a problem due to its chronic character and difficulty of treatment, as well as its large impact on patients' quality of life. Due to the chronic course of the disease, treatment is long lasting, and often ineffective. Currently there are data regarding isolation of P. acnes phages, and there have been numerous studies on phage killing of P. acnes, but no data are available on phage application specifically in acne treatment. In this review, we have summarized the current knowledge on the phages active against P. acnes described so far and their potential application in the treatment of acne associated with P. acnes. The treatment of acne with phages may be important in order to reduce the overuse of antibiotics, which are currently the main acne treatment. However, more detailed studies are first needed to understand phage functioning in the skin microbiome and the possibility to use phages to combat P. acnes.

Understanding the role of Propionibacterium acnes in acne vulgaris: The critical importance of skin sampling methodologies

Acne vulgaris is a chronic inflammatory skin condition classified by the Global Burden of Disease Study as the eighth most prevalent disease worldwide. The pathophysiology of the condition has been extensively studied, with an increase in sebum production, abnormal keratinization of the pilosebaceous follicle, and an inflammatory immune response all implicated in its etiology. One of the most disputed points, however, is the role of the gram-positive anaerobic bacterium Propionibacterium acnes in the development of acne, particularly when this organism is also found in normal sebaceous follicles of healthy skin. Against this background, we now describe the different sampling strategies that have been adopted for qualitative and quantitative study of P acnes within intact hair follicles of the skin and discuss the strengths and weaknesses of such methodologies for investigating the role of P acnes in the development of acne.

Emendation of Propionibacterium acnes subsp. acnes (Deiko et al. 2015) and proposal of Propionibacterium acnes type II as Propionibacterium acnes subsp. defendens subsp. nov

Recently, it has been proposed that strains of Propionibacterium acnes from the type III genetic division should be classified as P. acnessubsp. elongatum subsp. nov., with strains from the type I and II divisions collectively classified as P. acnessubsp. acnes subsp. nov. Under such a taxonomic re-appraisal, we believe that types I and II should also have their own separate rank of subspecies. In support of this, we describe a polyphasic taxonomic study based on the analysis of publicly available multilocus and whole-genome sequence datasets, alongside a systematic review of previously published phylogenetic, genomic, phenotypic and clinical data. Strains of types I and II form highly distinct clades on the basis of multilocus sequence analysis (MLSA) and whole-genome phylogenetic reconstructions. In silico or digital DNA-DNA similarity values also fall within the 70-80 % boundary recommended for bacterial subspecies. Furthermore, we see important differences in genome content, including the presence of an active CRISPR/Cas system in type II strains, but not type I, and evidence for increasing linkage equilibrium within the separate divisions. Key biochemical differences include positive test results for β-haemolytic, neuraminidase and sorbitol fermentation activities with type I strains, but not type II. We now propose that type I strains should be classified as P. acnessubsp. acnes subsp. nov., and type II as P. acnessubsp. defendens subsp. nov. The type strain of P. acnessubsp. acnes subsp. nov. is NCTC 737T (=ATCC 6919T=JCM 6425T=DSM 1897T=CCUG 1794T), while the type strain of P. acnessubsp. defendens subsp. nov. is ATCC 11828 (=JCM 6473=CCUG 6369).

The diversity and host interactions of Propionibacterium acnes bacteriophages on human skin

The viral population, including bacteriophages, is an important component of the human microbiota, yet is poorly understood. We aim to determine whether bacteriophages modulate the composition of the bacterial populations, thus potentially playing a role in health or disease. We investigated the diversity and host interactions of the bacteriophages of Propionibacterium acnes, a major human skin commensal implicated in acne pathogenesis. By sequencing 48 P. acnes phages isolated from acne patients and healthy individuals and by analyzing the P. acnes phage populations in healthy skin metagenomes, we revealed that P. acnes phage populations in the skin microbial community are often dominated by one strain. We also found phage strains shared among both related and unrelated individuals, suggesting that a pool of common phages exists in the human population and that transmission of phages may occur between individuals. To better understand the bacterium-phage interactions in the skin microbiota, we determined the outcomes of 74 genetically defined Propionibacterium strains challenged by 15 sequenced phages. Depending on the Propionibacterium lineage, phage infection can result in lysis, pseudolysogeny, or resistance. In type II P. acnes strains, we found that encoding matching clustered regularly interspaced short palindromic repeat spacers is insufficient to confer phage resistance. Overall, our findings suggest that the prey-predator relationship between bacteria and phages may have a role in modulating the composition of the microbiota. Our study also suggests that the microbiome structure of an individual may be an important factor in the design of phage-based therapy.

Typing of Propionibacterium acnes: a review of methods and comparative analysis

Propionibacterium acnes is a major commensal of the human skin. However, it is also the pathogen responsible for acne vulgaris and other diseases, such as medical-device infections. Strains of Propionibacterium acnes have long been classified into several different types. Recently, typing systems for this bacterium have taken on an increased importance as different types of P. acnes have been found to be associated with different disease states, including acne. Genetic approaches based on individual or multiple genes have classified P. acnes into types, which have been supported by the sequencing of nearly 100 P. acnes genomes. These types have distinct genetic, transcriptomic and proteomic differences. Additionally, they may have different immune response profiles. Taken together, these factors may account for the different disease associations of P. acnes types.

Bacteriophages infecting Propionibacterium acnes

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.

Propionibacterium acnes bacteriophages display limited genetic diversity and broad killing activity against bacterial skin isolates

Investigation of the human microbiome has revealed diverse and complex microbial communities at distinct anatomic sites. The microbiome of the human sebaceous follicle provides a tractable model in which to study its dominant bacterial inhabitant, Propionibacterium acnes, which is thought to contribute to the pathogenesis of the human disease acne. To explore the diversity of the bacteriophages that infect P. acnes, 11 P. acnes phages were isolated from the sebaceous follicles of donors with healthy skin or acne and their genomes were sequenced. Comparative genomic analysis of the P. acnes phage population, which spans a 30-year temporal period and a broad geographic range, reveals striking similarity in terms of genome length, percent GC content, nucleotide identity (>85%), and gene content. This was unexpected, given the far-ranging diversity observed in virtually all other phage populations. Although the P. acnes phages display a broad host range against clinical isolates of P. acnes, two bacterial isolates were resistant to many of these phages. Moreover, the patterns of phage resistance correlate closely with the presence of clustered regularly interspaced short palindromic repeat elements in the bacteria that target a specific subset of phages, conferring a system of prokaryotic innate immunity. The limited diversity of the P. acnes bacteriophages, which may relate to the unique evolutionary constraints imposed by the lipid-rich anaerobic environment in which their bacterial hosts reside, points to the potential utility of phage-based antimicrobial therapy for acne.

IMPORTANCE

Propionibacterium acnes is a dominant member of the skin microflora and has also been implicated in the pathogenesis of acne; however, little is known about the bacteriophages that coexist with and infect this bacterium. Here we present the novel genome sequences of 11 P. acnes phages, thereby substantially increasing the amount of available genomic information about this phage population. Surprisingly, we find that, unlike other well-studied bacteriophages, P. acnes phages are highly homogeneous and show a striking lack of genetic diversity, which is perhaps related to their unique and restricted habitat. They also share a broad ability to kill clinical isolates of P. acnes; phage resistance is not prevalent, but when detected, it appears to be conferred by chromosomally encoded immunity elements within the host genome. We believe that these phages display numerous features that would make them ideal candidates for the development of a phage-based therapy for acne.

Characterization and genome sequencing of two Propionibacterium acnes phages displaying pseudolysogeny

Background

Propionibacterium acnes 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 P. acnes has been sequenced and partially characterized. We recently isolated several inducible phages from P. acnes classified as Siphoviruses based on morphology and partial genome sequencing.

Results

In this study we sequenced the inducible P. acnes 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 P. acnes phages represent a new lineage of Siphoviruses.

Conclusions

The investigated P. acnes Siphovirus genomes share a high degree of homology to other P. acnes 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.

Inducible Siphoviruses in superficial and deep tissue isolates of Propionibacterium acnes

BACKGROUND

Propionibacterium 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.

RESULTS

More 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.

CONCLUSION

Our 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.

A new phylogenetic group of Propionibacterium acnes

Immunofluorescence microscopy-based identification of presumptive Propionibacterium acnes isolates, using the P. acnes-specific mAb QUBPa3, revealed five organisms with an atypical cellular morphology. Unlike the coryneform morphology seen with P. acnes types I and II, these isolates exhibited long slender filaments (which formed large tangled aggregates) not previously described in P. acnes. No reaction with mAbs that label P. acnes types IA (QUBPa1) and II (QUBPa2) was observed. Nucleotide sequencing of the 16S rRNA gene (1484 bp) revealed the isolates to have between 99.8 and 99.9 % identity to the 16S rRNA gene of the P. acnes type IA, IB and II strains NCTC 737, KPA171202 and NCTC 10390, respectively. Analysis of the recA housekeeping gene (1047 bp) did reveal, however, a greater number of conserved nucleotide polymorphisms between the sequences from these isolates and those from NCTC 737 (98.9 % identity), KPA171202 (98.9 % identity) and NCTC 10390 (99.1 % identity). Phylogenetic investigations demonstrated that the isolates belong to a novel recA cluster or lineage distinct from P. acnes types I and II. We now propose this new grouping as P. acnes type III. The prevalence and clinical importance of this novel recA lineage amongst isolates of P. acnes remains to be determined.

Genome sequence and analysis of a Propionibacterium acnes bacteriophage

Cutaneous propionibacteria are important commensals of human skin and are implicated in a wide range of opportunistic infections. Propionibacterium acnes is also associated with inflammatory acne vulgaris. Bacteriophage PA6 is the first phage of P. acnes to be sequenced and demonstrates a high degree of similarity to many mycobacteriophages both morphologically and genetically. PA6 possesses an icosahedreal head and long noncontractile tail characteristic of the Siphoviridae. The overall genome organization of PA6 resembled that of the temperate mycobacteriophages, although the genome was much smaller, 29,739 bp (48 predicted genes), compared to, for example, 50,550 bp (86 predicted genes) for the Bxb1 genome. PA6 infected only P. acnes and produced clear plaques with turbid centers, but it lacked any obvious genes for lysogeny. The host range of PA6 was restricted to P. acnes, but the phage was able to infect and lyse all P. acnes isolates tested. Sequencing of the PA6 genome makes an important contribution to the study of phage evolution and propionibacterial genetics.

Propionibacterium acnes

Propionibacterium acnes, a common skin organism, is most notably recognized for its role in acne vulgaris. It also causes postoperative and device-related infections and has been associated with a number of other conditions such as sarcoidosis and synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO), although its precise role as a causative agent remains to be determined. Propionibacterium acnes produces a number of virulence factors and is well known for its inflammatory and immunomodulatory properties. Recent publication of the P. acnes genome should provide further insights into the pathogenic capabilities of the organism and potentially lead to the development of new therapies.

Propionibacterium acnes types I and II represent phylogenetically distinct groups

Although two phenotypes of the opportunistic pathogen Propionibacterium acnes (types I and II) have been described, epidemiological investigations of their roles in different infections have not been widely reported. Using immunofluorescence microscopy with monoclonal antibodies (MAbs) QUBPa1 and QUBPa2, specific for types I and II, respectively, we investigated the prevalences of the two types among 132 P. acnes isolates. Analysis of isolates from failed prosthetic hip implants (n = 40) revealed approximately equal numbers of type I and II organisms. Isolates from failed prosthetic hip-associated bone (n = 6) and tissue (n = 38) samples, as well as isolates from acne (n = 22), dental infections (n = 8), and skin removed during surgical incision (n = 18) were predominately of type I. A total of 11 (8%) isolates showed atypical MAb labeling and could not be conclusively identified. Phylogenetic analysis of P. acnes by nucleotide sequencing revealed the 16S rRNA gene to be highly conserved between types I and II. In contrast, sequence analysis of recA and a putative hemolysin gene (tly) revealed significantly greater type-specific polymorphisms that corresponded to phylogenetically distinct cluster groups. All 11 isolates with atypical MAb labeling were identified as type I by sequencing. Within the recA and tly phylogenetic trees, nine of these isolates formed a cluster distinct from other type I organisms, suggesting a further phylogenetic subdivision within type I. Our study therefore demonstrates that the phenotypic differences between P. acnes types I and II reflect deeper differences in their phylogeny. Furthermore, nucleotide sequencing provides an accurate method for identifying the type status of P. acnes isolates.

First evidence of lysogeny in Propionibacterium freudenreichii subsp. shermanii

Dairy propionic acid bacteria, particularly the species Propionibacterium freudenreichii, play a major role in the ripening of Swiss type cheese. Isometric and filamentous bacteriophages infecting P. freudenreichii have previously been isolated from cheese. In order to determine the origin of these bacteriophages, lysogeny of P. freudenreichii was determined by isometric bacteriophage type analysis. The genomic DNA of 76 strains were hybridized with the DNA of nine bacteriophages isolated from Swiss type cheeses, and the DNA of 25 strains exhibited strong hybridization. Three of these strains released bacteriophage particules following UV irradiation (254 nm) or treatment with low concentrations of mitomycin C. A prophage-cured derivative of P. freudenreichii was readily isolated and subsequently relysogenized. Lysogeny was therefore formally demonstrated in P. freudenreichii.

Sub-species discrimination, using pyrolysis mass spectrometry and self-organising neural networks, of Propionibacterium acnes isolated from normal human skin

Curie-point pyrolysis mass spectra were obtained from 30 Propionibacterium acnes strains isolated from the foreheads of six healthy humans. Multivariate analyses and Kohonen artificial neural networks (KANNs), employing unsupervised learning, were used successfully to discriminate between the P.acnes isolates from different individual hosts. The classification of the isolates by KANNs was compared with the more classical multivariate techniques of canonical variates analysis and hierarchical cluster analysis and found to give similar groupings. The combination of pyrolysis mass spectrometry with these numerical methods also showed that more than one strain of P.acnes had been isolated from three of the human hosts.

Occurrence of Propionibacterium freudenreichii bacteriophages in swiss cheese

We isolated bacteriophages active against Propionibacterium freudenreichii from 16 of 32 swiss cheese samples. Bacteriophage concentrations ranged from 14 to 7 x 10(5) PFU/g, depending on the sample and the sensitive strain used for detection. Only a few strains, 8 of the 44 strains of P. freudenreichii in our collection, were sensitive. We observed that multiplication of bacteriophages occurred in the cheese loaf during multiplication of propionibacteria in a warm curing room, but it seems that these bacteriophages have no adverse effect on the development of the propionic flora. We also found that sensitive cells, originating from either the starter or the cheese-making milk, were present at a high level (10(9) CFU/g) in the cheese.

Activation of the alternative pathway of complement in human serum by Propionibacterium acnes (Corynebacterium parvum) cell fractions

Activation of the alternative pathway of complement is known to be initiated by bacterial structures. We have fractionated Propionibacterium acnes cells, purified various cell fractions, and tested their complement-activating ability in human serum chelated with ethyleneglycol bis-(beta-aminoethylether)-N,N1-tetraacetic acid. The majority of complement-activating activity was localized in the wall fraction. This activity was resistant to lipid extraction, protease, RNAse, DNAse and lysozyme treatment. NaIO4, formamide, and hot (but not cold) trichloroacetic acid (TCA) extraction ablated the complement-activating capacity of cell walls. Compounds removed by extraction failed to consume significant hemolytic activity against antibody-coated sheep erythrocytes (EA). Addition of TCA-extracted soluble material to cell wall suspensions resulted in an inhibition of hemolytic consumption by the cell wall. These results indicate that, in P. acnes, complement-activating molecules are located in the cell wall and are carbohydrate in nature. Peptidoglycan, lipid, protein, and nucleic acid do not appear to contribute to the cell wall's ability to activate complement.

Polymorphonuclear leukocyte lysosomal release in response to Propionibacterium acnes in vitro and its enhancement by sera from inflammatory acne patients

Propionibacterium acnes cells were tested for the ability to trigger lysosomal hydrolase release from human polymorphonuclear leukocytes. Representative strains of P. acnes serotype I and II failed to stimulate lysosomal release in the absence of serum. P. acnes growth culture supernatants failed to trigger release under any test condition. Addition of fresh or heat-inactivated human serum resulted in lysosomal hydrolase release directly proportional to the number of P. acnes/PMN. Pooled sera from acne patients, with a high anti-P. acnes titer stimulated release to P. acnes. Preabsorption of this reagent with P. acnes cells reduced the anti-P. acnes titer and produced 93.37 +/- 11.49% inhibition of lysosomal enzyme release compared to unabsorbed anti-serum. Electron microscopy indicated that P. acnes was readily phagocytosed by PMNs when fresh or heated serum was present.

Biotyping of Propionibacterium acnes isolated from normal human facial skin

Biochemical and serological characteristics of 128 strains of Propionibacterium acnes isolated from the facial skin of healthy Japanese volunteers were compared with the three standard strains of the American Type Culture Collection, ATCC 6919, 11827, and 11828. Accordingly, the isolated strains of P. acnes were classified into five biotypes (B1 to B5) on the basis of fermentation tests of ribose, erythritol, and sorbitol. Two serotypes were distinguished by the agglutination test. P. acnes belonging to serotype I had galactose as a cell wall sugar, whereas those of serotype II lacked galactose. The strains of serotype I were distributed among all five biotypes (B1 to B5); however, those of serotype II consisted only of one biotype (B2). A term "sero-biotype" was introduced to differentiate and carefully classify the isolates. The predominant sero-biotypes differed with the individual and region of the facial skin. In general, strains of sero-biotype IB1, IB3, IB4, and IIB2 were more frequently isolated than those of sero-biotype IB2 and IB5. Thus, for routine assay work, serotyping of P. acnes as based on erythritol and sorbitol fermentation is both practical and applicable.

Complement activation in acne vulgaris: in vitro studies with Propionibacterium acnes and Propionibacterium granulosum

To better define the role of bacteria in inflammatory acne vulgaris, we have investigated the ability of four strains of Propionibacterium acnes and three strains of Propionibacterium granulosum to activate complement. Complement activation was assayed by incubating normal human serum with varying concentrations of each strain and measuring residual total hemolytic complement activity. When serum was tested unaltered, P. acnes strains were approximately threefold more potent than an equal weight of P. granulosum in consuming complement, which could reflect classical and/or alternative pathway activation. All strains also consumed complement in serum chelated with ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid, which selectively assays alternative pathway activation. Incubation of unaltered serum with both P. acnes and P. granulosum resulted in immunoelectrophoretic conversion of C4, C3, and factor B of the alternative pathway. Incubation of chelated serum resulted in conversion of C3 and factor B. These data taken together suggest that both species can activate complement through either pathway. Serum incubated with P. acnes was chemotactic for polymorphonuclear leukocytes, and this chemotactic activity was largely C5 dependent as shown by antibody inhibition. It is suggested that complement activation may occur in vivo in acne, and the inflammatory response may be contributed to by the generation of C5-dependent chemotactic factors.