CAMP factor homologues in Propionibacterium acnes: a new protein family differentially expressed by types I and II

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.

CAMP factor is not essential for systemic virulence of Group B Streptococcus

The Gram-positive pathogen Group B Streptococcus (GBS) is the leading cause of bacterial pneumonia, sepsis, and meningitis in human newborns. GBS elaborates a pore-forming toxin known as CAMP factor that synergizes with Staphylococcus aureus beta-toxin, generating a co-hemolytic reaction useful in identification of GBS in the clinical laboratory. To evaluate the indirect evidence implicating CAMP factor in GBS pathogenesis, the cfb gene encoding the pore-forming cytotoxin was deleted by precise allelic replacement. The virulence properties of the CAMP factor mutant were then explored by a series of in vitro and in vivo assays. Compared to wild-type, the isogenic GBS Deltacfb mutant demonstrated equivalent phagocyte resistance and endothelial cell invasiveness and also retained full virulence in a mouse model of infection. Our data suggest that CAMP factor expressed in its native context is not essential for systemic virulence of GBS.

Variable expression of immunoreactive surface proteins of Propionibacterium acnes

Despite accumulating data implicating Propionibacterium acnes in a variety of diseases, its precise role in infection remains to be determined. P. acnes antigen-specific CD4(+) T cells are present in early inflamed acne lesions and may be involved in the inflammatory response; however, little is known about the specific antigens involved. In this study, B cell and T cell antigens from P. acnes expression libraries were cloned and evaluated and the four predominant proteins identified were investigated. Two of these antigens share some homology with an M-like protein of Streptococcus equi and have dermatan-sulphate-binding activity (PA-25957 and 5541). The remaining two antigens, PA-21693 and 4687, are similar to the product of the Corynebacterium diphtheriae htaA gene from the hmu ABC transport locus, although only one of these (PA-21693) is encoded within an hmu-like operon and conserved amongst a range of clinical isolates. All four proteins contain an LPXTG motif, although only PA-21693 contains a characteristic sortase-sorting signal. Variation in the expression of PA-4687, 25957 and 5541 is evident amongst clinical isolates and is generated both by frameshifts associated with the putative signal peptide and by variable numbers of repeat regions toward the carboxy-terminus, potentially generating heterogeneity of molecular mass and antigenic variation. In addition, in the case of PA-25957, a frameshift in a C-rich region at the extreme carboxy-terminus eliminates the LPXTG motif in some isolates. For the dermatan-sulphate-binding PA-25957, IgG1 antibody in serum from acne-positive donors was shown to be specific for the amino-terminal region of the protein, which also contains a CD4(+) T cell epitope. In contrast, serum from acne-negative donors shows an IgG2 and IgG3 antibody subclass response to the carboxy-terminal region. These data have implications for the potential role of P. acnes in inflammatory acne and other diseases.

Polymerase chain reaction-based identification of Propionibacterium acnes types isolated from the male urinary tract: evaluation of adolescents, normal adults and men with prostatic pathology

OBJECTIVE

To assess whether colonization of the male urinary tract with Propionibacterium acnes, in particular types IB and II (which are associated with inflammation in radical prostatectomy specimens and might be involved in the development of prostate cancer), is associated with prostate disease, and thus to develop a urine test to detect men at risk of prostate disease.

PATIENTS, SUBJECTS AND METHODS

We developed the first polymerase chain reaction (PCR)-based technique for identifying P. acnes types IA, IB and II, and used this in combination with selective culture medium to compare the prevalence of these subtypes in the urinary tract of adolescent males, healthy adult men and patients with confirmed prostate pathology.

RESULTS

P. acnes types IB and II were no more prevalent in the urinary tract of patients with prostate pathology than in normal control men. However, the prevalence of types IB and II appeared to be higher in adult men (at 11 of 15 and six of 15, respectively) than in adolescents (two of six and one of six), suggesting an age-related increase. Comparison of urinary tract and facial skin P. acnes from three subjects showed that type IA was more often predominant on facial skin, whereas types IB or II were more often predominant in the urinary tract.

CONCLUSIONS

A urine test might not be useful for detecting men with prostatic P. acnes infection and thus at greater risk of associated prostate disease. However, this work validated our technique for detecting and identifying the three P. acnes subtypes, and identified some interesting trends worth further investigation.

Propionibacterium acnes and lipopolysaccharide induce the expression of antimicrobial peptides and proinflammatory cytokines/chemokines in human sebocytes

Acne is a common skin disorder of the pilosebaceous unit. In addition to genetic, hormonal and environmental factors, abnormal colonization by Propionibacterium acnes has been implicated in the occurrence of acne via the induction of inflammatory mediators. To gain more insight into the role that sebocytes play in the innate immune response of the skin, particularly in acne, we compared the antimicrobial peptide and proinflammatory cytokine/chemokine expression at mRNA and protein levels, as well as the viability and differentiation of SZ95 sebocytes in response to co-culture with representative isolates of P. acnes type IA and type IB as well as Escherichia coli-derived lipopolysaccharide (LPS). We found that, in vitro, P. acnes type IA and IB isolates and LPS induced human beta-defensin-2 and proinflammatory cytokine/chemokine expression, and influenced sebocyte viability and differentiation. Our results provide evidence that sebocytes are capable of producing proinflammatory cytokines/chemokines and antimicrobial peptides, which may have a role in acne pathogenesis. Furthermore, since P. acnes types IA and IB differentially affect both the differentiation and viability of sebocytes, our data demonstrate that different strains of P. acnes vary in their capacity to stimulate an inflammatory response within the pilosebaceous follicle.