Quantitative real-time PCR detection of Propionibacterium acnes in archived prostate tissue

The Gram-positive skin commensal Propionibacterium acnes is an opportunistic pathogen associated with, for example, prosthetic joint failure, endocarditis, and ocular infections. P. acnes is frequently present in prostate tissue where it is significantly associated with acute and chronic inflammatory changes. These could potentially stimulate carcinogenesis. Current methods for P. acnes detection are sub-optimal due to slow growth of the organism in culture coupled with the lack of sensitivity of end-point PCRs for low level pathogen detection in clinical samples. We have developed a novel quantitative TaqMan® PCR assay to detect and quantify P. acnes specific 16S rRNA sequences. This assay is sensitive to ten genome equivalents when applied to pure cultures, and exhibits no cross-reactivity when tested against a specificity panel of over 50 species including common contaminants and other members of the Propionibacteriaceae. We have applied this assay to DNA extracted from archived prostate tissue specimens. Normalization with a human endogenous retrovirus-3 (ERV-3) assay has enabled comparison of cancerous prostate, non-cancerous prostate and ‘spiked’ prostate tissue controls. For comparison our assay has also been applied to other clinical samples including failed prosthetic joints, skin and other tissue controls. These data will be discussed in relation to clinical information.