Cohen RJ et al. (2005) Propionibacterium acnes associated with inflammation in radical prostatectomy specimens: a possible link to cancer evolution? J Urol 173: 1969–1974

A research group has cultured Propionibacterium acnes from the prostates of men undergoing radical prostatectomy for carcinoma. P. acnes is a slow-growing organism that is rapidly overtaken by common microbes in standard laboratory culture; these features might explain why it has not previously been found in prostatic tissue.

Cancerous prostates often have multiple foci of acute and chronic inflammation, scattered throughout the organ rather than confined to tumor boundaries. The etiology of such inflammation is unknown, although its histologic resemblance to inflammation resulting from Helicobacter pylori infection in the stomach, a precursor of gastric carcinogenesis, has led to speculation that infectious agents might have a similar role in prostate carcinogenesis. Cohen et al. suggest that indolent but persistent infection with P. acnes could be a contributory factor.

Intact prostate glands were removed from 34 consecutive patients with localized cancer and processed within 30 min, taking care to avoid sites potentially exposed to surgical or skin contamination. Bacteria were found in 19 cases; P. acnes was predominant, occurring in 12 samples, and was the only organism to be associated with greater severity of inflammation. DNA typing and phenotypic analysis showed that all but two prostatic isolates of P. acnes differed from cutaneous isolates of this organism, suggesting that specific subtypes might be linked with inflammation.

Limitations of this study include the lack of control samples from healthy patients, and the observation that other, as yet unidentified, bacteria might be present. Further work should address these problems, and might lead to appropriate treatment.