“Since P. acnes forms part of the normal flora of the skin, it is important to identify specific subtypes of the bacterium that have specific capacity to colonize the prostatic tissue and trigger an inflammatory response over a prolonged time,” said Dr Davidsson. “If the involvement of specific subtypes of P. acnes can be shown, vaccination therapies may be feasible.”

“The rapid development of different techniques to identify and characterize infectious agents will help us to identify new viruses and bacteria that may have a role in cancer development,” said Dr Davidsson, adding that these agents could play a role “either through the extrinsic or intrinsic pathway.”

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The authors wrote that the mechanism by which P. acnes contributes to prostate carcinogenesis, while not understood, may also include factors other than inflammation. They referred to a recent in vitro study, which found that exposure to the bacterium “enabled anchorage-independent growth,” an indicator of tumorigenicity.2

“We believe that these results may be of importance in future work trying to individualize prostate cancer treatment, with the aim of improving the quality of life in prostate cancer patients,” said Dr Davidsson. “In clinical practice, patients with prostatic tissue positive for chronic inflammation and P. acnes may be considered high risk for prostate cancer development. This may indicate the need of preventive strategies, such as anti-inflammatory drugs.”

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Dr Davidsson said her team plans to investigate whether specific subtypes of P. acnes that have a higher propensity to colonize the prostate gland exist in prostate tissue.

“We will also initiate a study to investigate the temporality of P. acnes infection with respect to prostate cancer,” she said. “Future studies should address the question of whether prostatic-specific subtypes of P. acnes exist, which are more prone to cause infections than others.”


  1. Davidsson S, Molling P, Rider JR, et al. Frequency and typing of Propionibacterium acnes in prostate tissue obtained from men with and without prostate cancer. 9 Jun 2016. Infect Agent Cancer. doi: 10.1186/s13027-016-0074-9 [Epub ahead of print]
  2. Fassi FL, Mak TN, Laube B, et al. Prevalence of Propionibacterium acnes in diseased prostates and its inflammatory and transforming activity on prostate epithelial cells. Int J Med. 2011;301(1):69-78.