Wednesday, December 4, 2013

Propionibacterium in failed shoulder arthroplasty - where do they come from? - how to best recover them?

Origin of Propionibacterium in Surgical Wounds and Evidence-Based Approach for Culturing Propionibacterium from Surgical Sites

Propionibacterium is commonly recovered from deep cultures obtained at the time of revision shoulder arthroplasty - even if the shoulder shows none of the characteristic clinical evidence of infection. The purpose of this study was to explore the origin of Propionibacterium in surgical wounds and to seek an optimized strategy for culturing this organism at the time of revision surgery.

Part I: In 23 of 30 volunteers, cultures taken from unprepared epidermis over the deltopectoral incisional area grew Propionibacterium. Cultures from males were more positive than those from females (p<.002)

Part II: In 41 patients having revision shoulder arthroplasty, only 1 of the 20 females had any positive culture while 12 males had positive dermal cultures and 12 had positive deep cultures - these two positive findings were significantly associated (p .0001).

 Part III: In the 74 shoulders with a Propionibacterium score>0.1, 372 cultures (average 5 per shoulder) were obtained of which 203 were positive. Cultures of component explants and soft tissues were positive in over half of the cases; fluid cultures were positive in only 40%. Anaerobic Brucella media were positive in 70%; aerobic and broth media were each positive in 52%. If only the Brucella media had been used, 30% of the 203 positive cultures would have been missed. The average time for the cultures to turn positive was 8.0 days +/- 4.7 days (range 1-25 days).

The chance of recovering Propionibacterium that are present in a surgical wound is optimized (95%) if (a) four different non-fluid specimens are obtained, (b) specimens are cultured on aerobic, anaerobic and broth media, and (c) the cultures are observed for a minimum of 17 days. 

Conclusion: Propionibacterium can often be cultured from deep specimens harvested at revision shoulder arthroplasty - especially in male patients - if appropriate methods are used. In that the surgical incision for arthroplasty must transect Propionibacterium–containing sebaceous glands and hair bulbs, the dermis is a likely source of this organism in deep wounds. Strategies for minimizing the risk of Propionibacterium infections need to be directed at reducing the contamination of surgical wounds from bacteria residing in as well as on the skin.

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