Prosthetic Valve Endocarditis with Cutibacterium Acnes: A possible Contamination from the Sternal Skin Incision?

Background: Cutibacterium acnes (C. acnes), an anaerobic Gram-positive bacteria, and part of normal skin flora has been identified as a rare causative of infective endocarditis (IE). Especially in slow-growing microorganisms, such as C. acnes, routine practice of incubation may often lead to false negative results or be mistaken as skin contamination. Advanced microbiological methods such as Fluorescence In Situ Hybridization (FISH) facilitate the detection of causative agents for IE.

Methods: This retrospective single-center study was performed on a patient collective treated for valve endocarditis in the period from January 2016 to January 2023 in a single cardiosurgical institution. FISH in combination with 16S rRNA-gene PCR and sequencing (FISHseq) allowed visualization, identification and localization of active bacteria within explanted heart valve tissue sections.

Results: In 12 out of 308 patients C. acnes was identified as the causative agent of IE. All patients were male and all IEs were on prosthetic valves. The mean time from the previous surgical treatment to hospital admission was 61 months. 11 patients had biological and 1 patient had mechanical prostheses. FISHseq showed impressive biofilm formation and high activity of C. acnes in all of the cases. Additionally, in 3 cases tissue from the sternal scar of the previous operation was analyzed and detected with high density of active C. acnes around chest hair follicles.

Conclusion: C. acnes IE was solely found in patients with prosthetic valves, which implies possible contamination of the surgical site by skin incision during the primary surgery. A contamination was furthermore backed up by the finding that highly active C. acnes were detected around hair follicles in scar samples. The fact that the male gender was exclusively affected, could prove that body hair density and distribution are a risk factor for C. acnes IE. Last but not least, using a molecular technique (FISHseq) slow-growing and hard-detectable Cutibacterium spp. can reliably be identified.

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Artikel online veröffentlicht:
13. Februar 2024