The Nesting Doll of Cutibacterium acnes Clonality.

In this issue of the Journal of Clinical Microbiology, R. E. Bumgarner, D. Harrison, and J. E. Hsu (J Clin Microbiol 58:e00121-19, 2020, https://doi.org/10.1128/JCM.00121-19) address in a retrospective analysis that clonality of Cutibacterium acnes isolates from deep tissue specimens obtained from patients during revision shoulder arthroplasty cannot be assumed. Given that multiple subtypes of C. acnes isolates are present on and around the skin pilosebaceous follicles, the finding of multiple subtypes in deep tissues around a single patient's infected joint is not entirely surprising. However, the authors also challenge laboratorians to consider whether further assessment of C. acnes isolates from the same joint should be performed and, if so, what testing should be undertaken.