Cutibacterium acnes (C. acnes) is a ubiquitous commensal bacterium that is generally well tolerated by the human skin immune system. Different strain-types of C. acnes have been reported to be enriched on patients with acne. To understand if these strain-type differences contribute to the develoment of inflammation we generated a library of over 400 C. acnes isolates from skin swabs of healthy and acne subjects and assessed their strain-level identity and inflammatory potential. A higher frequency of phylotype IA-1 C-type strains was observed from acne lesional sites compared to non-lesional sites. Phyotype II K-type sequences were dominant on healthy and non-lesional acne skin, but absent from lesions. Single locus sequence identity did not predict inflammatory potential as isolates within the same sequence type had different capacity to promote host cytokine responses in culture, or generate lesions in a mouse model. Inflammatory differences between strains was not due to protease or lipase activity, production of short chain fatty acids or porphyrins. Instead, whole genome sequencing of functionally distinct strains revealed the presence of a linear plasmid in the high cytokine-inducing strains. Mouse skin infected with similar sequence types of C. acnes with and without this plasmid resulted in differential activation of inflammatory genes in dermal fibroblasts as detected by single cell RNA sequencing. We conclude that C. acnes strain-type is not sufficient to predict inflammation but that other factors including the presence of a plasmid may contribute to development of disease.

ESDR349 - Functional screening of Cutibacterium acnes isolates reveal determinants of skin inflammation.

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.