A groundbreaking study has shed new light on Cutibacterium acnes (C. acnes), the bacteria commonly associated with acne. While often blamed for breakouts, researchers have discovered that certain strains of this acne bacteria may play a protective role in skin health. The study, published in Microbiology Spectrum of the American Society for Microbiology, suggests that nonpathogenic strains of C. acnes can help the skin defend itself against Staphylococcus aureus (S. aureus), a bacteria known to cause infections.
A Closer Look at Acne Bacteria
For years, C. acnes has been considered a culprit behind acne, but recent advancements in gene sequencing have revealed that not all strains of the bacteria behave the same way. Researchers from Osaka City University and Okayama University used Caenorhabditis elegans (C. elegans), a tiny nematode, to explore the biological effects of different C. acnes strains. Unlike mammals, C. elegans provides a simple model for studying bacteria interactions while having a body barrier similar to human skin.
The study found that certain strains—specifically ribotype (RT) 4 and 8, which are often linked to acne—shortened the lifespan of the nematode. Meanwhile, RT6 strains, commonly found in people with healthy skin, had no such effect. This suggests that some strains of C. acnes contribute to acne, while others may be neutral or beneficial.
Boosting Skin’s Natural Defenses
The research team also examined whether beneficial strains of C. acnes could help protect against S. aureus infections. Their findings showed that nematodes exposed to healthy skin-associated strains of C. acnes survived longer when infected with S. aureus than those in the control group.
RNA sequencing analysis further revealed that these beneficial C. acnes strains activated genes linked to innate immunity and biological defense mechanisms in C. elegans. According to Professor Shuta Tomida of Okayama University Hospital, this protective effect is likely mediated through the TIR-1 and p38 MAPK pathways—key players in the body’s immune response.
Potential for New Probiotic Skin Treatments
These findings challenge the long-standing view of C. acnes as purely harmful and open the door for new skin treatments. By focusing on specific bacterial strains linked to clear skin, researchers hope to develop probiotic-based skincare solutions. Unlike traditional probiotics, which are often consumed, this approach could lead to a “non-drinking probiotic” that directly benefits skin health.
Professor Eriko Kage-Nakadai, an advisor to the study, emphasized the importance of evaluating bacteria at the strain level. “This reminds us that not all bacteria function the same way, even within the same species,” she said. Additionally, the study highlights C. elegans as a valuable alternative model for skin microbiome research, offering insights without the need for mammal testing.
With probiotic research largely dominated by Lactobacillus and Bifidobacteria, this study could pave the way for a new generation of skin-friendly bacterial treatments—changing how we think about acne bacteria and skin health.
Reference: Ayano Tsuru, Yumi Hamazaki, Shuta Tomida, Mohammad Shaokat Ali, Tomomi Komura, Yoshikazu Nishikawa, Eriko Kage-Nakadai. Nonpathogenic Cutibacterium acnes Confers Host Resistance against Staphylococcus aureus. Microbiology Spectrum, 2021
