Staphylococcus epidermidis and Cutibacterium acnes: Two Major Sentinels of Skin Microbiota and the Influence of Cosmetics
It is apparent that Cutibacterium has two faces.
While the pathogenicity of this organism in shoulder periprosthetic infections has been emphasized, this review reminds us of the beneficial actions of this organism in fending off highly virulent organisms.
Cutibacterium are normally found in the pilosebaceous units of the chest and back. C. acnes growth areas correspond to environments rich in oleic and palmitic acids from sebum. The bacteria metabolizes fatty acids and other sebaceous fluids and lipids to generate free fatty acids, such as propionic and acetic acids. Cutibacterium participate in skin homeostasis, host defense and innate immunity helping the skin in fighting pathogenic bacteria by the direct inhibition of pathogen growth, competition for nutrients and occupation of an ecological niche. They can also directly kill pathogens by the production of bacteriocins and the induction of the production of antimicrobial peptides (cathelicidins and human beta defensins) by host cells, such as keratinocytes, sebocytes and immune cells. Bacteriocins produced by commensal C. acnes strains have in vitro an action directed against virulent pathogenic strains of Cutibacterium, lactic acid bacteria, Gram-negative bacteria and yeasts.
Shifts between commensalism and pathogenicity are commonly observed when the skin barrier is disturbed (drastic increase of skin pH, water loss, skin flaking, keratinocytes apoptosis and inflammation). Dysbiosis is a disequilibrium of microbiota diversity and functionality, often characterized by an abnormality in bacterial composition, abundance or deficiency. The relationship of cutaneous dysbiosis to periprosthetic infections is discussed in a recent article Preoperative Skin Cultures Predict Periprosthetic Infections in Revised Shoulder Arthroplasties When clinic skin cultures grew a high percentage (≥75%) of Cutibacterium this finding predicted a culture-positive Cutibacterium PJI with an accuracy of 94%. For male patients, a preoperative clinic skin Cutibacterium percentage of ≥75% predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 100%.
While there is some enthusiasm for altering the skin microbiome prior to surgery using agents such as Benzoyl Peroxide (BPO), it is possible that this intervention may open the door for more virulent organisms (see this link).
