Read condition-specific symptoms and clinical context for Cutibacterium acnes. The most abundant bacterium on healthy oily skin, and a contributor to skin balance rather than simply a cause of acne.
Rozas and colleagues describe C. acnes as the most abundant bacterium living in human, healthy and sebum-rich skin sites such as the face and the back, and as a commensal bacterium of human skin. It is a Gram-positive rod that is aerotolerant anaerobic and does not produce spores. It secretes a triacylglycerol lipase, GehA, to metabolise sebum, and predominantly produces propionic acid — the origin of its former genus name Propionibacterium — which contributes to maintaining the acidic layer on the skin’s surface. The species is diverse at subspecies and subtype level, with phylogenetic groups IA1, IA2, IB, IC, II and III. The review reports that loss of C. acnes relative abundance and clonal diversity is frequently associated with skin disorders including acne, atopic dermatitis, rosacea and psoriasis.
This profile describes a commensal bacterium of human skin, so no infection symptom list is assigned and none is invented. The bundled review describes C. acnes as the most abundant bacterium on healthy sebum-rich skin and reports that loss of its relative abundance or clonal diversity is frequently associated with skin disorders including acne, atopic dermatitis, rosacea and psoriasis — associations with conditions that have many causes, not symptoms caused by carrying this organism. Acne is a common inflammatory condition assessed by a clinician; this profile does not describe or diagnose it. The review also notes that systemic antibiotics aimed at reducing C. acnes can disrupt the skin equilibrium and may allow opportunistic follicle infection by competing species such as Pseudomonas, so reducing this organism is not automatically beneficial.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.