Probably less effective as a topical because of less penetration.
Topical Cutibacterium acnes May Reduce Comedones and Noninflamed Lesions in Mild to Moderate Acne
Topical application of Cutibacterium acnes , commensal bacteria, may be associated with reductions in comedone counts and noninflamed lesions in individuals with acne-prone skin, according to a small pilot study in Acta Dermato-Venereologica .
The open-label trial enrolled 14 otherwise healthy patients (age range, 18 to 23 years) with mild to moderate acne vulgaris. During an active induction phase, patients received 5% benzoyl peroxide gel for 7 days to deplete skin microflora. In the second 5-week interventional microbiome treatment phase, patients applied new C acnes strains to colonize skin.
Facial skin was assessed on day 1 to measure lesion count and pH and patients kept a daily diary to record activities that may have affected facial skin. Parameters of facial skin health were reassessed at day 7, and patients were randomly assigned to receive either 2 strains of C acnes Single Locus Sequence Typing [SLST] type C3 and K8 at 50% each (n=8) or 4 strains of C acnes SLST type C3 (55%), K8 (5%), A5 (30%), and F4 (10%) (n=6).
On day 7, there was an initial reduction in C acnes following application of the benzoyl peroxide gel and a subsequent increase in the bacteria by day 21 after application of the topical skin formulation. The overall percentage of C acnes was higher on day 21 (57.7%) and day 42 (50.9%) than day 1 (37.5%) and day 7 (32.4%). Both topical formulations were associated with reductions in non-inflamed lesions, including both open and closed comedones. No change was observed in the number of inflamed lesions, including papules and pustules
Study limitations included the small number of patients, the lack of a control group, and the short treatment duration.
The researchers wrote that there may “be some evidence that the modulation of strains may interfere with the follicular cast environment leading to the observed reduction in comedone formation.”