Inhibitory Effect of Probiotic Metabolites on Seborrheic Dermatitis and Acne-Related Pathogenic Bacteria

The topical application of probiotic metabolites has shown positive effects in the treatment of skin diseases; however, the effectiveness is strain dependent. Comparing the pathogen inhibitory effects of probiotic strains with different genetic backgrounds and analyzing their key metabolites can provide insights about the potential of applying probiotics for skincare. In this study, we investigated the fermentation growth inhibition of 18 commercial probiotic strains on the skin pathogens Malassezia furfur (M. furfur) and Cutibacterium acnes (C. acnes) in vitro. We found that most Bifidobacterium animalis subsp. lactis (B. lactis) and Lacticaseibacillus rhamnosus (L. rhamnosus) strains exhibited strong inhibition of M. furfur and C. acnes, which lasted up to 100 h. The main antibacterial metabolites observed were molecules below 10,000 Da in molecular weight, including peptides and organic acids (lactic acid, acetic acid, propionic acid, and butyric acid). The synergistic effect of organic acid combinations lowered the minimum inhibitory concentration (MIC). The composition of these antimicrobial metabolites varied among strains, which demonstrated the strain-dependent pathogenic inhibitory effects. This study provides insights into the application potential of using probiotic metabolites against seborrheic dermatitis and acne-related pathogenic bacteria.