Microbial community structure in tinea corporis and antifungal activity of Lactiplantibacillus plantarum YM-4-3 strain.

OBJECTIVE: Tinea corporis is a common superficial fungal infection associated with skin microbiota dysbiosis. This study aimed to investigate the microbial community structure in lesional and peri-lesional skin of tinea corporis patients and to evaluate the antifungal activity of a probiotic Lactiplantibacillus plantarum strain against dermatophytes and Candida albicans. METHODS: Fifty skin-scraping samples were collected from 25 tinea corporis patients (paired lesional and adjacent non-lesional samples). Bacterial and fungal communities were analyzed by high-throughput sequencing of 16S rDNA (V3-V4) and internal transcribed spacer (ITS) regions, respectively. An antifungal L. plantarum YM-4-3 strain was isolated, and its cell-free supernatant was assessed for antifungal activity, stability, and minimum inhibitory concentrations against Trichophyton rubrum and C. albicans. Scanning electron microscopy, transmission electron microscopy, and quantitative PCR were employed to investigate ultrastructural damage and bacteriocin-related gene expression. RESULTS: At the phylum level, Proteobacteria (64.6%), Actinobacteria (18.4%), and Firmicutes (15.2%) dominated bacterial communities, whereas Basidiomycota (57.4%) and Ascomycota (42.3%) accounted for 99.7% of fungal reads. Genus-level profiling revealed that Pseudomonas, Corynebacterium, and Staphylococcus were abundant at both sites, yet Lactobacillus was significantly enriched adjacent to lesions (2.6% vs. 0.6%). Among fungi, Cryptococcus and Trichophyton prevailed, with C. albicans more abundant in lesions. The L. plantarum YM-4-3 cell-free supernatant exhibited the strongest inhibition against C. albicans when grown in MRS with 2.0% NaCl, reaching pH 4.06 after 12 h co-culture. SEM showed the supernatant disrupted the cell wall and membrane of T. rubrum. qPCR indicated a 7.5-fold up-regulation of the bacteriocin gene plnJK under 2.0% NaCl. Ketoconazole (MIC < 1 μg/mL) and terbinafine (MIC 1-2 μg/mL) were highly active against T. rubrum, while amphotericin B (MIC < 1 μg/mL) was most effective against C. albicans. Although the concentrated L. plantarum YM-4-3 supernatant had higher MICs (64-128 mg/mL), inhibition rates exceeded 87%, declining with increased salinity. CONCLUSIONS: These findings reveal distinct microbial signatures associated with tinea corporis and demonstrate the salt-dependent antifungal potential of L. plantarum YM-4-3. This study provides a theoretical basis for novel antifungal probiotic formulations and offers a new strategy to circumvent adverse effects and resistance associated with conventional antifungal therapies.