In vitro anti-dermatophytic activity of soil streptomyces against dermatophyte isolates

Background Antifungal treatment failure and reduced susceptibility among dermatophytes highlight the need to investigate additional antifungal leads. This study evaluated the preliminary in vitro anti-dermatophytic activity of soil-derived Streptomyces isolates against a set of dermatophyte isolates. Method Soil samples from three non-agricultural sites in Mogadishu were processed for isolation of Streptomyces. Seven isolates were characterized morphologically and biochemically. Antifungal activity was evaluated in triplicate against phenotypically identified Trichophyton spp., Microsporum spp ., and Epidermophyton floccosum using agar-based inhibition assays; MIC and MFC of Streptomyces extracts were determined by broth microdilution and recovery culture. The original records describe itraconazole and normal saline as positive and negative controls, respectively, but the reported itraconazole concentration (100 mg/mL), solvent, final working concentration, mode of control application, and numerical control results could not be verified from the available records. Griseofulvin MIC values, validated interpretive breakpoints, and adequately documented susceptible reference-strain results were also unavailable; therefore, the dermatophytes are not classified as griseofulvin-resistant in this revision. Streptomyces cultures were fermented to obtain crude metabolites; aqueous extracts were used for preliminary antifungal screening, ethyl acetate extracts were profiled by GC-MS, and major tentatively assigned metabolites from the most active isolate were evaluated by molecular docking against fungal lanosterol 14α-demethylase (CYP51) using AutoDock Vina. Result All seven isolates exhibited measurable preliminary in vitro anti-dermatophytic activity, with isolate B-6 showing the strongest overall effect. Against Trichophyton spp., B-6 produced a 27 ± 0.36 mm inhibition zone with MIC 0.0625 mg/mL and MFC 0.125 mg/mL; against Microsporum spp ., the inhibition zone was 25 ± 0.31 mm with MIC 0.125 mg/mL and MFC 0.25 mg/mL; and against E. floccosum, the inhibition zone was 27 ± 0.24 mm with MIC 0.0625 mg/mL and MFC 0.125 mg/mL. GC-MS produced tentative metabolite assignments, including β-carboline, quercetin, and terpineol in B-6; these assignments require orthogonal confirmation. Docking predicted binding energies of −10.0, −8.4, and −6.5 kcal/mol for quercetin, β-carboline, and terpineol, respectively, compared with −10.4 kcal/mol for itraconazole. Conclusion The findings demonstrate preliminary in vitro activity of soil-derived Streptomyces against the specific dermatophyte isolates tested and identify B-6 as the most active isolate under the experimental conditions. These are not clinical efficacy data. Because the Trichophyton and Microsporum isolates were not identified to species or species-complex level, activity was not demonstrated against all species within either genus, and no species-wide therapeutic or efficacy claim is made.