Antibiotic production by dermatophyte fungi

Thirty-two clinical isolates of anthropophlic dermatophytes were examined for their capacity to produce antibiotics in liquid culture and on human stratum corneum in vitro. Antibiotics were detected and classified using agar diffusion bioassays and chromatographic analysis. Twenty-four isolates produced antibiotic substances in liquid culture filtrates; some strains produced more than one antibiotic. Only four isolates produced detectable levels of antibiotics when grown on stratum corneum unless an artificial sweat mixture was used as a nutrient supplement, when the number rose 11. Respresentatives of all species studied produced benzyl penicillin-like substances. Some Trichophyton isolates also produced streptomycin-like antibiotics, a characteristic previously unrecorded for eukaryotic organisms. Other antibiotics, which apart from azalomycin F could not be properly classified, were produced by Epidermophyton floccosum. Antibiotic production occurred over the normal skin temperature range but sometimes the type of antibiotic produced and the frequency of detection appeared to be influenced by the incubation temperature.