Antifungal activity of actinobacteria against fungus isolates of clinical importance

Résumé

The escalating use of antifungal agents and long-term treatment approaches has led to an increased prevalence of fungus species that are resistant to the most common antifungal drugs. Actinobacteria produce a wide variety of bioactive secondary metabolites. This study investigated actinomycete isolates with the potential to produce bioactive compounds against dermatophyte fungus species and Candida spp. of clinical importance. Antifungal activity of actinomycetes was assessed using the double-layer agar technique. Active isolates were cultivated in starch casein broth (SCB) at 30 ºC for 8 days. Aliquots were retrieved at 24-h intervals and centrifuged to obtain extracts. Extract activity was assessed using the well-diffusion method. No dermatophyte fungus isolate was inhibited in the double-layer assay, although isolates 1S, R18(6) and 6(2) were active against all Candida spp. used in the assay. The well-diffusion method revealed that isolate R18(6) inhibited the six Candida spp. in a 72-h growth period in SCB broth, showing good potential to yield a compound with antifungal activity.