Inhibitory effect of proteinase K against dermatophyte biofilms: an alternative for increasing the antifungal effects of terbinafine and griseofulvin.

This study aimed to evaluate the effect of proteinase K on mature biofilms of dermatophytes, by assays of metabolic activity and biomass. In addition, the proteinase K-terbinafine and proteinase K-griseofulvin interactions against these biofilms were investigated by the checkerboard assay and scanning electron and confocal microscopy. The biofilms exposed to 32 µg ml-1 of proteinase K had lower metabolic activity and biomass, by 39% and 38%, respectively. Drug interactions were synergistic, with proteinase K reducing the minimum inhibitory concentration of antifungals against dermatophyte biofilms at a concentration of 32 µg ml-1 combined with 128-256 µg ml-1 of terbinafine and griseofulvin. Microscopic images showed a reduction in biofilms exposed to proteinase K, proteinase K-terbinafine and proteinase K-griseofulvin combinations. These findings demonstrate that proteinase K has activity against biofilms of dermatophytes, and the interactions of proteinase K with terbinafine and griseofulvin improve the activity of drugs against mature dermatophyte biofilms.

Biofilm formation on cat claws by Sporothrix species: An ex vivo model.

This work aimed to evaluate the ability of Sporothrix species to attach and form biofilm on the surface of cat claws as an ex vivo model. A total of 14 strains (5 Sporothrix brasiliensis, 3 Sporothrix schenckii s. str., 3 Sporothrix globosa and 3 Sporothrix mexicana) were used. The biofilms were incubated for periods of 01, 03, 07, 10 and fifteenth 15 days. Their metabolic activities were evaluated by the XTT reduction assay and the morphology and structure were investigated by scanning electron microscopy (SEM). The analysis of the SEM images revealed that all the species can form biofilms on cat claws. The metabolic activity in the ex vivo biofilms was similar to that found in in vitro biofilms when incubated for the same period. This is the first report of an ex vivo biofilm model involving cat claws. The ability to form biofilms on cat claws can increase the viable period of the fungus and consequently the number of possibly infected animals and people.

Antifungal effects of the flavonoids kaempferol and quercetin: a possible alternative for the control of fungal biofilms.

This study aimed to determine the minimum inhibitory concentration (MIC) of kaempferol and quercetin against planktonic and biofilm forms of the Candida parapsilosis complex. Initially, nine C. parapsilosis sensu stricto, nine C. orthopsilosis and nine C. metapsilosis strains were used. Planktonic susceptibility to kaempferol and quercetin was assessed. Growing and mature biofilms were then exposed to the flavonoids at MIC or 10xMIC, respectively, and theywere also analyzed by confocal laser scanning microscopy. The MIC ranges were 32-128 µg ml-1 for kaempferol and 0.5-16 µg ml-1 for quercetin. Kaempferol and quercetin decreased (P < 0.05) the metabolic activity and biomass of growing biofilms of the C. parapsilosis complex. As for mature biofilms, the metabolic effects of the flavonoids varied, according to the cryptic species, but kaempferol caused an overall reduction in biofilm biomass. Microscopic analyses showed restructuring of biofilms after flavonoid exposure. These results highlight the potential use of these compounds as sustainable resources for the control of fungal biofilms.