Terapia fotodinâmica contra infecção sistêmica por Candida albicans: eficácia em Galleria mellonella

Abstract

Candida albicans is involved in the emergence of antifungal resistance and presents numerous virulence factors, the main one being the ability to form biofilms. Biofilms are highly tolerant to the action of antifungal drugs, with C. albicans biofilm infections being more difficult to treat. PDT is a promising antimicrobial therapy and may be an important adjunct in antifungal treatment. The objective of this work was to evaluate the effectiveness of PDT in the treatment of infections of planktonic cells and biofilms of C. albicans in the in vivo model of G. mellonella. The inoculum of C. albicans, strains ATCC 90028 and clinical isolate A2 were prepared at a concentration of 2x108, a lethal concentration. Clinical isolate A2 was isolated under ethics committee approval, number: 51779315.7.0000.5187. Larvae were inoculated with planktonic forms and 48-hour biofilms. G. mellonella larvae were infected and treated with Fluconazole, Photobiomodulation and PDT. The laser energy used corresponded to a dose of 15 J/cm2 with a wavelength of 650 nm and power of 100 mW continuously, for 2 minutes and 30 seconds. The larvae were observed after the first 4 hours and then at intervals of 24 hours, for 120 hours. After the survival curve, the hemolymph of the larvae was collected and plated. The plates were incubated for 48 hours and the amount of CFU formed was counted. Significant results were observed for PDT and treatment with fluconazole in survival and reduction of fungal burden. PDT showed positive action against C. albicans, including against biofilms. Treatment with red laser light alone did not impact greater survival of the larvae and also did not present positive results in reducing C. albicans infection in G. mellonella.