Efeito do carvacrol sobre fatores de virulência de cepas de Candida albicans isoladas da mucosa oral: um estudo in vitro

Abstract

Oral candidiasis is a fungal infection caused by Candida yeasts, mainly Candida albicans. This infection usually affects the oral mucosa and it is frequently observed in individuals who suffer from immunological impairment. The standard therapeutic approach consists of using conventional antifungal drugs, however, their high levels of toxicity, as well as the emergence of drug resistant strains, request the search for brand new treatment alternatives, in addition to an improved understanding about the impact of such substances on the virulence factors expressed by these pathogens. In this sense, carvacrol, a phenolic monoterpenoid compound, found in oregano essential oils, has stood out for its antifungal and antimicrobial potential. In consideration of that, this investigation aimed to notice the effect of carvacrol on the virulence factors of C. albicans strains isolated from the oral mucosa. The morphogenesis capacity and the lipase activity were the examined virulence aspects. The study involved 13 C. albicans strains collected from the oral mucosa of individuals with oral candidiasis and 1 reference strain (ATCC 90028) which were submitted to every assay under 2 simultaneous conditions: in the presence and in the absence of carvacrol (MIC = 128 μg/mL). The mentioned compound was capable of reducing the germ tube emission in most of the studied strains (from 72,27% ± 14,2% to 13,97% ± 22,2%) and showed efficiency in reducing filamentation (from IM = 2.9 to IM =1,9); as soon as pseudohyphae was the most prevalent morphology in the absence of carvacrol, although, the elongated and spherical cells became most frequent with carvacrol. Afterwards, it was verified that the tested compound could significantly reduce hyphal length on every strain in which remained the hyphal morphology, furthermore it was capable of preventing the formation of filamentous colonies in solid medium, producing uniquely smooth colonies. Finally, carvacrol was efficient inhibiting the lipase activity from each analyzed strain. By highlighting the in vitro influence of carvacrol on the virulence factors of C. albicans, we recommend that this monoterpene should be considered a promising compound added to the formulation of new and efficient antifungal drugs but, obviously, complementary researches aiming its clinical performance are necessary to prove its low toxicity and therapeutic efficacy in human beings.