During the last three decades the number of fungal infections caused by yeasts of Candida spp. has increased dramatically, mainly due to the rise in the number of immunocompromised patients. Moreover,the increasing number of clinical isolates resistant to current antifungal therapies highlight the need for search for new therapeutic alternatives. Many studies have been conducted on the antifungal activity of natural products (include essential oils) against Candida spp. involved in fungal infections. Tea tree oil (TTO) is an essential oil that is obtained by steam distillation of the leaves and terminal branches of Melaleuca alternifolia (Myrtaceae). TTO is used as a local agent for treating various diseases, predominantly dermatoses (e.g., recurrent herpes labialis, acne,pustules,dandruff, and rash). It has a broad spectrum of antimicrobial activity against a wide range of bacteria, viruses, and fungi, as well as microorganisms that are resistant to conventional drugs. However, clinical experience showed that the efficacy of antimicrobial drugs depends both on their direct effect on microorganisms and the activity of the host immune system. Hence, the purpose of this study was to evaluate the influence of TTO, at subinhibitory concentrations,on intracellular killing by human polymorphonuclear leukocytes (PMNs) against Candida krusei, in comparison with anidulafungin (AND),one of the common antifungal drugs used in candidiasis management. A clinical C. krusei strain was used.The EO was purchased from Primavera/Flora,Pisa,Italy, and analysed by GC (Drug Science and Technology Dept).AND (Pfizer)was provided by Prof. Milici (University of Palermo). Susceptibility testing was based on the CLSI M27-A3 method, with some modifications. Intracellular killing was investigated by incubating yeasts (106cfu/mL) and PMNs (106cells/mL) at 37°C for 30, 60,90 min in presence of TTO subinhibitory concentrations and 1/2MIC of AND. Killing values were expressed as Survival Index. EO/AND-free controls were included. Statistical evaluation of the differences between test and control results was performed by Tukey’s test. The cytotoxicity of various concentrations of TTO was evaluated with MTT test assay. Results showed that TTO at higher concentrations(i.e.1/4MIC)was toxic, as it could interfere with the PMN functionality. On the contrary, TTO at 1/8 MIC significantly enhanced intracellular killing of C. krusei by PMNs, with killing values higher in comparison with those observed in free-EO systems and in presence of AND, indicating that the decreasing concentrations did not cause lower candidacidal activity. These data show a promising potential application of TTO against C. krusei, often resistant to conventional drugs.
File in questo prodotto:
Non ci sono file associati a questo prodotto.