The Synergistic Activity of Eugenol and Fluconazole on the Induction of Necrosis and Apoptosis in Candida Krusei Isolates of HIV+ Patients With Oral Candidiasis

The oral cavity contains more than 200 microbial species. Candida species are also part of the fungal flora of the oral cavity. In recent years, Candida krusei, as a common oral candida in AIDS patients, has been shown resistant to some antifungal drugs. The emergence of multidrug-resistant fungi, especially in immunodeficient populations, is a major global problem. Today, medicinal plants and their pure compounds in treating infectious diseases have provided a new horizon. This study aimed to investigate the synergistic activity of eugenol and fluconazole on the necrosis and apoptosis of Candida krusei (C. krusei) isolates from HIV+ patients with oral candidiasis.

The antifungal susceptibility tests were performed using the broth microdilution (CLSI, M27-A2) method, and the synergy between eugenol and fluconazole was evaluated using the checkerboard method. Necrotic and apoptotic effects of different antifungal agents against C. krusei were analyzed using the flow cytometry method.

In antifungal susceptibility tests by microdilution broth, the mean minimum inhibitory concentration (MIC) values of eugenol and fluconazole for C. krusei isolates were 755.06 and 60.1 µg/mL, respectively. According to the checkerboard test results, eugenol in combination with fluconazole exhibited significant synergistic effects against most of the yeast isolates tested (P<0.05). Eugenol decreased approximately 81.81% of the MIC value of fluconazole in growth inhibition of C. krusei. The flow cytometry test results indicated that eugenol plus fluconazole has significant necrotic effects on C. krusei isolates compared with the control group (P<0.05). In contrast, minor early and late apoptotic effects of this compound were observed. 

Eugenol can be used to reduce fluconazole dose, inhibit the growth of fluconazole-resistant C. krusei, and the necrosis of yeast cells.