The Inhibitory Effect of Human Beta-defensin-3 on <i>Candida Glabrata</i> Isolated from Patients with Candidiasis

Abstract

<i>Candida glabrata</i> is a common non-<i>albicans Candida</i> species found in patients with candidiasis and it sometimes develops antifungal resistance. Human beta-defensin-3 (hBD-3) is an antimicrobial peptide of immune system active against various types of microbes including <i>Candida spp</i>. This study investigated antifungal activity of hBD-3 and its synergistic effect with a first-line antifungal agent on <i>C. glabrata</i> clinical isolates. <i>Candida spp</i>. were characterised in patients with candidiasis. The antifungal activities of hBD-3 and fluconazole against <i>C. glabrata</i> were evaluated using Broth microdilution assay. The synergistic activity of these two agents was determined by checkerboard microdilution and time-killing assays. The cytotoxicity of hBD-3 was evaluated using LDH-cytotoxicity colorimetric assay. Of 307 episodes from 254 patients diagnosed with candidiasis, <i>C. glabrata</i> was found in 21 clinical isolates. Antifungal susceptibility tests of <i>C. glabrata</i> were performed, fluconazole demonstrated an inhibitory effect at concentrations of 0.25-8 μg/ml, but one antifungal resistant strain was identified (>64 μg/ml). hBD-3 showed an inhibitory effect against all selected strains at concentrations of 50-75 μg/ml and exhibited a synergistic effect with fluconazole at the fractional inhibitory concentration index (FICI) of 0.25-0.50. A concentration of 25 μg/ml of hBD-3 alone showed no cytotoxicity but synergistic activity was seen with fluconazole. In conclusion, hBD-3 has antifungal activity against <i>C. glabrata</i> and synergistic effects with fluconazole at concentrations that alone, have no cytotoxicity. hBD-3 could be used as an adjunctive therapy with first-line antifungal agents for patients with <i>C. glabrata</i> infection particularly those infected with fluconazole-resistant strains.