Effects of antifungals and histatin 5 on Candida albicans biofilms

ORCiD

Nejat Düzgüneş: 0000-0001-6159-1391

Department

Biomedical Sciences

Document Type

Conference Presentation

Conference Title

87th General Session of the International Association for Dental Research (IADR) and 38th Annual Meeting of the American Association for Dental Research (AADR)

Location

Miami, FL

Conference Dates

April 1-4, 2009

Date of Presentation

4-4-2009

Journal Title

Journal of Dental Research

Journal ISSN

0022-0345

Journal Volume Number

88 (Special issue A)

First Page

3114

Abstract

Objectives: Candida biofilms are more resistant to antimicrobials than planktonic cells, which may explain the high recurrence of candidal denture stomatitis. Salivary histatins, especially histatin 5 (Hst5), possess significant antifungal properties. We examined the susceptibility of C. albicans biofilms on denture acrylic to Hst5 and the antifungals, amphotericin B, nystatin, and fluconazole. Methods: Biofilms were developed on poly(methyl methacrylate) discs submerged in C. albicans cell suspensions. The plate was incubated for 90 min at 37°C (adherence phase). After removal of non-adherent cells, discs were submerged in YNB/100 mM glucose medium and incubated for 48 h at 37°C (biofilm formation phase). The antifungals were present either during biofilm formation, or added after biofilm formation. The metabolic activity of Candida biofilms was measured by the XTT assay. Results: Fluconazole showed the greatest inhibitory effect, when present during biofilm formation, reducing metabolic activity by ~30% at 0.25 µg/ml, while amphotericin B and nystatin were not inhibitory at this concentration. All three drugs were equally inhibitory (>90%) at 2 µg/ml. Biofilm-associated Candida was highly resistant to fluconazole in the range 1-64 µg/ml. Nystatin and amphotericin B were more inhibitory. At 1 µg/ml, amphotericin B and nystatin reduced the relative XTT activity by 56 and 85%, respectively. Hst5 inhibited the XTT activity of biofilm Candida by 40% at 50 µM, and 60% at 100 µM. Conclusions: Fluconazole, an inhibitor of ergosterol synthesis, was more effective during biofilm formation, most likely because fungal proliferation is dependent on cell membrane synthesis. In contrast, the polyenes were effective after biofilm formation, because they disrupt already synthesized cell membranes. Hst5 could also affect biofilm Candida by internalization and ATP depletion. Supported by Research Pilot Project Award 03-Activity 054 from the University of the Pacific, Arthur A. Dugoni School of Dentistry (K. Konopka), and by funds from Western Dental Services.

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