Activity of Chitosan Derivatives Against Common Oral Candida Species

Objectives: Several Candida species are commonly found in the oral cavity as normal flora, but could cause infection in denture wearers and in immunocompromised patients. Among these, some species are intrinsically resistant to currently available antifungal drugs. Chitosan is a natural product with antimicrobial activity against many bacteria and fungi. To investigate the potential use of chitosan as an adjunctive or alternative antifungal agent for oral infection, we analyzed the activity of chitosan derivatives against common oral Candida species in vitro.
Methods: Broth dilution assays for 3 derivatives of chitosans: N-succinyl chitosan, and low (45,000 Da) and high (150,000-200,000 Da) molecular-weight (MW) water-soluble chitosans, were carried out against Candida albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei. After 24 hours incubation with serial dilutions of chitosan, the cultures were plated on rich media to determine the Minimal Fungicidal Concentrations (MFC).
Results: The MFC of the high MW water-soluble chitosan ranged from 0.625 to 2.5 mg/ml, and that of N-succinyl chitosan was 1-5 mg/ml. However, low MW chitosan was not effective against any species at the highest concentration tested (15 mg/ml). C. albicans, C. tropicalis, C. parapsilosis, and C. krusei were similarly sensitive to chitosans, whereas C. glabrata was not.
Conclusions: Among the 3 derivatives of chitosan, high MW water-soluble chitosan showed the highest level of antifungal activities against most oral Candida species in this study.