Antifungal drug resistance in oral Candida isolates from HIV-infected and healthy individuals and efficacy of chitosan as an alternative antifungal agent.

OBJECTIVE:This study aimed to investigate antifungal resistance in oral Candida isolates and the efficacy of chitosan, a natural polymer, against drug-resistant Candida. DESIGN:Oral Candida isolates were collected from HIV-infected and healthy individuals in our previous study (n = 66 isolates/group). The minimum-inhibitory-concentration (MIC) of amphotericin-B and fluconazole was determined by Epsilometer test. Minimal-fungicidal-concentration (MFC) of 3 chitosan derivatives: high-molecular-weight chitosan (HMWC, 150-200 kDa), oligomer (7-9 kDa) and polymer (900-1000 kDa) chitosan, were investigated by agar dilution method. Statistical analysis was performed using Chi-square or Fisher's exact tests as appropriate. RESULTS:Fluconazole-resistant C. albicans were significantly more prevalent in HIV-infected than in healthy individuals (P = 0.02), while amphotericin-B-resistant C. parapsilosis were more common in healthy individuals (P = 0.03). The majority of Candida isolates were killed by HMWC at ≤ 40 mg/ml, as well as by oligomer and polymer chitosan at ≤ 6 mg/ml. Remarkably, chitosan was effective against most antifungal drug-resistant isolates. CONCLUSIONS:Antifungal drug resistance was prevalent among oral C. albicans isolates from HIV-infected individuals. Chitosan could serve as a complementary antifungal agent against drug-resistant strains.