Synergistic effect of amphotericin B and tyrosol on biofilm formed by Candida krusei and Candida tropicalis from intrauterine device users

The presence of intrauterine contraceptive devices (IUDs) provides a solid surface for attachment of microorganisms and an ideal niche for the biofilm to form and flourish. Vaginal candidiasis is often associated with the use of IUDs. Treatment of vaginal candidiasis that develops in connection with IUD use requires their immediate removal. Here, we present in vitro evidence to support the use of combination therapy to inhibit Candida biofilm. Twenty-three clinical Candida isolates (10 C. krusei and 13 C. tropicalis) recovered from endocervical swabs obtained from IUD and non-IUD users were assessed for biofilm-formation ability. The rate of isolation of Candida did not differ significantly among IUD and non-IUD users (P = 0.183), but the biofilm-formation ability of isolates differed significantly (P = 0.02). An in vitro biofilm model with the obtained isolates was subjected to treatment with amphotericin B, tyrosol, and a combination of amphotericin B and tyrosol. Inhibition of biofilm by amphotericin B or tyrosol was found to be concentration dependent, with 50% reduction (P < 0.05) at 4mg/l and 80μM, respectively. Hence, a combination effect of tyrosol and amphotericin B was studied. Interestingly, approximately 90% reduction in biofilm was observed with use of 80μM tyrosol combined with 4mg/l amphotericin B (P < 0.001). This represents a first step in establishing an appropriate antibiofilm therapy when yeasts are present.