[Activity of amphotericin B and anidulafungin, alone and combined, against Candida tropicalis biofilms developed on Teflon® and titanium]

Abstract

Background: Current therapeutic strategies have a limited efficacy against Candida biofilms that form on the surfaces of biomedical devices. Few studies have evaluated the activity of antifungal agents against Candida tropicalis biofilms.

Objectives: To evaluate the activity of amphotericin B (AMB) and anidulafungin (AND), alone and in combination, against C. tropicalis biofilms developed on polytetrafluoroethylene (teflon -PTFE) and titanium surfaces using time-kill assays.

Methods: Assays were performed using the CDC Biofilm Reactor equipped with PTFE and titanium disks with C. tropicalis biofilms after 24h of maturation. The concentrations assayed were 40mg/l for AMB and 8mg/l for AND, both alone and combined. After 24, 48 and 72h of exposure to the antifungals, the cfu/cm² was determined by a vortexing-sonication procedure.

Results: AMB reduced biofilm viable cells attached to PTFE and titanium by ≥99% and AND by 89.3% on PTFE and 96.8% on titanium. The AMB+AND combination was less active than AMB alone, both on PTFE (decrease of cfu/cm² 3.09 Log₁₀vs. 1.08 when combined) and titanium (4.51 vs. 1.53 when combined), being the interaction irrelevant on both surfaces.

Conclusions: AMB is more active than AND against C. tropicalis biofilms. Yeast killing rates are higher on titanium than on PTFE surfaces. The combination of AMB plus AND is less effective than AMB alone on both surfaces.

Keywords: Amphotericin B; Anfotericina B; Anidulafungin; Anidulafungina; Biofilm; Biopelícula; Candida tropicalis; Politetrafluoroetileno; Polytetrafluoroethylene; Titanio; Titanium.