Antifungal activity against planktonic and biofilm Candida albicans in an experimental model of foreign-body infection

Objectives: The treatment of Candida implant-associated infections remains challenging. We investigated the antifungal activity against planktonic and biofilm Candida albicans in a foreign-body infection model. Methods: Teflon cages were subcutaneously implanted in guinea pigs, infected with C. albicans (ATCC 90028). Animals were treated intraperitoneally 12 h after infection for 4 days once daily with saline, fluconazole (16 mg/kg), amphotericin B (2.5 mg/kg), caspofungin (2.5 mg/kg) or anidulafungin (20 mg/kg). Planktonic Candida was quantified, the clearance rate and cure rate determined. Results: In untreated animals, planktonic Candida was cleared from cage fluid in 25% (infected with 4.5 × 103 CFU/cage), 8% (infected with 4.8 × 104 CFU/cage) and 0% (infected with 6.2 × 105 CFU/cage). Candida biofilm persisted on all explanted cages. Compared to untreated controls, caspofungin reduced the number of planktonic C. albicans to 0.22 and 0.0 CFU/ml, respectively, and anidulafungin to 0.11 and 0.13 CFU/ml, respectively. Fluconazole cured 2/12 cages (17%), amphotericin B and anidulafungin 1/12 cages (8%) and caspofungin 3/12 cages (25%). Conclusion: Echinocandins showed superior activity against planktonic C. albicans. Caspofungin showed the highest cure rate of C. albicans biofilm. However, no antifungal exceeded 25% cure rate, demonstrating the difficulty of eradicating Candida biofilms from implants.