Background Biofilm formation is an important component of vascular catheter infections caused by Candida albicans. Little is known about the interactions between human phagocytes and antifungal agents on Candida biofilms. Materials and Methods The interactions of C. albicans biofilms with human phagocytes alone and in combination with anidulafungin or voriconazole were investigated and compared with their corresponding planktonic counterparts using an in vitro biofilm model with clinical intravascular and green fluorescent protein (GFP) expressing strains. Phagocyte- and antifungal agent-mediated damages were determined by 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]2H-tetrazolium-5-carboxanilide assay and structural effects visualized by confocal microscopy. Oxidative burst was evaluated by flow cytometric measurement of dihydrorhodamine (DHR)-123 oxidation and cytokine release measured by EIA. Results Phagocytes alone or in combination with antifungal agents induced less damage against biofilms as compared to planktonic cells. However, additive effects occurred between phagocytes and anidulafungin against Candida biofilms. Confocal microscopy demonstrated absence of phagocytosis within biofilms, but marked destruction caused by anidulafungin and phagocytes. Anidulafungin but not voriconazole elicited a TNF-α release from phagocytes compared with untreated biofilms. Conclusions Candida albicans within biofilms are more resistant to phagocytic host defenses but are susceptible to additive effects between phagocytes and an echinocandin.

The activities of voriconazole, posaconazole, caspofungin, and anidulafungin against Candida albicans and Candida parapsilosis biofilms were evaluated. In contrast to planktonic cells, the MICs for voriconazole and posaconazole for the biofilms of the two species were high (>256 and >64 mg/liter, respectively) but relatively low for the echinocandins caspofungin and anidulafungin (<1 and <2 mg/liter, respectively).Candida spp. have frequently been associated with the formation of biofilms on biological and inert surfaces, such as intravascular catheters (15). Candida albicans and Candida parapsilosis are the most prevalent species related to the biofilm mode of growth (12). Resistance of Candida biofilms to conventional antifungal agents has been previously documented (2, 10, 16). Given that biofilm-associated infections are very difficult to cure without device removal, the demand for newer, more effective therapies has been developed.The goal of the present study was to examine the activities of newer antifungal agents against C. albicans and C. parapsilosis biofilms and compare them to their corresponding planktonic cells. Voriconazole (VRC; Pfizer, Groton, CT), posaconazole (PSC; Schering-Plough, Kenilworth, NJ), caspofungin (CAS; Merck, Whitehouse Station, NJ), and anidulafungin (AND; Pfizer), were examined.Documented biofilm-producing strains were used, including C. albicans M61, C. albicans GDH2346, and C. parapsilosis PA/71 (4, 5). Aliquots were maintained in 25% glycerol and 75% peptone at Ϫ35°C.Planktonic MICs were determined according to the Clinical and Laboratory Standards Institute M27-A2 method. MICs were determined as the lowest drug concentrations at which a prominent decrease in turbidity was observed, corresponding to ca. 50% inhibition in growth (8-10, 13). The MICs were recorded after incubation for 24 h.Biofilm MIC determination was based on modifications of methods previously described (5, 10, 16). Biofilms were grown on the surface of silicone elastomer disks (Bioplexus Corp., Saticoy, CA), pretreated with fetal bovine serum (Gibco, Paisley, Scotland), in 12-or 96-well plates for 48 h for C. albicans strains and 72 h for C. parapsilosis. In an effort to make our adopted model resemble in vivo conditions, organisms were grown on the surface of a silicone substrate coated with a fetal bovine serum-conditioning film under constant linear shaking (4). Mature biofilms were then incubated in RPMI 1640 containing VRC, PSC, CAS, or AND at doubling dilutions ( Fig. 1 and 2) for 24 h. Drugfree biofilms containing only RPMI 1640 served as controls. Four replicate biofilms were used for each condition. Biofilm MICs were determined as the minimum antifungal drug concentrations that caused Ն50% reduction in the metabolic activity of the biofilms compared to controls (10). Biofilm formation and antifungal activities were assessed by 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]2H-tetrazolium-5-carboxanilide (XTT; 0.25 mg/ml) and coenzyme Q (40 g/ ml) assay spectrophotometrically at 450 nm with a reference wa...

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Biofilm formation complicates the treatment of various infections caused by

Besides a lack of antagonistic interactions between newer antifungal agents and phagocytes, anidulafungin exerts additive immunopharmacological activity against C. parapsilosis biofilms.