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Thirty clinical isolates of Candida albicans were collected from blood or other sterile site infections. Biofilm dry weight and metabolic activity were measured for each isolate. Planktonic and sessile antifungal susceptibilities of each isolate were determined for amphotericin B deoxycholate, caspofungin, and voriconazole. Sessile susceptibilities were determined for the combination of caspofungin/voriconazole. No significant differences in biofilm dry weight or metabolic activity were found between bloodstream and other invasive isolates. Planktonic MIC90 values and sessile MIC90 (SMIC90) values were 0.25 and 2, 0.06 and >256, and 0.5 and 2 microg/mL for amphotericin, voriconazole, and caspofungin, respectively. The SMIC90 of the combination of caspofungin/voriconazole against sessile isolates was 0.5/2 microg/mL. Therefore, the source of invasive C. albicans clinical isolates did not affect in vitro biofilm formation. Susceptibility to antifungal agents decreased when C. albicans was associated with biofilm, and the combination of caspofungin/voriconazole did not appear to provide enhanced activity compared with caspofungin alone.

Candida albicans biofilms complicate the treatment of infected implanted intravascular devices because of decreased antifungal susceptibility. In our investigation, 48 rabbits with experimental central venous catheter C. albicans infection were equally allocated to a control arm or to receive amphotericin B deoxycholate or caspofungin treatment while undergoing systemic and intraluminal lock therapy for 7 days. C. albicans was cultured from catheters from all control rabbits, from 3 that received amphotericin B, and from 0 that received caspofungin. Differences in colony counts were detected between the control and amphotericin (P<.001) and control and caspofungin (P<.001) arms. Caspofungin may be useful in the treatment of C. albicans biofilm-associated intravascular catheter infections, which warrants further study.