Biofilm formation complicates the treatment of various infections caused by species. with AND (0.03 to 0.5 mg/liter) and VRC (32 to 512 mg/liter) with AND (0.008 to 0.03 mg/liter) were antagonistic. Against planktonic cells, the conversation between VRC (32 to 1 1,024 mg/liter) and CAS (1 to 16 mg/liter) was antagonistic. All simultaneous antifungal combinations demonstrated indifferent interactions against biofilms of both species. Damage to biofilms of both species increased (< 0.01) in the presence of subinhibitory concentrations of echinocandins (0.008 to 0.064 mg/liter), followed by the addition of PSC (512 mg/liter for and 64 to 512 mg/liter for and 512 mg/liter for sp. biofilms, while various significant interactions occur with their planktonic counterparts. INTRODUCTION bloodstream infections cause significant morbidity and mortality in critically ill patients (30). and are the species most frequently implicated in vascular-catheter-related candidemia (19, 32, 36). The development of candidemia has been associated with the use of central venous catheters or other implantable prosthetic devices, which are highly susceptible to colonization and infection by yeast cells (7, 17). Guidelines recently published by the Infectious Diseases Society of America (IDSA) (28) recommend prompt removal of the foreign body; however, since antifungal agents, on many occasions, are insufficient to cure biofilm-related infections and catheter removal is not always feasible (24), other approaches, such as combination therapy or lock therapy, have been suggested (25, 29, 33). Biofilm formation is an important virulence factor of spp. in such infections. Yeast cells embedded in biofilms demonstrate phenotypic traits distinct from those of their planktonic counterparts (8, 22, 30). In particular, biofilms exhibit reduced susceptibility to common antimicrobial agents and host defense mechanisms and have survival advantages over planktonic cells (14, 15). Triazoles and echinocandins, two classes of antifungal agents with distinct mechanisms of action (5), are used as standard therapy for infections, according to IDSA guidelines (10, 28). In refractory cases of invasive fungal infections, combinations of triazoles and echinocandins have been studied as promising therapies to reduce high attributable mortality rates (18). Little is known, however, about the combined effects of the newer antifungal triazoles and echinocandins against biofilms of and (1, 31). In the present study, we investigated the combined effects of voriconazole (VRC) or posaconazole (PSC) with anidulafungin (AND) or caspofungin (CAS) against and biofilms or planktonic cells. We studied triazole-echinocandin interactions in two models of simultaneous and sequential treatment. (This study was presented in part at the 48th Annual Meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) and the 46th Annual Meeting of the Infectious Diseases Society of America (IDSA), Washington, DC, 25 to 28 October 2008; the 19th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), Helsinki, Finland, 16 to 19 May 2009; and the 4th Trends in Medical Mycology (TIMM), Athens, Greece, 18 to 21 October 2009.) MATERIALS AND METHODS Strains. Two well-characterized biofilm-producing strains were used. strain M-61 was obtained from an infected intravascular catheter, and strain P/A71 was isolated from sputum. The two strains were kindly donated by M. A. Ghannoum (University Hospital 68573-24-0 manufacture of Cleveland and Case Western Reserve University, Cleveland, OH). Stock cultures were divided into small portions and stored at ?35C in 25% glycerol and 75% peptone. Growth medium and conditions. All strains were grown in yeast nitrogen base (YNB) medium (Difco Laboratories, Detroit, MI) supplemented with 50 mM glucose. Twenty milliliters of YNB medium was inoculated with a loopful of from a freshly inoculated Sabouraud glucose agar plate and incubated on a rocker at 37C overnight. Cells were harvested and washed twice with 0.15 M phosphate-buffered saline (PBS) solution (pH 7.2; Ca2+ and Mg2+ free; Biochrom KG, Berlin, Germany). Yeast cells were resuspended in 10 68573-24-0 manufacture ml of PBS, counted after serial dilutions using 68573-24-0 manufacture a hemocytometer, standardized at 5 105 blastoconidia/ml, and used immediately. Biofilm formation. Biofilms were formed on preconditioned sterile silicone elastomer discs (Bioplexus Corp., Ventura, CA) that had been preincubated with fetal bovine serum (FBS) in 96-well plates (Corning Inc., New York, NY) under constant linear shaking for 24 h. The discs were then washed with PBS to remove residual FBS. For mature-biofilm formation, 5 105 blastoconidia/ml of M-61 or PA/71 were added to the above-mentioned 96-well plates and incubated at 37C under constant shaking in RPMI 1640 (Sigma-Aldrich, St. Louis, MO) for 48 h or 72 h, respectively. After biofilm formation, the 96-well plates were centrifuged at 2,230 for 30 min. The medium was then aspirated, and nonadhering cells were removed by washing them once with sterile PBS (19). Antifungal agents. VRC and AND were provided by Pfizer Inc. (New York, NY), PSC by Schering-Plough (Brussels, Belgium), and CAS by Merck and Co. Inc. (Whitehouse Station, NJ). VRC and FCGR2A CAS were obtained in powder form and.