Evaluation of triazole-echinocandin interactions against Candida parapsilosis planktonic cells and biofilms
Abstract number: P1814
Chatzimoschou A., Simitsopoulou M., Antachopoulos C., Walsh T.J., Roilides E.
Objectives:Candida parapsilosis (CP) frequently causes nosocomial blood stream infections, especially in neonates and patients with central venous catheters. Antifungal triazoles are commonly used in combination with echinocandins in cases of serious fungal infections. While triazoles have been previously shown to have antifungal activity against Candida biofilms (BF) only at very high concentrations (>256 mg/L, Katragkou et al, AAC 2008; 52: 357), little is known about the combined activity of these antifungal drug classes against CP BF. Therefore, we investigated the activities of two triazoles, voriconazole (VRC) and posaconazole (PSC), against CP BF or planktonic cells (PL) in combination with each of two echinocandins, caspofungin (CAS) and anidulafungin (AND).
Methods: CP-A71, a well documented BF-producing CP strain, was grown in RPMI at 5×105 blastoconidia/mL on silicone disks in 96-well plates at 37°C for 48 h in order to produce BFs. PL of CP were grown in yeast nitrogen base growth media at 37°C for 24 h. PL and BFs were then incubated for an additional 24 h with 2-fold dilutions of VRC or PSC (161024 mg/L) and CAS or AND (016 mg/L), alone or concurrently, PSC/VRC with AND/CAS in a checkerboard format. The degree of fungal damage induced on BF and PL was assessed by the XTT metabolic assay. The interactions between VRC+CAS, VRC+AND, PSC+CAS and PSC+AND were analyzed using the Bliss model (Meletiadis et al, Med. Mycol. 2005; 43: 133). Synergy, antagonism or indifference was concluded when the observed BF damage was significantly higher than, lower than or equal to the expected theoretical damage, respectively.
Results: The interaction between VRC at concentrations from 32 to 1024 mg/L and CAS at concentrations from 1 to 16 mg/L was antagonistic against CP PL but indifferent against CP BF. The other drug combinations (VRC+AND, PSC+CAS, PSC+AND) were indifferent against CP PL or BFs.
Conclusions: The antagonistic or indifferent interactions between triazoles and echinocandins, observed against C. parapsilosis PL or BFs at the concentrations studied, do not support the concurrent administration of these antifungal classes in cases of C. parapsilosis infections of vascular catheters.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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