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Implication of Candida biofilm maturation on the susceptibility to amphotericin B, caspofungin and posaconazole, alone or in combination

Abstract number: P699

Tobudic S., Kratzer C., Graninger W., Lassnigg A., Vorderwinkler A., Fischer H., Presterl E.

Objectives:Candida biofilm-associated infections are a particular challenge in modern implant surgery because of their resistance to conventional therapy. In this work was determined the activity of amphotericin B, caspofungin and posaconazole alone or in combination on biofilms of various Candida species at distinct levels of maturation.

Material and Methods: Biofilms of 44 isolates from blood, central venous catheter, urine, skin swabs and medical devices swabs of cardiac surgery patients (C. albicans n= 25; C. glabrata n = 8, C. parapsilosis n = 5, C. tropicalis n = 2, C. krusei=1, C. famata n = 1, C. norwegiensis n = 1, C. guilliermondi n = 1) were grown for either 24, 48 or 72 hours in 96-well microtiter plates. The biofilms were treated for 48 hours with amphotericin B (AMB), caspofungin (CAS) and posaconazole (POS) alone in increasing concentrations according to the respective MIC (1–128×MIC) and with combination therapy: AMB 0.5 mg/l/CAS 0.5 mg/l or 1 mg/l, and AMB 0.5 mg/l/POS 0.5 mg/l or 1 mg/l. The optical density (OD) was determined using XTT-reduction assay at a wavelength of 450 nm. The OD of the untreated biofilm of the respective isolate was set as 1. To test for viable Candida spp. in the biofilms, the unfixed biofilms were scraped off and seeded to Sabouraud agar.

Results: Treatment with CAS reduced significantly the OD of 24- and 72 hours C. albicans biofilms at concentrations of 1×MIC (p < 0.05), while no significant reduction of the OD of 48 hours old non-albicans Candida biofilm was detected up to a concentration of 128×MIC. AMB reduced the OD of 24- and 72 hours biofilm significantly at concentration of 1×MIC – 4×MIC (p < 0.05). Significant OD reduction of 48 hours old biofilm achieved AMB at concentrations of 8×MIC (C. albicans) and 32×MIC (non-albicans). POS was equally effective at all stages of Candida biofilms and reduced the OD at a concentration of 1×MIC-2×MIC (p < 0.05). Combinations of antifungals led to significant reduction of the OD of the biofilm in the each stage of development (p < 0.01).

Conclusion:Candida biofilms show different degrees of susceptibility to therapy with a single antifungal agent depending of the phase of development. Particularly 48 hours old biofilms exhibit less susceptibility. Combination therapy attained high OD reduction and may be an option for the treatment of biofilm-associated infections.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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