Candida Biofilm Characteristics on Central Venous Catheters Associated with Serum

Objectives:  Candida species are a leading cause of intravascular infections in immuno-compromised individuals. To  characterize the biofilm  development of five Candida species on central venous catheter (CVC) surfaces in YNB / human serum medium,  b) to determine the variations of mRNA expression of biofilm specific hydrolytic enzymes of C. albicans SC5314  and,  c) to evaluate the antimycotic efficacy of amphotericin B,  fluconazole, 5-FC individually or in combination against eradicating C. albicans biofilms.  Methods: Biofilm growth of Candida species on CVCs was monitored in YNB with/ without 3% human serum using the tetrazolium reduction assay and further characterized using scanning electron microscopy (SEM). The differential mRNA transcript levels of biofilm associated genes were determined by quantitative real-time PCR analysis.  Chekerboard methodology was used to assess biofilm susceptibility to antimycotics.  Results: 1) Significant intra- and inter- species biofilm growth was observed for all five Candida species on human serum coated CVC coupons  (p<0.001),  which was confirmed by SEM.   2) Significant variations in mRNA transcripts of hydrolytic enzyme genes, SAP1-SAP10,  PLB1, PLB2, PLC and PLD were observed for C. albicans (for at least one time point) grown on CVCs in the presence of serum and compared with serum-free controls,  3) Antifungal susceptibility tests demonstrated that  combinations of amphotericin B paired with either  fluoconazole or 5-flucytosine demonstrated indifferent interactions against C. albicans biofilms as compared to a single antifungal. Conclusions: Human serum enhances biofilm growth of Candida  on CVCs and upregulates mRNA transcripts of a number of extracellular hydrolytic enzymes, and promotes increased resistance to antifungals.