Biofilm-forming Capacity of Candida Bloodstream Isolates from Neonatal Intensive Care Units Neonates

Background: The incidence of candidaemia is steadily increasing in n is considered a virulence factor responsible for catheter-related candidaemia. Objective: To investigate the capacity of bloodstream Candida isolates from NICU neonates to form BF and the degree of BF production. Methods: 5x10 5 planktonic (PL) cells/mL were grown in YNB medium with 2% glucose at 37°C for 24h. For BF formation, 10 6 cells/mL were grown on silicone disks placed at the bottom of 96-well plates in RPMI-1640 under constant shaking at 37°C for 48-72 h. BF production was then evaluated by XTT metabolic assay, safranin staining and light microscopy (LM). Documented BF producers (CA-M61 and CP/PA71) were used as positive controls (metabolic activity by XTT assay: 100%). Isolates that a) showed XTT conversion ≥80% of positive controls, b) stained with safranin and c) produced a microscopically visible dense fungal network were considered high BF producers. XTT conversion of <80% defined non-BF producers, while conversion ≥80% with inconsistent safranin and LM findings defined low BF producers. All isolates were tested in triplicate at 3 different experiments. Results: A total of 31 isolates coming from equal in number NICU neonates (12 male-19 female) with Candida bloodstream infections were examined. Among these isolates, 58% were Candida albicans (CA), 19% were Candida parapsilosis (CP), 7% were Candida lusitaniae (CL) and Candida guilliermondii (CG), respectively, 3% were Candida glabrata (CGl), Candida tropicalis (CT) and other Candida spp. (Cs), respectively. BF production was detected in all CG and CT isolates, in 88% of CA, in 50% of CL and in 17% of CP. CGl and Cs isolates did not produce BF. Among CG and CT isolates, all were high BF producers, 56% and 28% CA isolates were high and low BF producers, respectively. Conclusions: BF-forming capacity is a frequent characteristic among Candida clinical isolates, especially for CG, CT, CA but not for CGl. These results may provide the means to design novel therapies for BF-related infections.