Candida spp. are a leading cause of bloodstream infection (BSI) and are associated with high mortality rates. Biofilm production is a virulence factor of Candida spp., and has been linked with poor clinical outcome. The aim of our study was to assess biofilm production of Candida bloodstream isolates at our institute, and to determine whether in vitro biofilm production is associated with any clinical characteristics of infection. During the four-year study period, 93 cases of Candida BSI were analysed. The most frequently isolated species was C. albicans (66.7 %), followed by C. glabrata (9.7 %), C. parapsilosis (9.7 %), C. tropicalis (9.7 %) and C. krusei (4.3 %). Biofilm production was more prevalent among non-albicans Candida spp. (77.4 %) than C. albicans (30.6 %) (P50.02). Abdominal surgery was identified as a risk factor of BSI caused by biofilm producing non-albicans Candida isolates. No risk factors predisposing to bloodstream infection caused by a biofilm producing C. albicans isolate were identified. Biofilm production was not verified as a risk factor of mortality.

2 Graphical Abstract 3 Highlights Kosmotropes induce the aggregation and fusion of PEG-liposomes.  The effect depends on both the kosmotrope and PEG concentration.  Aggregation is reversible under certain conditions.  Kosmotropes lead to a dehydration-related conformational change of the PEG polymer.  The likely driving force behind aggregation is the hydrophobic effect. 4 ABSTRACTPolyethylene glycol (PEG) is widely used to sterically stabilize liposomes and improve the pharmacokinetic profile of drugs, peptides and nanoparticles. Here we report that ammonium sulfate (AS) can evoke the aggregation of PEGylated vesicles in a concentration-dependent manner. Liposomes with 5 mol% PEG were colloidally stable at AS concentrations up to 0.7 mM, above which they precipitated and formed micron-size aggregates with irregular shape. While aggregation was reversible up to 0.9 M of AS, above 1 M fusion occurred, which irreversibly distorted the size distribution. Zeta potential of liposomes markedly increased from -71±2.5 mV to 2±0.5 mV upon raising the AS concentration from 0 to 0.1 M, but no considerable increase was seen during further AS addition, showing that the aggregation is independent of surface charge. There was no aggregation in the absence of the PEG chains, and increasing PEG molar % shifted the aggregation threshold to lower AS concentrations. Changes in the FTIR spectral features of PEGylated vesicles suggest that AS dehydrates PEG chains. Other kosmotropic salts also led to aggregation, while chaotropic salts did not, which indicates a general kosmotropic phenomenon. The driving force behind aggregation is likely to be the hydrophobic effect due to salting out the polymer similarly to what happens during protein purification or Hydrophobic Interaction Chromatography. Since liposome aggregation and fusion may result in difficulties during formulation and adverse reaction upon application, the phenomena detailed in this paper may have both technological and therapeutical consequences.