Biofilm formation in S. aureus isolates of bloodstream infections and commensal origin. Biofilm formation between S. aureus isolates of the same clonal lineage from blood stream infections (CC8 n = 15, CC7 n = 11) and of commensal origin (CC8 n = 15, CC7 n = 15), no significant differences were found (a). S in the legend represents MSSA, BSI represents bloodstream isolates and C represents commensal isolates. Number on each bar refers to number of isolates. Absorbance (A590) of the crystal violet stained biofilm matrix of strong biofilm formers at different glucose concentrations (b). CRA screening for colonies with a dry crystalline morphology (c).