01) (Figure 3). Of all strains classified as strong biofilm

producers, MRSA and MSSA associated with MLST CC8 produced the most biomass under all tested glucose concentrations (Figure 4a and 4b). Strains defined as strong biofilm formers and associated with MLST CC5, CC25 and CC30 approached approximately the same level of biomass at the following glucose concentrations, Selumetinib i.e. CC5 at 0.25%, CC 25 at 0.5% and CC30 at 0.5% glucose, respectively. Figure 2 Quantification of strong biofilm formation in MSSA and MRSA. Quantification of strains of the specified group defined as strong biofilm former at different glucose concentrations. Black bars represent MRSA, dark grey bars represent MSSA with MRSA associated

MLST CCs and light grey bars represent MSSA with MSSA associated MLST CCs. Asterisks denote statistically significant difference, (*) P < 0.05 and (**) P < 0.01. Figure 3 Biomass quantification of MSSA and MRSA. Absorbance (A 590) of the crystal violet stained biofilm matrix for strong biofilm formers (with A 590 above the threshold value of 0.374, represented by the horizontal dashed line) at different glucose concentrations. Boxplots at the left show MRSA, in the middle MSSA with MRSA associated MLST CCs and PI3K inhibitor at the right MSSA with MSSA associated MLST CCs. The lower and higher boundary of the box indicates the 25th and 75th percentile, respectively. The line within the box marks the median. Whiskers above and below the box indicate the 90th and 10th percentiles. Open circles indicate the 95th and 5th percentiles. Asterisks denote statistically significant difference, (*) P < 0.05 and (**) P < 0.01. Figure 4 Biomass formation related to the genetic background of S. aureus. Absorbance (A 590) of the crystal violet stained biofilm matrix of strong biofilm forming S. aureus strains in relation to different associated MLST CCs (a) and of strong biofilm forming strains associated with MLST CC1, CC5, CC8, CC22, CC30 and CC45 (b). R in Dimethyl sulfoxide the legend represents MRSA and S represents MSSA. Quantification of strains of the specified genetic background defined as strong biofilm former

at different glucose concentrations, (c) and (d). Asterisks denote statistically significant difference, (b) and (d), and statistical significant difference of individual CCs versus all other associated MLST CCs, (a) and (c), except #, (*) P < 0.05 and (**) P < 0.01. The main contributors to the higher prevalence of MRSA and MSSA with MRSA associated MLST CCs to produce strong biofilms at 0.1% glucose were MLST CC8 isolates, approximately 60% (26 of 41), (Figure 4c), especially with a tendency towards MRSA (Figure 4d). Additionally, blood stream isolates of MSSA associated with MLST CC8 and MLST CC7 were included in the study, to address the question whether the isolation site is an (additional) predisposing factor for strong biofilm formation.