FIGURE 4.

Biofilm biomass, metabolic activity, and CFU analysis of 48-h-old Staphylococcus aureus ATCC 6538 biofilm after treatment with different concentrations of single/combined antibiotics. The biofilm biomass and metabolic activity were evaluated using crystal violet staining and the XTT reduction assay, respectively, after 48 h of treatment with (A,B) tedizolid alone (lines with filled dots) or in combination with rifampicin (dashed lines with filled triangles) and (C,D) daptomycin alone (lines with empty triangles) or in combination with rifampicin (dashed lines with filled squares). Results from three independent experiments in triplicate are expressed as percentage ± SEM with respect to the untreated control biofilm. Statistically significant differences were tested with ordinary one-way ANOVA or Kruskal–Wallis test. *p < 0.05 biofilm treated with single antibiotic vs untreated control biofilm. ^#p < 0.05 biofilm treated with combination of antibiotics vs untreated control biofilm. (E) Evaluation of bacteriostatic and bactericidal activities of biofilms treated with various antibiotic combinations (C = control untreated biofilm, BS = bacteriostatic effect threshold, BC = bactericidal effect threshold).