Fig. 5

Disruption efficacy of endolysin LysSYL against mono-species biofilms of S. aureus and its persisters. Representative images of (A) 24 h and (B) 72 h S. aureus USA300 biofilms treated with 1× MIC LysSYL for 1 and 5 h, respectively. 32×MIC VAN treatment served as positive control, and PBS used as negative control. Eradication of (C) 24 h- and (D) 72 h-old S. aureus mono-species biofilms with various concentrations of LysSYL for 1 and 5 h, respectively. The biofilm mass in each well was determined by crystal violet assay. VAN and PBS were used as positive and negative controls, respectively. The experiment was repeated three times. Data were expressed as mean ± SD. The statistical analysis was measured by one-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001, and ns indicates no significance. E Bactericidal activity of LysSYL against S. aureus cells in the biofilms. The number of viable bacteria in the 24 h-old biofilms were counted after treatment with various concentrations of LysSYL for 1 h. VAN served as positive control. The experiment was repeated three times. Data were expressed as mean ± SD. The statistical analysis was measured by two-way ANOVA. ***P < 0.001, and ns indicates no significance. F Bactericidal activity of LysSYL against S. aureus persisters. Time-kill kinetic graph showing S. aureus USA300 cells initially killed with 100×MIC VAN or 100×MIC CEF to achieve a constant number of persisters. Then 4×MIC LysSYL was added at 24 h to remove antibiotic-tolerant persisters. Experiments were repeated three times. Data were expressed as mean ± SD.