Multiple Low Frequency Ultrasound Enhances Bactericidal Activity of Vancomycin against Methicillin-Resistant Staphylococcus aureus Biofilms

Figure 4

Synergistic effect of M-LFU and vancomycin against MRSA or MSSA biofilms. (a) Comparison of synergistic effects of S-LFU and M-LFU combined with vancomycin against MRSA or MSSA biofilms. S-LFU irradiation time was set to 5 and 15 min and M-LFU was set to5 min every 8 hours for 24 hours. With fixed intensity (92.36 mW/cm²), the synergistic effects of S-LFU and M-LFU in combination with 4×MIC vancomycin were investigated. The viable bacterial counts in biofilms were determined at 24 hours following ultrasound treatment. VAN refers to vancomycin. <0.05, as compared with control, vancomycin treatment without S-LFU or M-LFU group. (b) The effect of vancomycin concentration on the synergistic effect of vancomycin and ultrasound. With irradiation time adjusted to 5 min every 8 hours for 24 hours and fixed intensity (92.36 mW/cm²), M-LFU in combination with 1, 2, and 4×MIC vancomycin was used to treat the biofilms. The viable bacterial counts in biofilms were determined at 24 hours. VAN refers to vancomycin. <0.05, as compared with vancomycin treatment without M-LFU group.

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