In vitro activities of telithromycin against Staphylococcus aureus biofilms compared with azithromycin, clindamycin, vancomycin and daptomycin

Introduction. Staphylococcus aureus biofilms are difficult to treat and the effect of telithromycin treatment is still unclear. Aim. This study aimed to explore the effect of telithromycin against Staphylococcus aureus biofilms compared with azithromycin, clindamycin, vancomycin and daptomycin. Methodology. Eight methicillin-susceptible and eight methicillin-resistant S. aureus isolates (MSSA and MRSA, respectively) were used for this study. Biofilm biomasses were detected by crystal violet staining and the adherent cells in the established biofilms were quantified by determination of colony-forming units (c.f.u.). The RNA levels of biofilm formation-related genes were determined by RT-qPCR. Results. Telithromycin [8x minimum inhibitory concentration (MIC)] eradicated more established biofilms than azithromycin or clindamycin in the four MSSA isolates, and eliminated the established biofilms of six MRSA isolates more effectively than vancomycin or daptomycin. Telithromycin (8x MIC) killed more adherent cells in the established biofilms than azithromycin or clindamycin in the six MSSA isolates, and killed more adherent cells than vancomycin in all eight MRSA isolates. Daptomycin also showed an excellent effect on the adherent cells of MRSA isolates, with similarresults to telithromycin. The effect of a subinhibitory concentration of telithromycin (1/4x MIC) was significantly superior to that of azithromycin or clindamycin, inhibiting the biofilm formation of six MSSA isolates and seven MRSA isolates more effectively than vancomycin or daptomycin. The RNA levels of agrA, agrC, clfA, icaA and sigB decreased when treated with telithromycin (1/4x MIC). Conclusions. Telithromycin is more effective than azithromycin, clindamycin, vancomycin, or daptomycin against S. aureus biofilms.