Study On Phenotype And Mechanism Of Vancomycin Induce Biofilm Formation In Staphyloccocus Aureus

Objective: Vancomycin is the primary choice for treatment of methicillin-resistant S.aureus(MRSA) infections. Reduced susceptibility to vancomycin have been a major challenges in modern clinical medicine because of the widespread use of vancomycin.In recent years, hVISA is increasingly reported, and is commonly associated with vancomycin treatment failure and persistent infection, however, the mechanism for treatment failure has yet to be determined. In this study, one hVISA clinicalisolate10827 was induced by different concentrations of vancomycin, we investigated the biofilm formation ability and the expression of related genes between hVISA and the series of induced vancomycin resistant strains, to explore the mechanisms involved in vancomycin induce biofilm formation inStaphyloccocus aureus.Methods:(1) The parental strain 10827 was continuous passage induced by different concentrations of vancomycin, and the vancomycin MIC values were detected by E-test.(2) The proliferation ability of all strains were investigated by colorimetric assay.(3) The biofilm formation ability of the parent strain and the series of induced resistant strains were investigated by 96-well microplate assay.(4) The biofilm morphous was observed by scanning electron microscopy.(5) Expression of biofilm formation-related genes was investigated by real-time reverse-transcription PCR(qRT-PCR).Results:(1) The parental strain 10827 was induced to a series laboratory-induced vancomycin resistant strains by the in vitro induction method. According to the vancomycin MIC values, ??the series of induced vancomycin resistant strains were named 10827-V8, 10827-V16, and 10827-V32, respectively.(2) With elevatedvancomycin MIC values, the series of induced vancomycin resistant strains exhibiteddecreased growth rate,increased biofilm formation ability, upregulation of fnbA, icaA, atlA, and sarA and downregulation of icaR,comparable to the parental strain.(3) Scanning electron microscopy revealed that the induced strains, with elevated vancomycin MICs, exhibited cell-surface-associated meshwork-like structures and rough cell surfaces.Conclusions:(1) Vancomycin could induced hVISA to a series of vancomycin-induced resistant strains by the in vitro induction method, in the process of induction, the series of induced resistant strains exhibited increased biofilm formation ability.(2) The expression of fnbA, icaA, icaR, atlA and sarA may contribute to enhanced biofilm formation in the series of vancomycin-induced resistant strains.