Virulence of methicillin-resistant Staphylococcus aureus modulated by the YycFG two-component pathway in a rat model of osteomyelitis

Abstract

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) strains present an urgent medical problem in osteomyelitis cases. Our previous study indicated that the YycFG two-component regulatory pathway is associated with the bacterial biofilm organization of MRSA strains. The aim of this study was to investigate the regulatory roles of ASyycG in the bacterial biofilm formation and the pathogenicity of MRSA strains using an antisense RNA strategy. Methods: An ASyycG-overexpressing MRSA clinical isolate was constructed. The bacterial growth was monitored, and the biofilm biomass on bone specimens was examined using scanning electron microscopy and confocal laser scanning microscopy. Furthermore, quantitative RT-PCR (QRT-PCR) analysis was used to measure the expression of yycF/G/H and icaA/D in the MRSA and ASyycG strains. The expression of the YycG protein was quantified by Western blot assays. We validated the role of ASyycG in the invasive ability and pathogenicity of the strains in vivo using histology and peptide nucleic acid fluorescent in situ hybridization. Results: The results showed that overexpression of ASyycG lead to a reduction in biofilm formation and exopolysaccharide (EPS) synthesis compared to the control MRSA strains. The ASyycG strains exhibited decreased expression of the yycF/G/H and icaA/D genes. Furthermore, Western blot data showed that the production of the YycG protein was inhibited in the ASyycG strains. In addition, we demonstrated that ASyycG suppressed the invasive ability and pathogenicity of the strain in vivo using an SPF (specific pathogen free) rat model. Conclusion: In summary, the overexpression of ASyycG leads to a reduction in biofilm formation and bacterial pathogenicity in vivo, which provides a potential target for the management of MRSA-induced osteomyelitis.