Staphylococcus aureus biofilm organization modulated by YycFG two-component regulatory pathway

Shizhou Wu,Hui Zhang,Fuguo Huang,Lei Lei

doi:10.1186/s13018-018-1055-z

Abstract

BackgroundStaphylococcus aureus (S. aureus) infection accounts for more than 50% of the osteomyelitis cases. Currently, methicillin-resistant S. aureus (MRSA) strains present an urgent medical problem. The YycFG two-component regulatory system (TCS) can allow bacteria to rapidly adapt to physical, chemical, and biological stresses. To define the role of YycFG in modulation virulence of S. aureus in osteomyelitis, we isolated clinical MRSA strains and compared these with ATCC29213 methicillin-sensitive S. aureus (MSSA).MethodsIn the present study, 13 MRSA strains from chronic osteomyelitis tissues were isolated. The in-depth sequencing of 16S rRNA amplicons of the samples was conducted. Bacterial growth was monitored, and biofilm biomass was determined by crystal violet microtiter assay. Furthermore, quantitative RT-PCR analysis was adopted to identify the expression of yycF/G/H and icaA/D in MRSA and MSSA strains. Analysis of variance with one-way ANOVA was used for statistical analysis.ResultsThe in-depth sequencing of 16S rRNA amplicons of the clinical samples indicated a polymicrobial infection, with the phylum Firmicutes made up 13% of the microbial population. The MRSA strains showed an accelerated growth rate compared to the MSSA strains. Of note, MRSA biofilms showed an accumulation of an intercellular polysaccharides matrix and enhanced biomass upon microscopic examination. Furthermore, MRSA strains had a higher expression of the yycF/G/H and icaA/D genes and adhesion force.ConclusionsThese data suggested the roles of intercellular polysaccharide in S. aureus pathogenesis, indicating a possible association between YycFG pathways and MRSA strain virulence.

Highlights

Osteomyelitis is a progressive infection of the bone, resulting in destruction of bone tissue and bone necrosis, eventually developing into a chronic or persistent condition [1]
Chronic osteomyelitis is the prominent type of osteomyelitis with high recurrent rates, which may result from tenacious biofilms formed by Staphylococcus aureus (S. aureus), Streptococcus pyogenes, Streptococcus
The growth curves of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains were compared in three independent experiments

Summary

Introduction

Osteomyelitis is a progressive infection of the bone, resulting in destruction of bone tissue and bone necrosis, eventually developing into a chronic or persistent condition [1]. The annual incidence of invasive bone and joint methicillin-resistant Staphylococcus aureus (MRSA) infections accounts for 2.8 to 43% of all invasive MRSA infections which make up 1.6 to 29.7 cases per 100,000 osteomyelitis cases [6]. The YycFG two-component regulatory system (TCS), specific to low G+C Gram-positive bacteria such as Bacillus subtilis, S. aureus, Enterococcus faecalis, and Streptococcus mutans, mediates the synthesis of biofilms that allows bacteria to rapidly adapt to physical, chemical, and biological stresses. Mutations in the YycFG TCS have been associated with resistant and persistent infections [2, 8]. We tracked the MRSA from chronic osteomyelitis cases and methicillin-sensitive Staphylococcus aureus (MSSA) strains to investigate the potential roles of YycFG TCS components. To define the role of YycFG in modulation virulence of S. aureus in osteomyelitis, we isolated clinical MRSA strains and compared these with ATCC29213 methicillin-sensitive S. aureus (MSSA)

Methods

Results

Conclusion