The Effect of Glucose on Vancomycin-Enhanced Biofilm Formation by Vancomycin-Resistant Staphylococcus aureus

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

Staphylococcus aureus is a major healthcare-associated and community-acquired pathogen worldwide. The increase in multidrug-resistant S. aureus (MDRSA) strains has become a serious clinical challenge because it limits therapeutic options. We are interested in studying the role of an antibiotic when applied to a resistant S. aureus strain. Our previous results showed that antibiotics that target the cell wall (such as vancomycin) and SXT in a sub-lethal dose may act as environmental stressors to induce σB activity in drug-resistant strains. We were especially interested in the stress response in vancomycin-resistant S. aureus (VRSA) strains treated with vancomycin. Vancomycin-induced σB activity altered the expression of downstream virulence factors and the increase in cytotoxicity upon vancomycin treatment was observed. We then demonstrated that sub-lethal doses of cell wall-active antibiotics like vancomycin induced biofilm formation through an autolysis- dependent mechanism in vancomycin-non-susceptible S. aureus. New findings in this laboratory showed that vancomycin further enhanced biofilm formation of VRSA in a higher glucose concentration but changed its role to become a biofilm destroyer in the depletion of glucose. Those in vitro results imply that the improper antibiotic treatment to the potential drug-resistant bacteria may lead to worse outcomes in clinical environments and the consequences in vivo will be studied in this project. Patients with diabetes are predisposed to chronic infections which are somehow associated with biofilm formation. Whether patients with diabetes offer a higher glucose concentration environment to further promote vancomycin-enhanced biofilm formation upon S. aureus infection will be investigated in a diabetic mouse model. Diabetes in mice will be induced by intraperitoneal injection of streptozotocin (STZ) followed by an in vivo catheter-association biofilm formation assay. Molecular mechanisms that vancomycin-enhanced biofilm formation is further stronger in a higher glucose concentration will be investigated by determining the expression levels of biofilm development genes using real-time quantitative reverse transcription PCR (qRT-PCR). In the depletion of glucose, vancomycin triggers staphylococcal biofilm disassembly suggesting the release of biofilm degrading products by VRSA to the medium. Those potential products will be identified by SDS-PAGE followed by mass spectrometry for proteins and HPLC assay for phenol-soluble modulins (PSMs). The impact of proteases and nucleases on biofilm disassembly will be investigated by functional assay. Molecular mechanisms underlying vancomycin-triggered biofilm disassembly will be investigated by determining the expression levels of biofilm disassembly-associated genes using qRT-PCR. This study is expected to further understand the interplay between improper antibiotic treatment for drug-resistant bacteria and host response.

Project IDs

Project ID:PC10207-0069
External Project ID:NSC102-2320-B182-021
StatusFinished
Effective start/end date01/08/1331/07/14

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