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
External Project ID:NSC102-2320-B182-021
Status | Finished |
---|---|
Effective start/end date | 01/08/13 → 31/07/14 |
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