Study of the Relatedness of the Expression among Antibiotics Resistant Genes, Sigma B and Virulence Factors in Staphylococcus aureus

β-lactam antibiotics like methicillin were used to be the powerful weapon in fighting infections caused by Staphylococcus aureus. The emergence of methicillin-resistant S. aureus (MRSA) is one of the most serious infection control issues currently facing large hospitals worldwide. Glycopeptides such as vancomycin are the treatment of choice for infections due to MRSA. The first two clinical isolates of vancomycin-resistant S. aureus (VRSA) were recovered from patients coexisted with vancomycin-resistant enterococci (VRE) in U.S.A. on 2002. Transfer of vancomycin resistant determinants (van operon) from VRE to MRSA had been proved after the consequent investigations. The present proposal will focus on studying the issues listed below: 1. Study the mechanism and limitation of the transfer of vancomycin resistant determinants from VRE to S. aureus; 2. Study the signal transduction pathways triggered by vancomycin; 3. Look for van homologous genes in S. aureus; 4. Investigate whether the treatment of vancomycin is seemed as a stress to affect the expression of σB; 5. Investigate the expression of σB modulated virulence factors in VRSA under the treatment of vancomycin. To address those questions above, molecular and cellular biological techniques, biochemical approaches, Surface Plasmon Resonance (SPR), S. aureus genomic DNA microarray analyses, real-time PCR and proteomic analyses will be applied to this study. So far, we had successfully created VRSA by VRE-MRSA conjugation. To monitor the σB expression, the promoter of asp23, which is directly regulated by σB, is being fused with a lux reporter system. To evaluate the pathogenicity caused by different S. aureus strains, levels of cultured cell damage are investigated by trypan blue staining and LDH released from damaged cell. We do hope this study could contribute to the control of the infectious risk caused by VRSA.

Project ID:PC9706-0315
External Project ID:NSC96-2320-B182-014-MY3