RESUMO
Increasing cases of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains in healthy individuals have raised concerns worldwide. MRSA strains are resistant to almost the entire family of ß-lactam antibiotics due to the acquisition of an extra penicillin-binding protein, PBP2a. Studies have shown that spoVG is involved in oxacillin resistance, while the regulatory mechanism remains elusive. In this study, we have found that SpoVG plays a positive role in oxacillin resistance through promoting cell wall synthesis and inhibiting cell wall degradation in MRSA strain N315. Deletion of spoVG in strain N315 led to a significant decrease in oxacillin resistance and a dramatic increase in Triton X-100-induced autolytic activity simultaneously. Real-time quantitative reverse transcription-PCR revealed that the expression of 8 genes related to cell wall metabolism or oxacillin resistance was altered in the spoVG mutant. Electrophoretic mobility shift assay indicated that SpoVG can directly bind to the putative promoter regions of lytN (murein hydrolase), femA, and lytSR (the two-component system). These findings suggest a molecular mechanism in which SpoVG modulates oxacillin resistance by regulating cell wall metabolism in MRSA.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/metabolismo , Parede Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , N-Acetil-Muramil-L-Alanina Amidase/genética , Oxacilina/farmacologia , Proteínas de Bactérias/genética , Bacteriólise/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Ensaio de Desvio de Mobilidade Eletroforética , Staphylococcus aureus Resistente à Meticilina/genética , Octoxinol/farmacologia , Regiões Promotoras Genéticas/genética , Fatores de Transcrição/metabolismoRESUMO
We report a new strategy for differential delivery of antimicrobials to bacterial infection sites with a lipase-sensitive polymeric triple-layered nanogel (TLN) as the drug carrier. The TLN was synthesized by a convenient arm-first procedure using an amphiphilic diblock copolymer, namely, monomethoxy poly(ethylene glycol)-b-poly(ε-caprolactone), to initiate the ring-opening polymerization of the difunctional monomer 3-oxapentane-1,5-diyl bis(ethylene phosphate). The hydrophobic poly(ε-caprolactone) (PCL) segments collapsed and surrounded the polyphosphoester core, forming a hydrophobic and compact molecular fence in aqueous solution which prevented antibiotic release from the polyphosphoester core prior to reaching bacterial infection sites. However, once the TLN sensed the lipase-secreting bacteria, the PCL fence of the TLN degraded to release the antibiotic. Using Staphylococcus aureus (S. aureus) as the model bacterium and vancomycin as the model antimicrobial, we demonstrated that the TLN released almost all the encapsulated vancomycin within 24 h only in the presence of S. aureus, significantly inhibiting S. aureus growth. The TLN further delivered the drug into bacteria-infected cells and efficiently released the drug to kill intracellular bacteria. This technique can be generalized to selectively deliver a variety of antibiotics for the treatment of various infections caused by lipase-secreting bacteria and thus provides a new, safe, effective, and universal approach for the treatment of extracellular and intracellular bacterial infections.