Mechanism of β-lactam resistance of Staphylococcus aureus , Mechanism of methicillin resistance of Staphylococcus aureus
Mechanism of β-lactam resistance of Staphylococcus aureus β-lactamase enzymes cause resistance of cell to β-lactam antibiotics by inactivating β-lactam antibiotics. β-lactamase inactivates β-lactam antibiotics by disrupting amide bond of βlactam ring [5]. Expression of the blaZ gene that is located in plasmid or transposon and encodes β-lactamase is regulated by blaI and blaRI that are own regulators. In the lack of β-lactam antibiotic, BlaI that bound to promoter-operator region repress blaZ gene, blaI-blaRI operon, so transcription of blaZ is not happen. In the usage in treatment or supplementation of β-lactam antibiotic to growth media, β-lactam binds to BlaRI that is a β-lactam-sensing signal transducer, and then, intracellular zinc metalloprotease domain of BlaRI is separated and cleaves BlaI that is already bound to operator. By this way, in the presence of β-lactam, blaZ is transcribed to β-lactamase that permits MRSA to grow by inactivating β-lactam. (a). Induction of staph