https://orcid.org/0000-0002-3509-8111
Figures & data
Figure 1. Mechanism of target and resistance of β-lactam antibiotics. (A) Mechanism of β-lactam antibiotic action. (B) Mechanism of induction of staphylococcal β-lactamase synthesis in the presence of the β-lactam antibiotic penicillin. (1) The DNA-binding protein BlaI binds to the operator region (repressed transcription of RNA from blaZ and blaR1-blaI). In the absence of penicillin, β-lactamase is present at low levels. (2) The binding of penicillin to BlaR1 induces autocatalytic activation of BlaR1. (3–4) Active BlaR1 either directly or indirectly (by BlaR2) cleaves BlaI into inactive fragments (transcription of blaZ and blaR1-blaI). (5–7) β-Lactamase, (encoded by blaZ (5)), hydrolyzes the β-lactam ring of penicillin (6), rendering it inactive (7). (C) Synthesis of PBP2a proceeds similarly to that described for β-lactamase. Exposure of MecR1 to a β-lactam antibiotic stimulates MecR1 synthesis. MecR1 inactivates MecI (synthesis of PBP2a is allowed). MecI and BlaI are coregulators that affect the expression of PBP2a and β-lactamase.
Figure 2. SCCmec cassette structure in S. aureus (J1-J3 – joining region).
Figure 3. Structures of current SCCmec types. The mec and ccr gene complexes are shaded pink and blue, respectively. The figure is adapted from IWG-SCC commentary, 2009, ASM and Baig et al. (Citation2018) with authors permission.
Table 1. Current SCCmec types.