TABLE 2

IC50 values for the binding of the β-lactam antibiotics to the four native PBPs of S. aureus

β-LactamIC50 (μM)a
PBP1PBP2PBP3PBP4
Cefradine516 ± 69180 ± 73.0 ± 0.28,250 ± 280
Cephalexin374 ± 28154 ± 44.7 ± 0.48,108 ± 304
Cefepime1,059 ± 3830.3 ± 1.5>7,5002,346 ± 39
Ticarcillin147 ± 1522.4 ± 1.59.2 ± 0.3392 ± 26
Oxacillin42.2 ± 1.712.6 ± 0.910.4 ± 0.61,128 ± 90
Ertapenem89.7 ± 1.87.8 ± 0.582.8 ± 6.6233 ± 7
Cefotaxime88 ± 3.94.2 ± 0.1531 ± 502,567 ± 102
Ceftriaxone100 ± 63.8 ± 0.171.9 ± 5.38,906 ± 321
Imipenem2.7 ± 0.11.3 ± 0.13.9 ± 0.385.4 ± 2.4
Cefdinir104 ± 41.0 ± 0.12.5 ± 0.3126 ± 6
  • a IC50 reflects the concentration of β-lactam antibiotic that reduces the anisotropy (in the case of PBP1, PBP2, and PBP3) or initial anisotropy velocity (in the case of PBP4) of 1 μM Bocillin by 50%. The indicated uncertainties reflect the standard deviation of the experimental anisotropy data points in Figures 3 and S3 from the corresponding fitted curves.