Article Figures & Data
Figures
- FIG 1
Chemical structure of omadacycline.
- FIG 2
Effect of Tet(O) protein on the protein synthesis activity of omadacycline in vitro. Poly(U)-dependent Poly(Phe) synthesis (in vitro translation) was carried out in the presence or absence of purified Tet(O) added in a 1:1 molar ratio with ribosomes and various concentrations of either omadacycline or tetracycline. Percent activity relative to the control reaction (no omadacycline or tetracycline) is plotted.
- FIG 3
Ribosomal binding competition studies with [3H]tetracycline and unlabeled minocycline (A) or omadacycline (B). A series of tubes were prepared containing purified 70S ribosomes and increasing concentrations of the competitor test compound and a fixed concentration (3 μM) of [3H]tetracycline. Data are plotted as the log of the unlabeled competitor concentration in nM versus the percent binding relative to the reaction mixture containing no competitor. IC50 values were calculated by nonlinear curve fitting to a one-site competitive binding model and were determined to be 1.63 ± 0.01 μM (standard error) for minocycline and 1.96 ± 0.01 μM for omadacycline.
Tables
- TABLE 1
Activity of omadacycline against tetracycline-susceptible and -resistant strainsa
Strain Tetr determinant Mechanism type MIC (μg/ml) Omadacycline Tetracycline Doxycycline S. aureus RN450 None None 0.125 ≤0.06 ≤0.06 S. aureus ATCC 29213 None None 0.25 0.125 0.125 S. aureus MRSA5 Tet(M) Ribosomal protection 0.125 >64 4 S. aureus RN4250 Tet(K) Efflux 0.25 32 4 S. pneumoniae PBS382 Tet(O) Ribosomal protection <0.06 32 4 ↵a Antibacterial MICs were determined using CLSI methodology for antibacterial susceptibility testing. Tetracyline resistance determinants were confirmed by PCR as previously described (4).
- TABLE 2
Effect of omadacycline on macromolecular synthesis in susceptible and resistant S. aureus strainsa
Compound Strain Tetr MIC (μg/ml) IC50 protein synthesis (μg/ml) IC50 RNA synthesis (μg/ml) IC50 DNA synthesis (μg/ml) IC50 PG synthesis (μg/ml) Omadacycline RN450 None 0.125 <0.03 >32 >32 11.6 ATCC 29213 None 0.25 0.19 >32 >32 15.7 RN4250 tet(K) 0.25 0.08 >32 >32 >32 MRSA5 tet(M) 0.125 0.11 >32 >32 15.6 Tetracycline RN450 None <0.06 0.04 31.4 25.7 8.8 ATCC 29213 None 0.125 0.09 23.7 >32 7.6 RN4250 tet(K) 32 13.8 32 >32 22.7 MRSA5 tet(M) >64 1.8 >64 >32 >32 Doxycycline RN450 None <0.06 0.02 >32 >32 3.3 ATCC 29213 None 0.125 0.08 >32 >32 2.9 Rifampin RN450 None NT 0.01 0.01 >32 >32 ATCC 29213 None NT <0.01 0.01 >32 >32 Ciprofloxacin RN450 None 0.5 14.0 >32 0.4 >32 ATCC 29213 None 0.5 >32 >32 0.3 >32 Fosfomycin RN450 None NT >32 >32 >32 7.8 ATCC 29213 None NT >32 >32 >32 11.9 ↵a Antibacterial MICs were determined using CLSI methodology for antibacterial susceptibility testing. Tetracycline resistance determinants were confirmed by PCR as described in Materials and Methods. Macromolecular synthesis was performed as described previously (6, 7) and as described in Materials and Methods. Tetracycline and doxycycline are known protein synthesis inhibitors of the tetracycline class. Rifampin inhibits RNA polymerase, ciprofloxacin DNA synthesis, and fosfomycin peptidoglycan (PG) synthesis. The effects of rifampin on protein synthesis are secondary to the effects on RNA production (19). “Tetr” refers to the tetracycline-resistant element carried by the strain. IC50 data represent the calculated concentration of drug that reduces activity in the assay by 50% relative to the no-drug control. NT, not tested.
