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Table 1 Estimation of primary and secondary PD parameters obtained from a model of the time kill experiment of TYL against S. delphini

From: Evaluating a tylosin dosage regimen for treatment of Staphylococcus delphini infection in mink (Neovison vison): a pharmacokinetic-pharmacodynamic approach

Parameter Units S. delphini
Mean SE
Primary parameters
 Kel 1/h 0 (fixed)
 Kgrowthmax 1/h 0.63 0.017
 Kdeath 1/h 0.17 (fixed)-
 Bmax CFU/mL 4.8 × 109 4.2 × 108
 Emax 1/h 0.75 0.022
 Gamma Scalar 2.73 0.275
 EC50 mg/L 0.55 0.026
 SD Scalar 1.16 0.079
 IIV Bmax (CV%) 878 0.604
 η shrinkage Bmax 0.02  
Secondary parameters
 MIC mg/L 0.36 0.023
 MBC mg/L 1.45 0.049
  1. Kel is the drug degradation rate constant fixed as 0 to express no degradation of TYL during 24 h in a test tube, Kgrowthmax is the maximum growth rate constant of bacterial strains, Kdeath is the natural death rate constant of a bacterial strain that is equally present in the S and P compartments and was considered at a fixed rate of 0.17 per hour, Bmax is the total bacterial count in the system (S + P), Emax is the maximal effect of drug against bacterial species assessed by a maximal killing rate (efficacy), gamma (γ) is the curve slope, EC50 is the concentration of drug that produces half of the maximal effect, SD is standard deviation of the residual (exponential model for the control curves), IIV is inter-individual (i.e. curve) variability expressed as coefficient of variation (CV%), this variability corresponded to estimated post-hoc values of Bmax from 1.86 × 108 to 3.58 × 1010 for the 6 curves, Shrinkage refers to the quality of the estimated IIV, MIC and MBC are minimum inhibitory and bactericidal concentration of drug against bacterial species as estimated by the model. The precision of parameters (SE) was computed by the bootstrap tool in Phoenix®.