Figure 2.

(a) The shape of the isoboles of equal effect illustrates that doxycycline and erythromycin have a synergistic interaction, as lower-dose drug combinations have the same effect as high-dose monotherapies. (b) Population-level growth inhibition of Escherichia coli exposed to different antibiotic concentrations. Experimental data (cross symbols) are represented with standard error bars, while solid lines represent predictions of the model (circles) described by equations (2.5a–d) with growth parameters: V_max = 2511.6 h⁻¹, K = 0.62 µg ml⁻¹, c = 1.8 × 10⁴ cells µg⁻¹, and inhibition parameters for eythromycin: κ₁ = 3.46 ml µg⁻¹ and κ₂ = 0.079 ml µg⁻¹ and for doxycycline: κ₁ = 0.068 ml µg⁻¹ and κ₂ = 0.198 ml µg⁻¹. (Online version in colour.)