In our recent webinar titled “PK-PD in support of accelerated programmes for antimicrobial development: how much is enough?” with William Hope, we received more questions from the audience than we could answer during the session. We will now follow up on some remaining questions in the forum and encourage our experts but also users to discuss these questions.
I will suggest looking at the following open access publication: Statistical characterisation of bacterial wild-type MIC value distributions and the determination of epidemiological cut-off values: https://doi.org/10.1111/j.1469-0691.2006.01377.x
Pharmacodynamics (PD) relates concentration of an antibacterial to effect, specifically to its antimicrobial effect, and its goal is to find a dose of drug that has a high probability of therapeutic success while also trying to balance it with acceptable toxicity.
Therefore, what matters most is the antimicrobial susceptibility of the target bacterial population as a whole. In that respect MIC50 and MIC90 values provide only a limited insight into which isolates might represent the wild-type population and which isolates harbour acquired resistance.