Traditionally reporting of antimicrobial susceptibility testing (AST) results to clinicians has been in the form of clinical interpretive breakpoints i.e. S = susceptible, I = intermediate, R = resistant. These interpretive breakpoints have largely been derived from microbiological, pharmacological and clinical data and have served the purpose of providing clinicians with relatively accurate data as to what may constitute appropriate treatment for a specific pathogen. 

Unfortunately the treatment of infectious diseases has become more complicated over time with the increase in antimicrobial resistance threatening to render antibiotics obsolete. It is in this context that the need for actual minimum inhibitory concentrations (MIC) has arisen. The provision of an MIC allows tailoring of antimicrobial treatment through the application of pharmacodynamic (Pd) and pharmacokinetic (Pk) principles. The aim is thus to optimize treatment of an infectious disease and eliminate unwanted side effects by choosing an agent with an appropriate spectrum of activity, at the correct dose, frequency of administration, and for the correct duration. This is in alignment with the principles of antibiotic stewardship and effective application of these principles often requires an MIC.

This is the first Edupath in a series to explain and highlight the value of the MIC.

Contact author