Aims: To define a method that describes antimicrobial resistance of meta-populations of bacteria in both a quantitative and biologically meaningful way.
Methods and results: Using spiral plating and colony counting technology we obtained, from animal faecal samples, the density of Escherichia coli that grow at different concentrations of antibiotic. A mathematical description of this dose-response curve fitted the data well. The parameters of this model have biological meaning and the model allowed subtle differences between meta-populations to be detected.
Conclusions: This method, termed MPA (meta-population analysis), is practical and provides a useful quantitative description of antimicrobial resistance in a bacterial meta-population.
Significance and impact of the study: This study shows that resistance can be defined quantitatively. The method may be used in many epidemiological and clinical studies of antimicrobial resistance in animals and humans.