A retrospective analysis of patients receiving ciprofloxacin indicated that an AUC/MIC ratio of approximately 100 was required to prevent resistance (7). However, there were some flaws in this study and the ratio required may be higher. We have investigated this in a mouse-thigh infection model, which simultaneously modeled the effect of differing drug exposures with levofloxacin on the total bacterial population. The effect of differing drug exposures was also modeled on a more resistant population.

Population modeling techniques were then used to identify a total drug AUC/MIC ratio of approximately 157 as required to shut off amplification of the resistant mutant population (7).