FIG 1.

The IPM^S/AGS^S population is susceptible to both imipenem and the aminoglycoside, the IPM^R/AGS^I population is imipenem resistant and has intermediate susceptibility to the aminoglycoside, and the IPM^I/AGS^R population is aminoglycoside resistant and has intermediate susceptibility to imipenem. The maximum killing rate constants (K_max) and the antibiotic concentrations causing 50% of K_max (KC₅₀) are explained in Table 3. The effect of aminoglycosides on the outer membrane (i.e., the aminoglycoside enhancing the target site penetration of imipenem) was applied to all three strains. The outer membrane effect terms I_max,OM and IC_50,OM are explained in Table 3. A life cycle growth model (61, 64) was utilized for each of the three populations to describe bacterial growth and replication.