FIG. 4.
Polymyxin assay. The graph shows the MICs of polymyxin necessary to inhibit the growth of the different strains. The MIC was considered the lowest drug concentration that reduced growth >50% compared with the growth in the control well. The MICs of polymyxin for strains χ7122 (wild type), K3 (ΔpstCAB::kan), and CK3 [K3(pAN92)] are shown. The MIC for the pst mutant strain K3 was significantly lower than that for the wild-type χ7122 strain (P < 0.001). The MIC differences between the complemented strain CK3 and either strain χ7122 or strain K3 were significant (P = 0.044).