FIG. 6.

Plot of the first two principal components resulting from PCA of all 12 antimicrobial agents for species selected to demonstrate differences in PCA, with points labeled as wildlife (w), swine (s), and human (*) (the line indicates the division between low- and high-susceptibility groups for nalidixic acid, the oval indicates the high-tetracycline-susceptibility group, the rectangle indicates high sulfisoxazole susceptibility alone, and the hexagon indicates the low-susceptibility group).