The highly distinct OprD mutational patterns that were conserved within the majority of unrelated CF P. aeruginosa isolates (Table 5), along with those associated with the highly polymorphic RND family of efflux proteins and regulators, showed no correlation to previously reported drug transporter or efflux pump activities uniformly affecting P. aeruginosa susceptibilities with respect to SMX-TMP, aztreonam, carbapenems, or other classes of antimicrobials (16, 17, 21, 39, 40). Here, OPRD1 is linked to cystic fibrosis.