Table 3.

Influence of the cloned oprM andmexAB genes on the antibiotic susceptibility of P. aeruginosaa

Strain/plasmidMIC (μg/ml)b
CARCPZCEFCPMNORCIPNOVERYTETIMP
PAO66093241210.25256512161
K1032/pMMB20610.50.250.250.250.03166411
K1032/pQZ0510.510.510.121651221
K1032/pQZ0610.50.250.250.250.03166411
K1032/pQZ05 + pQZ0632410.5–110.2525651281
PAO1328110.50.2525625616c
K1119/pMMB20640.50.060.060.120.12641280.5
K1119/pQZ0540.50.510.250.05645128
ML5087328110.50.2551225616
K1121/pMMB20610.50.250.250.250.124641
K1121/pQZ0510.5110.50.2545128
K1115/pMMB20610.50.250.1250.250.124641
K1115/pQZ0510.50.50.50.50.2545128
  • a The ΔmexAB-oprM strains K1032 (derived from PAO6609), K1119 (derived from PAO1), and K1121 (derived from ML5087) and the ΔmexAB-oprM ΔmexCD-oprJstrain K1115 (derived from ML5087) were reconstituted with the pMMB206-derived oprM (pQZ05) and mexAB (pQZ06) plasmids, and the influences on antibiotic susceptibilities were assessed as outlined in Materials and Methods.

  • b CAR, carbenicillin; CPZ, cefoperazone; CEF, cefepime; CPM, cefpirome; NOR, norfloxacin; CIP, ciprofloxacin; NOV, novobiocin; ERY, erythromycin; TET, tetracycline; IMP, imipenem. Twofold differences were confirmed as significant by performing agar diffusion assays where the more susceptible strain elicited a zone of inhibition which was ≥25% larger than that of the more resistant strains at a set concentration of antibiotic.

  • c Not determined.