TABLE 4

Comparison of MIC changes due to the expression of plasmid-borne adeABC, adeIJK, and acrAB genes

AntibioticMICa (μg/ml) for AG100AΩ (ΔlacY) expressing RND pump genes from:
pKY9790pHSG576 and pKY9790
pKY9790pKY-adeABCpKY-acrABpHSG576pKY-adeIJKpHSG-acrAB
Ampicillin2816248
Benzylpenicillin161664163232
Cloxacillin41001,0002400100
Oxacillin22001,0002400100
Cephaloridine288484
Cephalothin288484
Cefepime0.030.50.10.030.060.03
Nitrocefin262500212562
Erythromycin206401,0002040125
Rifampin163232321632
Novobiocin8252,0001620050
Tetracycline410025446
Minocycline15025246
Kanamycin444444
Gentamicin222222
Ciprofloxacin0.030.50.250.030.060.06
Norfloxacin0.252.02.50.120.300.31
Ethidium bromide204001,5002520050
  • a MICs for various antibiotics due to the expression of plasmid-borne adeABC, adeIJK, and acrAB genes were analyzed in E. coli AG100AΩ (ΔlacY), and changes in the MICs for kanamycin and gentamicin were analyzed in AG100AΩ. In order to adjust the levels of expression of the efflux pumps, the adeABC genes were induced with 10 μM IPTG and the adeIJK genes were induced with 5 μM IPTG. The acrAB genes in a low-copy-number plasmid were induced with 500 μM IPTG. MIC tests were performed as described in Materials and Methods.