TABLE 3.

Drug resistance of E. coli cells harboring plasmids carrying acrB or acrD in acrAB, acrB, or tolC deletion mutant

DrugMIC (μg/ml) for strain with indicated transporter overexpressiona
KAM3 (acrA+acrB tolC+)TG1 (acrA+acrB+tolC+) (None)TG1ΔacrAB (acrA acrB tolC+)TG1 ΔtolC (acrA+ acrB+ tolC)
NoneAcrBbAcrDcNoneAcrBAcrDNoneAcrD
Acriflavine12.5100NDd40012.512.5NDNDND
Crystal violet0.7825ND250.780.78NDNDND
Enoxacin0.050.20ND0.200.050.05NDNDND
Erythromycin3.1350ND503.133.13NDNDND
Ethidium bromide12.5>400ND>40012.512.5NDNDND
Minocycline6.2512.5ND12.56.256.25NDNDND
Nalidixic acid0.393.13ND3.130.390.39NDNDND
Norfloxacin0.050.10ND0.100.050.05NDNDND
Novobiocin1.561003.131001.561.561.561.561.56
SDS50>400400>4005050502525
Tetracycline1.563.13ND3.131.561.56NDNDND
TPP6.25>400ND>4006.256.25NDNDND
Deoxycholate1,250>40,00020,000>40,0001,2501,2501,2507878
Benzalkonium3.1350ND503.133.13NDNDND
Rhodamine 6G6.25>400ND>4006.256.25NDNDND
  • a Values in boldface are larger than the control strain values.

  • b AcrB His tagged at the C terminus was overexpressed under control of the T5 promotor in the pQE70 vector.

  • c AcrD His tagged at the C terminus was overexpressed under control of the trc promotor in the pTrc6His vector (16).

  • d ND, not determined.