TABLE 3.

Susceptibility of all strains and isolates to fluoroquinolones and dyes

Agent and efflux inhibitoraMIC (μg/ml) forb:
Wild-type strainFQDR isolatesFQ-R isolatesDR isolatesS isolates
M3M4R6RangeMIC90RangeMIC90RangeMIC90RangeMIC90
Cip110.52-64161-6480.25-0.250.250.25-0.50.25
Cip + res0.50.50.50.5-3240.5-6440.5-0.50.50.25-10.5
Cip + NaO110.10.12-6480.12-3220.5-0.50.50.12-10.5
Nor48416-643216-32324-442-44
Nor + res2421-1682-1681-111-21
EtBr2214-1681-8216-16161-42
EtBr + res0.50.30.30.12-0.50.50.12-40.50.5-0.50.50.06-0.50.25
EtBr + NaO0.30.30.10.12-210.06-40.51-110.06-10.25
Acr4428-1682-4416-16162-44
Acr + res1110.25-210.25-40.52-220.25-21
Acr + NaO0.50.50.30.25-210.25-20.52-220.25-10.5
  • a Cip, ciprofloxacin; Nor, norfloxacin; EtBr, ethidium bromide; Acr, acriflavine; res, reserpine; NaO, sodium orthovanadate.

  • b FQDR, resistant to both fluoroquinolones and dyes (n = 15); FQ-R, resistant to fluoroquinolones alone (n = 24); DR, dye resistant (n = 2); S, susceptible to all agents (n = 16). MICs of each agent in the absence of an efflux inhibitor are highlighted in boldface.