Table 2

Activity of fluoroquinolones against E. coli mutants

LineStrain*C8-OMeC8-HC8-OMe/C8-H
ID50, μg/ml
1DM4100 (WT)0.12  ±  0.030.039  ±  0.0063
2GP201 (gyrAR)1.2  ±  0.070.82  ±  0.0391.5
3KD1366 (gyrARparCR)2.1  ±  0.273.1  ±  0.130.67
ID50 ratio
4GP201/DM41001021
5KD1366/GP2011.83.8
% survivors at 5-fold ID50§
6DM4100 (WT)0.071.151/16
7GP201 (gyrAR)0.116.31/57
  • * WT, wild type; gyrAR, NalR; parCR, CipR

  • Fluoroquinolones tested were PD161148 (C8-OMe) and PD160793 (C8-H). Values of ID50 are means ± SD. 

  • Nearly identical results were obtained for the gyrAR parCR strain KD1368. 

  • § Cells were treated with fluoroquinolone for 1 hr, after which they were diluted and plated on LB agar. Colonies were counted after 16 hr of incubation at 37°C.