TABLE 4.

Persister specificitya

Time of antibiotic exposureNo. of bacteria (CFU/ml)
AntibioticW3110JHU-313
0 h5 × 1071.4 × 107
1.5 hAmpicillin7 × 1044 × 104
20 hAmpicillin7 × 1050
Gentamicin5 × 1052 × 103
Trimethoprim6 × 1056 × 105
Norfloxacin7 × 1050
  • a Cells were grown in LB to the exponential phase, at which point they were exposed to ampicillin 100 μg/ml. Values for 0 h are starting CFU values. After exposure to ampicillin for 1.5 h, cells were washed by centrifugation and resuspended in LB containing gentamicin 20 μg/ml, trimethoprim 16 μg/ml, norfloxacin 5 μg/ml, and again ampicillin 100 μg/ml and incubated for 20 h. CFU was determined at the start, after 1.5 h ampicillin treatment and at 20 h after second antibiotic exposure.