Figure 1. Isolation of persister cells from S. aureus planktonic populations.

Stationary-phase planktonic cultures were exposed to saline or ciprofloxacin in saline for a period of 24 h (A). Cell viability was determined at 0, 1, 3, 6 and 24 h. To confirm that only persister cells were present, cultures were washed and isolated persister cells were exposed to saline or ciprofloxacin in saline for 24 h (B). Persister cells were also re-grown in LB medium and recovered survivors were re-challenged with ciprofloxacin for a period of 24 h (B). The averages of data from 3 experiments with 2 replicates per experiment are shown. Error bars indicate standard deviations (*P < 0.001- significantly different from cells exposed to saline alone, as indicated by one-way ANOVA).