FIG 4.

Viable cell counts for different strains under antibiotic stress. Mid-log-phase cells were grown in either the absence or presence of various antibiotics (cefotaxime, 100 μg/ml; ciprofloxacin, 0.4 μg/ml; ampicillin, 100 μg/ml; kanamycin, 50 μg/ml; and tobramycin, 25 μg/ml) in a 96-well microtiter plate. Viable cell counts were measured at intervals of 30 min for 5 h and plotted against time. The average readings from three independent replicates are shown. For clarity, only data at hourly intervals are presented.