Time-kill kinetics assay.

The kinetics of bacterial killing were determined as previously described (45), with minor modifications. A bacterial culture grown overnight was diluted in saline to 0.5 McFarland turbidity, followed by a further 1:50 dilution in LB. The cell culture was incubated at 37°C with either colistin, niclosamide, or combinations thereof at the desired concentrations to result in sets of culture tubes per designated time intervals. A 100-μl aliquot was obtained from each tubes at specified time intervals and plated on LB agar plates after serial dilution in phosphate-buffered saline (pH 7.2). Bacterial colonies were counted from the plates after incubation for 18 h at 37°C.