FIG 5.

Preexposure to BKC increases CHX resistance. (A and B) RN4220 (pCN38-qacA qacR) was grown to log phase and exposed to either H₂O (vehicle control) or BKC for 60 min. Cells were then washed and inoculated into the indicated concentration of CHX. CFU were determined immediately following inoculation and at 60 and 120 s. (C and D) C02 was grown to log phase and exposed to either H₂O (vehicle control) or BKC for 60 min. Cells were then washed and inoculated into the indicated concentration of CHX. CFU were determined immediately following inoculation and at 90 and 180 s. Percent survival was calculated as (CFU at N seconds/CFU of input) × 100, where N equals indicated chlorhexidine exposure times. Graphed values for percent survival are from ≥5 independent replicates, and the bars indicate the geometric means. The open square represents a replicate for which no bacteria were recovered and is graphed at the limit of detection. The P values above the graphs indicate statistically significant differences as determined by Student t test with a correction for multiple comparisons using the Holm-Sidak method.