FIG. 1.

(A) Biofilm initiation by H. influenzae strains. Comparable numbers of bacteria were inoculated into microtiter dishes, washed, and stained with crystal violet. The density of bacteria remaining within the wells was estimated on the basis of the absorbance of ethanol-solubilized crystal violet at 540 nm (Abs. 540) (see Materials and Methods). P. aeruginosa PAO1 and wfpa60 were included as positive and negative controls, respectively. (B) Biofilm formation by NTHi 2019 in a continuous-flow silicon tubing system. Sterile silicon tubing was seeded with NTHi 2019 (see Materials and Methods) and incubated at 37°C with a continuous flow of supplemented BHI medium for 48 h.