FIG 6 .

Results of whole-cell ELISA studies of 33 NTHi strains from different clinical situations and isolated from healthy carriers. The NTHi strains are shown on the x axis. These studies were performed in triplicate, and the error bars indicate the standard deviations from the means. An absorbance of 0.25 at a wavelength of 600 nm equals three times the background of this ELISA in this assay. Thirty-one of the 33 strains showed reactivity at least three times the background level of the assay (absorbance at 600 nm of 0.24). Two strains were either below or at that level. These results suggest that the majority of NTHi strains express the KDO epitope. All studies were performed in triplicate.