Haemophilus influenzae, a normal host of the nasopharynx of humans, may become a pathogen. The first step of
infection is adherence to epithelial cells of the nasopharynx through glycopeptidic adhesins, or pili. Adherence to human epithelial cells in continuous lines, HeLa and Hep2, of 8 piliated strains of Haemophilus influenzae isolated from human
infections of the respiratory tract was studied in vitro in the presence of
fusafungine, a local bacteriostatic
antibiotic. When the bacteria were grown in the presence of 0.5 x the MIC,
fusafungine afforded 45-75% of adherence inhibition, but this inhibitory effect did not parallel the MICs. In contrast, no significant effect could be observed either when epithelial cells were exposed to 0.5 x the MIC before use in the adherence assay, or when this assay was performed in the presence of 0.5 x the MIC of
fusafungine. The partial adherence inhibition observed suggests that
fusafungine interacts with the bacterial binding sites but that other mechanisms may contribute to the inhibitory process. This effect of
fusafungine should prevent but not eradicate colonization of the nasopharyngeal mucosa by Haemophilus influenzae and may account for the therapeutic efficacy reported in
infections of the respiratory tract due to Haemophilus influenzae.