Pilus-Mediated Adherence ofHaemophilus influenzaeto Human Respiratory Mucins

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Abstract
Haemophilus influenzae, especially the nontypeable strains, are among the most common pathogens encountered in patients with chronic lung disease and otitis media. We and others have demonstrated that respiratory isolates of nontypeableH. influenzaebind to human mucins, but the mechanism of binding is not entirely clear. We have therefore examined the role of pili in the adherence of both type b and nontypeableH. influenzaeto human respiratory mucins. We used isogenicH. influenzaestrains with a mutation in the structural gene for pilin (hifA), a laboratoryH. influenzaestrain transformed with a type b pilus gene cluster (from strain C54), antibodies raised againstH. influenzaeHifA, andEscherichia colistrains carrying a cloned type b pilus gene cluster (from strain AM30) in these studies. All bacteria lacking HifA or the pilus gene cluster had decreased adherence of piliatedH. influenzaeto mucins, and Fab fragments of anti-HifA antibodies inhibited the adherence.E. colistrains carrying the cloned type b pilus gene cluster were six to seven times more adhesive than strains carrying the vector. The role of other putative adhesins was not examined and thus cannot be excluded, but these studies support a role for pili in the binding ofH. influenzaeto human respiratory mucins.