Identification of a specific epitope of Haemophilus influenzae on a 16,600-dalton outer membrane protein

A mouse monoclonal antibody that recognizes an epitope on a 16,600-dalton outer membrane protein was developed to nontypable Haemophilus influenzae. This epitope was present on all 115 isolates of H. influenzae tested, including typable and nontypable strains. Screening of 89 strains of other bacteria demonstrated that this epitope is a highly specific marker for H. influenzae because the epitope was absent in virtually all other bacterial species tested. Western blot assays were performed with two normal human serum samples and convalescent-phase serum from an adult with bacteremia due to nontypable H. influenzae. Antibody to the 16,600-dalton outer membrane protein was present in all three human serum samples.