A subtyping system for nontypable Haemophilus influenzae based on outer-membrane proteins

Outer-membrane proteins from 48 isolates of nontypable Haemophilus influenzae from adults and children were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the biotypes were determined. Each strain had two principal outer-membrane proteins in the 32,000-42,000 molecular-weight range. Eight subtypes were identified based on the differences in molecular weights of the two principal outer-membrane proteins. The lower molecular-weight protein of those two major proteins was heat modifiable. There was no definite relationship between subtype and biotype. Future studies on the pathogenesis and epidemiology of infections due to nontypable H. influenzae must take into account the differences in outer-membrane proteins among various strains. A subtyping system based on major outer-membrane proteins may provide a basis for such studies.