Outer-membrane protein and immunoblot analysis of Australian isolates of Haemophilus influenzae.

Strains of Haemophilus influenzae isolated from children in South Australia and the Northern Territory with systemic infections (mostly meningitis or epiglottitis) were subjected to serotyping, biotyping, outer-membrane protein (OMP) analysis and immunoblot subtyping. All 65 isolates examined were from blood or cerebrospinal fluid; 59 (91%) of the strains were identified as type b and the remainder as either type a (two strains) or non-typable (four strains). Of the 59 type b strains, 45 (76%) belonged to a single OMP subtype (equivalent to subtype 3L in the Barenkamp scheme); the remaining type b strains belonged to five other OMP subtypes. No correlation was apparent between OMP subtype and geographical region, clinical diagnosis or antimicrobial drug susceptibility pattern. Immunoblot subtyping enabled nine (18%) of 41 strains belonging to the principal OMP subtype to be distinguished from the remainder.