Outer membrane protein and biotype analysis of non-serotypable strains of Haemophilus influenzae.

Strains of Haemophilus influenzae (n = 161) were isolated from inpatients with symptoms of pulmonary infection. Conventional tests showed that 144 strains were non-serotypable and all belonged to one of eight biotypes. The common biotypes were 2 (41%), 3 (27.1%), 1 (13.2%) and 5 (10.4%). The outer membrane protein (OMP) profiles of 59 non-serotypable strains were examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A comparison of OMP profiles suggested a possible association between several strains belonging to biotype 2. Although no clear correlation was established between biotype or OMP profile cluster groups and the age or clinical state of the patients from whom the strains were isolated, SDS-PAGE analysis was a useful technique for the epidemiological study of non-serotypable H influenzae.