Studies on Haemophilus influenzae
The population structure of non-typable Haemophilus influenzae was examined by SDS polyacrylamide gel electrophoresis of whole-cell polypeptide profiles. 223 clinical non-typable isolates were characterised. Clones were defined as having Dice similarity coefficients of over 95%. 23 multimember clones were identified, containing between 2 and 8 members. The remaining 66% of strains were regarded as unique. Isolates from children were less diverse than those from adults. Isolates within multimember clones were widely distributed temporally and geographically. Clones were also identified in a collection of 14 H.influenzae type b strains, but not in 22 H.parainfluenzae isolates. Further studies suggested that nosocomial transmission of non-typable H.influenzae was uncommon. Strains were further characterised by Western blotting, culture supernate profiles, outer membrane proteins, two dimensional gel electrophoresis, DNA restriction fragments (using BamHI) and rRNA probing of DNA restriction fragments. Analysis of restriction fragments, and rDNA fragments, defined clonal groups which were identical in membership to those defined by polypeptide analysis. Unique restriction fragment profiles and sixteen rDNA patterns were observed for isolates dissimilar by polypeptide analysis. IgG antibody directed against non-typable H.influenzae was studied by Western blotting. Marked differences in response of human sera from different individuals were observed to antigens of non-typable isolates. Comparison of paired sera samples taken ten years apart from volunteers showed little change in antibody profiles against H.influenzae. Immunoblot analyses of sera from smokers were also performed. Applications of rapid typing methods to clinical problems are discussed.