Development of a ribotyping scheme for Haemophilus influenzae type b

Ribotyping and outer-membrane protein subtyping were used to characterise 283 consecutive isolates of Haemophilus influenzae type b. These isolates were obtained primarily from patients with invasive disease in the UK and were received by the Public Health Laboratory Service Haemophilus Reference Laboratory prior to the implementation of Haemophilus influenzae serotype b vaccine in the UK. A subtyping scheme using the ribotyping method is suggested. Twenty-two ribotypes are described, 14 of which were found amongst the 283 clinical isolates characterised in this study. In contrast, only four outer-membrane protein subtypes were found amongst the 283 isolates. The ribotyping profiles were further used to estimate the relatedness of isolates. The resulting dendrogram suggested a population genetic structure different from that previously described for Haemophilus influenzae type b using multi-locus enzyme electrophoresis. This study shows the value of ribotyping as a subtyping method for epidemiological studies of Haemophilus influenzae type b. However, the further use of ribotyping for population genetic structure analysis of Haemophilus influenzae type b may be misleading and therefore inappropriate.