Characterization of Capsular Genes in Haemophilus influenzae Isolates from H. influenzae Type b Vaccine Recipients

• Published in: The Journal of infectious diseases 1995-04, Vol.171 (4), p.1075-1075
• Main Authors: Falla, T. J., Crook, D. W. M., Anderson, E. C., Ward, J. I., Santosham, M., Eskola, J., Moxon, E. R.
• Format: Article
• Language: English
• Subjects: Bacterial Capsules - genetics; Child; DNA probes; Epidemiology; Genes, Bacterial - genetics; Genetic loci; Genotype; Genotypes; Haemophilus; Haemophilus Infections - virology; Haemophilus influenzae; Haemophilus influenzae - classification; Haemophilus influenzae - genetics; Haemophilus influenzae - pathogenicity; Haemophilus Vaccines; Humans; Polysaccharides, Bacterial; Public health; Ribotyping; Vaccination; Virulence
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/171.4.1075

We analyzed 215 H. influenzae strains from vaccine trials. All isolates were obtained from controlled trials with Alaska Natives, residents of California (unpublished data), Navajo and Apache Indians, and Finnish children. All H. influenzae isolates from blood or CSF (or both) in vaccine recipients and a collection of such isolates from subjects who were not vaccinated, from the respective vaccine trial control populations, were examined. The capsular genotype patterns produced by NC, b super(-), and type b strains could be easily distinguished. The distribution of the capsular genotypic patterns of isolates from vaccinated and unvaccinated cases were compared for the three studies in which all isolates were characterized. The Finnish strains were excluded from statistical analysis, as control strains were an age-controlled collection of type b isolates representing a small selection and not all isolates were from vaccine control subjects. No difference in the distribution of cap b genotypes was found in Hib strains causing disease in Hib vaccine recipients compared with those from nonrecipients. Only 2 strains revealed a novel b capsulation locus and contained tandemly repeated and intact copies of cap b in contrast to the usual multicopy b locus, which contains one copy of cap b with a deletion of bexA and part of the adjacent copy of IS 1016. One strain with this novel genotype came from a nonvaccinated individual and the other from a vaccinee. Twenty-three isolates were nonserotypeable; 13 isolates were b super(-) (capsule-deficient type b) strains and 10 were NC strains. However, the proportion of b super(-) strains was not significantly different (Yates's corrected chi super(2)) between vaccinated and nonvaccinated groups. However, 57% of nonserotypeable H. influenzae were b super(-) strains. This was unexpectedly high and may have arisen subsequent to repeated passage. However, in that case, an equivalent proportion of isolates from vaccinated and nonvaccinated subjects would have been affected. Only 1 nontype b capsulate strain (type a) was observed, and it had a characteristic cap a genotype. No difference in the distribution of ribotype patterns between strains from vaccinated and nonvaccinated persons was revealed.