The pathogenicity of Haemophilus influenzae

Abstract

Problems about the pathogenicity of an organism can be classified as: (1) clinical and epidemiological-what diseases does it cause or take part in, and when? (2) research (with prophylactic and therapeutic implications)-how does it do so? Category (1) answers for Haemophilus injuenzae began in 1892, with Pfeiffer's claim that it was the cause of influenza; but the true picture of the range of pathogenic activities of this species became clear in the period 1930-1960 answers have in general been more recent, and are still far from complete (as is the case with most pathogens); but a fascinating array of contributions has appeared in the past few years. What and when?To discuss the pathogenicity of H . injuenzae as though the species were in this respect a single entity would be to confuse things that differ widely. It has been clear for over 50 years (Pittman, 1931), but not known as widely as it should have been, that a minority of H. injluenzae strains have polysaccharide capsules, and that one of the six capsular types (type b) differs in pathogenicity from the rest of the species at least as markedly as do streptococci of Lancefield's group A from other P-haemolytic streptococci. The main facts about the distribution and pathogenicity of capsulated and non-capsulated strains of H. injluenzae are summarised in the table. The species has 00 non-human hosts. Capsular type bThe 2 4 % carriage rates for H. injluenzae type b listed in the table represent the findings of numerous surveys, each of which was a "snapshot" of the distribution of the organism in one community at one time. These give no information about the dynamics of carriage. Rates in the range 2 4 % would be found, for example, in a community of which each member carried the organism for about 2 months during a 5-year period. There is some evidence (e.g., Turk, 1963) that the duration of carriage of H. injluenzae type b by individual children is often of that order. Moreover, when Sell, Turner and Federspiel(l973) studied 55 children through their first 5 years of life, culturing nasopharyngeal swabs mostly at 3-month intervals, they isolated H.

Otitis Media in Greenland: studies on historical, epidemiological, microbiological, and immunological aspects

“…Hib was found very frequently in AOM, control and healthy children compared with 2%-4% Hib carriage rates in healthy persons as reported in the review by Turk (1984) and 1.3% in Chinese and Vietnamese children in Hong Kong (Sung et al 1995). Hib vaccination was not initiated at the time of the present study in Greenland.…”

Bacterial-induced release of inflammatory mediators by bronchial epithelial cells

“…In contrast, studies of septicaemia, pneumonia and systemic H. influenzae infections in children have suggested that these are the most common clinical manifestations of H. influenzae type b [2,3].…”

Structural Determinants of the Interaction between the TpsA and TpsB Proteins in the Haemophilus influenzae HMW1 Two-Partner Secretion System

“…Haemophilus influenzae is a human-specific pathogen that is a common cause of localized respiratory tract disease and initiates infection by colonizing the respiratory epithelium in the nasopharynx (14,15). Approximately 75% to 80% of isolates express homologous high-molecular-weight proteins called HMW1 and HMW2 that mediate highlevel adherence to respiratory epithelial cells and presumably facilitate the process of colonization (16,17).…”