Relative proportions ofHaemophilus species in the throat of healthy children and adults

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Abstract
To determine normal proportions of pharyngealHaemophilus species, qualitative and quantitative mapping of the species in the pharynx of ten healthy children and ten healthy adults was carried out using a selective and a non-selective medium.Haemophilus organisms were present in all samples, comprising approximately 10 % of the total cultivable flora (range 0.6–36.9 %).Haemophilus parainfluenzae was a member of the normal flora throughout life, constituting 74% of pharyngealHaemophilus organisms.Haemophilus segnis andHaemophilus paraphrophilus occurred more frequently in samples from adults, whereasHaemophilus haemolyticus was present in only one sample. Non-encapsulatedHaemophilus influenzae strains, usually of multiple biotypes, were present in 80% of the children but accounted for a mean of only 1.8 % of the total flora. Their number decreased with increasing age; 40 % of the adults harboredHaemophilus influenzae but only of a single biotype which constituted a minor proportion of the total flora (mean 0.15%). These findings suggest that host mechanisms can influence changes in the proportions ofHaemophilus influenzae strains colonizing the host.

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