title: Expression of capsules by Haemophilus influenzae in mixed infections.
abstract: The pathogenicity of eight clinical isolates of non-type b Haemophilus influenzae was investigated by inoculating them subcutaneously into mice, alone or mixed with viable or non-viable bacteria of certain other species. Three of the H. influenzae isolates were non-capsulated while five were slightly capsulated (less than 1% of organisms had capsules). The other strains of bacteria tested were four isolates of capsulated and four isolates of non-capsulated pigmented strains of Prevotella sp. and Porphyromonus sp. as well as a capsulate Klebsiella pneumoniae ("helpers"). None of the non-capsulated strains induced an abscess when inoculated alone. Following co-inoculation of viable or non-viable "helpers" with H. influenzae, abscesses were formed in all instances in which the "helper" had a capsule. Profusely capsulated cells of H. influenzae were recovered, however, only from abscesses induced with the five slightly capsulated strains of H. influenzae. These capsulated organisms were found serologically to be of type b and induced abscesses when inoculated alone. Our findings illustrate the ability of non-capsulated strains of H. influenzae to produce progeny of capsulated type b organisms after co-inoculation with certain other species.
authors.affiliation: Naval Medical Research Institute, Bethesda, Maryland, USA.
authors.forename: I
authors.initials: I
authors.lastname: Brook
authors.forename: J D
authors.initials: JD
authors.lastname: Gillmore
mesh_terms: D000038:Abscess / Q000382:microbiology*; D000818:Animals; D016667:Bacterial Capsules / Q000648:ultrastructure; D006192:Haemophilus Infections / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000145:classification / Q000472:pathogenicity* / Q000648:ultrastructure; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D013045:Species Specificity; D015163:Superinfection / Q000382:microbiology*