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Aspects of the pathogenicity of some oral and other haemophili
Abstract:
The pathogenicity of the predominantly non-capsulated, V-factor requiring haemophili that are commonly recovered from oral infections has been explored by studies of their endotoxins and infectivity as compared with those of Haemophilus influenzae. Similar yields of endotoxin (2.40-2.59% w/w) were obtained from all the haemophili examined except H. haemolyticus (1.61% w/w). The lipopolysaccharide (LPS) extracts all contained heptoses but not 2-keto-3-deoxyoctonate (KDO). The fatty acid compositions of the lipid-A fractions were essentially similar but comprised 76% of the LPS in the H. influenzae type d strain tested and only 20% in the H. influenzae type b strain and some strains of H. parainfluenzae. All extracts contained arachidic acid, which may be unique to haemophili. The endotoxins from all strains produced characteristic pyrogenic and polymorph effects in rabbits. The endotoxins from the pharyngeal X- and V-factor-requiring strains had LD50 values for actinomycin-D-sensitised mice of 2.4-2.7 micrograms/kg, and were about eight times more potent than those from the oral V-factor-requiring strains (LD50 values 17.2-22.4 micrograms/ml). Approximately ten thousand times more free endotoxin was detected in broth cultures of H. influenzae type b than in those of oral haemophili, and this greater endotoxin release was not associated with a greater degree of autolysis. Endotoxin release from viable cells may be important in the pathogenicity of this organism. H. influenzae type b was much more potent in producing infection in chambers implanted subcutaneously in guinea pigs than were oral strains of haemophili; only 10 type b organisms were required, compared with 9 X 10(5) of H. parainfluenzae. However, in infections maintained for 90 days, the numbers of haemophili--c. 10(7)/ml of chamber fluid--were similar for all the test strains. Thus, although the oral haemophili lack special attributes of invasiveness and resistance to host defences, they are not devoid of pathogenic potential and, if allowed to proliferate, may become an important element in an infection.
Insights
Oral Haemophili strains, commonly found in oral infections, exhibit pathogenic potential despite lacking invasiveness. Their endotoxins are less potent than Haemophilus influenzae type b, but proliferation can lead to significant infection.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Haemophili, particularly non-capsulated strains requiring V-factor, are frequently isolated from oral infections.
- Understanding their pathogenicity is crucial for distinguishing them from more virulent species like Haemophilus influenzae.
Purpose of the Study:
- To compare the endotoxins and infectivity of oral Haemophili strains with Haemophilus influenzae.
- To elucidate the pathogenic potential of commonly encountered oral Haemophili.
Main Methods:
- Extraction and analysis of endotoxins (lipopolysaccharides) from various Haemophili strains.
- Assessment of endotoxin potency using LD50 values in actinomycin-D-sensitized mice.
- Evaluation of infectivity in guinea pig subcutaneous chambers, comparing oral Haemophili with H. influenzae type b.
Main Results:
- Similar endotoxin yields were observed across most strains, with variations in lipid-A content and the presence of arachidic acid.
- Endotoxins from all strains induced pyrogenic and polymorph effects in rabbits.
- H. influenzae type b exhibited significantly higher endotoxin release and infectivity in vivo compared to oral Haemophili strains.
Conclusions:
- Oral Haemophili strains possess pathogenic potential, though less pronounced than H. influenzae type b.
- Endotoxin release from viable cells may contribute to pathogenicity.
- Proliferation of oral Haemophili can lead to significant infections, highlighting their clinical relevance.