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[Haemophilus influenzae: colonization and infection]
1Unité de pathologie infectieuse pédiatrique, centre de pédiatrie Gatien-de-Clocheville, Tours, France.
Abstract:
Haemophilus influenzae can be demonstrated as a saprophyte in more than two-thirds of children, and almost as frequently in adults. Noncapsulated strains are more frequent than capsulated type b strains which are found in 5% of the samples. Other capsulated strains are rare. Transmission is made easier with close contact (daycare nurseries, home). Colonization is the result of adherence to nasopharyngeal epithelial cells, although characterized adhesion factors cannot be demonstrated for all strains (pili, adhesins, secretory IgA1 protease). Systemic infection is the result of the invasion of pharyngeal epithelium, made easier by upper respiratory tract infection. There is a risk of meningitis for high level bacteremia (> or = 10(5) CFU/ml). Risk factors are: age (child < 5 years), alteration of reticuloendothelial system, agammaglobulinemia. Anti-Haemophilus type b vaccine prevents nearly all infections, and suppresses or sharply reduces colonization.
Insights
Haemophilus influenzae is common in children and adults, with non-encapsulated strains being most frequent. Vaccination against Haemophilus influenzae type b significantly reduces infections and colonization.
Area of Science:
- Microbiology
- Infectious Diseases
- Vaccinology
Background:
- Haemophilus influenzae is a common bacterium found in the nasopharynx of children and adults.
- Non-encapsulated strains are more prevalent than encapsulated strains, particularly type b.
- Transmission occurs through close contact, with colonization facilitated by adherence to respiratory epithelial cells.
Purpose of the Study:
- To investigate the prevalence and transmission of Haemophilus influenzae.
- To identify risk factors for systemic infections, including meningitis.
- To evaluate the impact of anti-Haemophilus influenzae type b vaccination.
Main Methods:
- Bacteriological sampling and analysis of nasopharyngeal specimens.
- Identification of encapsulated and non-encapsulated strains.
- Review of clinical data and vaccination status.
Main Results:
- Haemophilus influenzae detected in over two-thirds of children and frequently in adults.
- Non-encapsulated strains predominated; encapsulated type b strains found in 5% of samples.
- High bacteremia levels (> or = 10(5) CFU/ml) increase meningitis risk, especially in children under 5, immunocompromised individuals, and those with agammaglobulinemia.
Conclusions:
- Haemophilus influenzae colonization is widespread, with varied strain prevalence.
- Vaccination against Haemophilus influenzae type b is highly effective in preventing infections and reducing colonization.