Haemophilus influenzae

Gram negative infection commonly involved with respiratory tract infections, otitis media, sinusitis, tracheobronchitis, and pneumonia.

Colonizes the human respiratory tract.

Pneumonia with these organisms common in patients with COPD.

Bacterium normally present in the upper respiratory tract and pharynx and to a lesser extent in the mucosa of the genital tract and conjunctiva.

Important cause of meningitis in children.

Uncommon cause of community-acquired pneumonia but a common cause of nosocomial pneumonia.

There are typeable and nontypeable varieties.

80% of healthy human population are carriers of nontypeable H influenzae.

Lack of a polysaccharide capsule distinguishes nontypeable H.influenzae from encapsulated serotypes types a-f.

Non-typable H .influenzae is classified into eight bio types.

Non–typeable H influenzae is frequently associated with noninvasive respiratory infections such as sinusitis, bronchitis, but severe invasive disease may occur.

Colonization of the female general tract can lead to obstetrical infections and neonatal sepsis.

Nontypeable H influenzae frequently colonizes the lower respiratory tract of patients with COPD and cystic fibrosis.

The most common clinical manifestations of infection with nontypeable H influenzae are otitis media and respiratory infections in adults with occasional bacteremia and an estimated 1.7 cases per 100,000 adults with invasive disease.

Invasive infection highest among elderly, alcoholics, patients with COPD and malignancy.

Infections by nontypeable H influenzae associated with invasive disease and significant mortality.

Types a, c, d, e, and f are associated with invasive disease.

Invasive infections associated with H influenzae include epiglottitis, septic arthritis, cellulitis, intra-abdominal infections, cholecystitis, osteomyelitis, pericardial infections, vascular graft infections and empyemas.

Type b vaccine improves duration of immunity, reduces nasopharyngeal carriage rate in children younger than 2 years.

Before development of Haemophilus influenza type b conjugate vaccines it was the most common cause of bacterial meningitis in children less than age 5 years.

Since the use of Haemophilus influenza type b vaccine immunizations in the early 1990’s the incidence of Haemophilus influenzae b declined from a peak of 41 cases per 100,000 children less than 5 years in 1987 to approximately 0.11 cases per 100,000 in 2007.

Since introduction of the H influenzae serotype b congugate vaccine into high income countries, non-typeable H influenzae has become the leading cause of invasive H influenzae disease for all ages.

Risk factors for invasive NTHi infection include extremes of age, COPD, malignancy, pregnancy, and HIV infection.

Among adults, bacteremic pneumonia, bacteremia without focus, and meningitis are the most commonly reported invasive NTHi clinical syndromes.

The acquisition of a carrier state is necessary for the development of invasive disease and vaccines reduce the asymptomatic carrier state and thereby reduce transmission of disease.

After the introduction of H influenzae type b immunization in children, invasive infections in unimmunized adults decreased, but the overall rate of invasive disease in adults increased by noncapsulated strains.

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