Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Small gram-negative rod with a polysaccharide capsule.

Serologic typing is based on antigenicity of capsular polysaccharide.

Type b cause severe invasive disease.

Growth requires:

- heme (factor X)

- NAD (factor V)

Infects only humans; no animal reservoir.

Enters the body through upper respiratory tract, resulting in either asymptomatic colonization or infections – otitis media, sinusitis, pneumonia.

Organism produces an IgA protease that degrades secretory IgA, facilitating attachment to respiratory mucosa.

Enter bloodstream and spread to meninges.

Most infections occur in children between ages of 6 months and 6 years.

Haemophilus ducreyi:

- causes chancroid – painful genital ulcer(s) & enlarged lymph nodes.

- anaerobic secondary infection of lesions lead to gangrene & extensive destruction of genitalia.

- sexually transmitted.

- treatment: azithromycin or ceftriazone.

Disease:

- meningitis in young children.

- upper respiratory tract infections: otitis media, sinusitis & epiglottis, and sepsis in children.

- pneumonia in adults with chronic obstructive lung disease.

Rapid onset of fever, headache & stiff neck with drowsiness.

Sinusitis & otitis media:

- pain in affected area.

- opacification of infected sinus.

- redness with bulging of tympanic membrane.

Acute epiglottis:

- epiglottis becomes swollen & inflamed.

- child has difficulty breathing.

Haemophilus species are found in upper respiratory tract flora; occasionally caused bacterial endocarditis.

Isolation of organism on chocolate agar enriched with 2 growth factors.

An organism that presumes to grow in presence of both growth factors is H.influenzae.

Fluorescent-antibody stain.

Counterimmunoelectrophoresis

Latex agglutination tests detects capsular polysaccharide.

Taking a throat swab or using a tongue depressor can cause acute respiratory obstruction.

Drug of choice: ceftriaxone.

Important to give antibiotic treatment promptly due to high incidence of neurologic sequalae.

Otitis media & sinusitis treated with:

- ampicillin

- trimethoprim-sulfamethoxazole

Vaccine: capsular polysaccharide of type b conjugated to diphtheria toxoid.

Prevention: meningitis in close contacts of patients can be prevented by rifampin which decreases respiratory carriage.