Hemophilis and others

Hemophilus influenzae:
Important properties:
• Small Gram-negative rods.
• It may encapsulated or uncapsulated.
• It is non motile.
• Aerobic organism.

Antigenic structure and virulence factors:
• Capsule is polysaccharides. Encapsulated strains divided into six serotypes (a,b,c,d,e,f). H.influenzae type-b(HIB) is most common pathogen for human.
• It produces endotoxin, no exotoxin
• IgA protease.
• Pili : they act as attachment factors.
Source and Transmissio:
• Humans are only natural host(obligate human pathogen) at URT.
• H.influenzae is transmitted from person to person by respiratory droplets.
Pathogenesis:
• The organism enters the body from primary site in URT. It produces IgA protease that degrades secretory IgA thus facilitating attachment to respiratory mucosa. The organism can enter bloodstream and disseminate to distant sites such as meninges.
• The pathogenesis involves antiphagocytic capsule and endotoxin. The capsulated strains are mostly responsible for meningitis, pneumonia and epiglottitis in children. Noncapsulated (untypeable) strains tend to cause pneumonia, otitis media, sinusitis and conjunctivitis in adults, especially elderly.
Diseases and clinical findings:
• Meningitis: H.influenzae-b(HIB) is most common cause of meningitis in children age 5 months to 5 years(especially infants, 6-12 months). After 5-6 days, serious seguelae and clinical features of meningitis include; fever, headach, and stiff neck with drowsiness. Hemophilus meningitis may associated with neurologic morbidity (serious sequelae); hearing loss, mental retardation, delayed language development and seizer.
• Pneumonia, laryngotrachitis, and epiglottitis develop in infants. C/F of pneumonia are cough, fever, headache, chest pain , sweating, shortness of breath.
• Sinusitis and otitis media cause pain in affected area, opacification of infected sinus, and redness with bulging of tympanic membrane. HIb and pneumococci are two of most common etiologic agents of otitis media and sinusitis.