Internal Medicine

0521779407-09 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:12

Haemophilus Infections 651

Haemophilus Infections...............................

RICHARD A. JACOBS, MD, PhD

history & physical

History

■Haemophilus spp. are fastidious (require hemin or NADPH for aer-

obic growth) Gram-negative coccobacilli that grow in both aerobic

and anaerobic conditions.

■Presence of a polysaccharide capsule is virulence factor responsible

for the invasive disease of H influenzae type B (Hib); strains without

polysaccharide capsule are nontypable and usually associated with

local disease

■Humans are only known host and are colonized in the nasopharynx;

75% colonized with nontypable strains; less than 5% colonized with

Hib; spread is by droplets or direct contact with secretions

■In addition to nontypable H influenzae and Hib, other less com-

mon human pathogens include H parainfluenzae, H aphrophilus,

H paraphrophilus and H ducreyi (see sexually transmitted diseases

and chancroid)

Signs & Symptoms

■Hib causes meningitis (fever, headache, mental status changes,

nuchal rigidity indistinguishable from other causes of bacterial

meningitis), epiglottitis (sore throat, fever, dysphagia, dyspnea, dif-

ficulty handling secretions), pneumonia (fever, chills, productive

cough similar to other causes of bacterial pneumonia), bacteremia

with metastatic seeding (arthritis, pericarditis, endocarditis)

■Infections with nontypable strains cause sinusitis, otitis media, acute

exacerbations of chronic bronchitis, conjunctivitis and community

acquired pneumonia in the adult

■Haemophilus spp other than H influenzae produce disease similar

to nontypable H influenzae; also cause about 5% of cases of endo-

carditis

tests

■Diagnosis confirmed by positive culture of normally sterile body fluid

(blood, cerebral spinal fluid, pleural fluid); confirming infection with

nontypable strains (sinusitis, bronchitis, pneumonia) difficult since

these organisms are part of normal flora