H. influenzae is a fastidious, gram-negative, pleomorphic coccobacillus that requires factor X (hematin) and factor V (phosphopyridine nucleotide) for growth. Some H. influenzae isolates are surrounded by a polysaccharide capsule and can be serotyped into 6 antigenically and biochemically distinct types designated by letters a–f.
In the prevaccine era, meningitis accounted for more than half of invasive H influenzae disease. Clinically, meningitis caused by H. influenzae type b cannot be differentiated from Neisseria meningitidis or Streptococcus pneumoniae.
It may be complicated by other foci of infection such as the lungs, joints, bones, or pericardium.
Antimicrobial therapy should be administered intravenously for 7–14 days for uncomplicated cases. Cefotaxime, ceftriaxone, and ampicillin cross the blood-brain barrier during acute inflammation in adequate concentrations to treat H. influenzae meningitis. Intramuscular therapy with ceftriaxone is an alternative in patients with normal organ perfusion.
The prognosis of H. influenzae type b meningitis depends on the age at presentation, duration of illness before appropriate antimicrobial therapy, cerebrospinal fluid (CSF) capsular polysaccharide concentration, and rapidity with which it is cleared from CSF, blood, and urine. Clinically manifested Continue reading »
