To further define the clinical features and natural history of unsuspected Haemophilus influenzae type b (Hib)
bacteremia, we retrospectively reviewed the records of 322
Hib infections observed during a 45-month period at Children's Hospital, Boston. We identified 31 patients with unsuspected Hib
bacteremia and 19 with unsuspected Hib antigenemia and sterile blood cultures. Bacteremic patients were typically under two years of age (81%), had high
fevers (mean = 39.5 degrees C), and frequently had
otitis media (65%) diagnosed as their only focus of
infection at presentation. Nineteen of 31 were empirically treated with oral
antibiotics. Ten of 31 (32%) developed focal infectious complications consisting of
meningitis (n = 7),
cellulitis (n = 2), and
pneumonia (n = 1). Children with focal infectious complications differed from those without infectious complications in having a significantly higher mean
fever of 40.3 degrees C compared to 39.7 degrees C (P less than 0.05). Five of 19 (26%) empirically treated patients developed focal complications (all
meningitis) compared to five of 12 (42%) untreated patients. Blood cultures at follow-up visit were positive in three of 19 (9%) treated patients and seven of 12 (42%) untreated patients (P less than 0.05). Of the 19 children with antigenemia and sterile blood cultures, 16 (84%) were empirically treated with
antibiotics, and none had positive blood cultures or
focal infections on follow-up evaluation. Children with occult Hib
bacteremia are at high risk for developing serious
focal infections, particularly
meningitis, despite empiric
antibiotic therapy. Once Hib
bacteremia is suspected, strong consideration should be given to parenteral in hospital
antibiotic therapy. The utility of rapid
antigen detection for identifying high-risk patients requires further evaluation.