Correlates of high grade and low grade Haemophilus influenzae bacteremia

Routine use of the Isolator 1.5 Microbial Tube lysis direct plating blood culture system at our institution since November, 1983, provided a unique opportunity to study bacteremia in children from a quantitative perspective. In a 3-year period, 90 episodes of Haemophilus influenzae bacteremia occurred in immunocompetent outpatients; 83 of these met the criteria for study. Patients with high grade bacteremia (greater than 100 colony-forming units/ml) were more likely to have meningitis than those with low grade bacteremia (less than or equal to 100 colony-forming units/ml); conversely low grade bacteremia patients were more likely to have cellulitis or arthritis. Of 38 meningitis patients those with high grade bacteremia (n = 25) had a significantly shorter duration of illness before presentation than those with low grade bacteremia (median, 1 vs. 3 days; P less than or equal to 0.006). In addition high grade bacteremia patients had significantly lower white blood cell counts (median, 11.4 vs. 17.3 X 10(3)/mm3; P less than or equal to 0.007) and absolute neutrophil counts (5.5 vs. 11.1 X 10(3)/mm3; P less than or equal to 0.01). Only 1 of 8 meningitis patients who were pretreated with appropriate antibiotics had high colony counts compared to 7 of 8 matched controls (P = 0.04).