Quantitation of bacteria in cerebrospinal fluid and blood of children with meningitis and its diagnostic significance

Cerebrospinal fluid (CSF) specimens from pediatric patients with meningitis were examined for their concentration of microbes and the relationship of this count to the bacteremia levels, microscopy results, and polymorphonuclear leukocyte concentration. A total of 2,031 consecutive CSF specimens were analyzed, of which 63 (3.1%) were positive by culture from the same number of patients. We observed that 85% of the total CSF specimens positive for Haemophilus influenzae type b, Streptococcus agalactiae, Streptococcus pneumoniae, and Neisseria meningitidis had counts in excess of 10(3) CFU/ml, with 56% of the specimens exceeding 10(5) CFU/ml. A correlation existed between the number of organisms present in the CSF and blood. For example, from a total of 22 patients who had counts of H. influenzae greater than 10(3) CFU/ml in the CSF, 16 or 73% had levels of bacteremia greater than 10(3) CFU/ml. It was also noted that the bacterial concentration had a profound effect on the sensitivity of microscopy. The percentage of positive results increased from 25% with less than or equal to 10(3) CFU/ml to 60% in the range of greater than 10(3) to 10(5) CFU/ml and to 97% at concentrations of greater than 10(5) CFU/ml. Furthermore, a significant correlation (P less than 0.01) was noted between the concentration of bacteria in the CSF and the number of polymorphonuclear leukocytes observed on microscopy.