Effect of prior antibiotic therapy on concentrations of bacteria in CSF
W. E. Feldman
A prospective study was done to determine the effect of prior antibiotic
therapy on concentrations of bacteria in CSF at the time of diagnosis.
Concentrations of Haemophilus influenzae type b in CSF of partially treated
patients were significantly smaller than in CSF of untreated patients. This
was also true of patients with meningococcal meningitis, but no difference
was observed between patients with pneumococcal meningitis. The
identification of H influenzae by Gram stain of CSF was significantly
decreased by prior antibiotic therapy. Measurable levels of antibiotic
(penicillins, aminoglycosides) were present in CSF of ten of 23 patients.
Two partially treated patients were diagnosed by detection of meningococcal
antigen in CSF by counterimmunoelectrophoresis although cultures of CSF
were sterile. Both of these patients had measurable levels of penicillin in
CSF. These data indicate that prior antibiotic therapy significantly
decreases the concentration of H influenzae type b and meningococcus in CSF
and therefore decreases the usefulness of CSF Gram stain. Partial therapy
may sterilize the CSF of some patients.
