Negative cultures of cerebrospinal fluid in partially treated bacterial meningitis.

Admission cerebrospinal fluid and serum were examined for antimicrobial activity in 296 Egyptian patients hospitalized with signs of meningitis. Assays were positive in 92%; 60% had large levels of antimicrobial activity in cerebrospinal fluid. Bacterial meningitis was diagnosed in 102 patients. The negative cerebrospinal fluid cultures in 58 of these patients were in part due to the antimicrobial activity in the cerebrospinal fluid. Mortality in patients with bacterial meningitis was greatest when cultures were positive and moderate levels of antimicrobial activity were present in the cerebrospinal fluid. Survival in these patients appeared to be enhanced if their prehospitalization antimicrobial use suppressed bacterial growth in the cerebrospinal fluid.