Mixed bacterial meningitis.

Two recent cases of mixed bacterial meningitis at the Kansas City Veterans Administration Medical Center were studied. A review of the literature suggests that 1% of all cases of meningitis are caused by more than one bacterial species. Before 1950 such cases occurred predominantly in children and were caused by combinations of bacteria commonly associated with meningitis. Since 1950 a largely adult population has been affected by mixed bacterial meningitis, with a higher incidence of gram-negative bacillary organisms cultured from the cerebrospinal fluid. Common predisposing factors in this older group of patients include infection at contiguous foci, tumors in close proximity to the central nervous system, or fistulous communications with the central nervous system. Mortality was 26% for cases occurring before 1950 and 63% for those occurring after 1950. Failure to recognize one of the organisms present in the cerebrospinal fluid may result in the initiation of inadequate therapy in as many as 67% of cases. Empiric broad-spectrum antimicrobial therapy is indicated in symptomatic patients predisposed to mixed bacterial meningitis until culture results become available.