Neutrophilic bacterial meningitis: pathology and etiologic diagnosis of fatal cases

The frequency of fatalities due to acute bacterial meningitis has decreased significantly due to vaccinations, early diagnoses, and treatments. We studied brain tissues of patients with fatal neutrophilic meningitis referred to the Centers for Disease Control for etiologic diagnosis from 2000-2009 to highlight aspects of the disease that may be preventable or treatable. Demographic, clinical, and laboratory data were extracted from records. Of 117 cases in the database with a diagnosis of meningitis or meningoencephalitis, 39 had neutrophilic inflammation in the meninges. Inflammatory cells infiltrated the superficial cortex in 16 of 39 (41%) cases. Bacteria were found using Gram and bacterial silver stains in 72% of cases, immunohistochemistry in 69% (including two cases where the meningococcus was found outside the meninges), and PCR in 74%. Streptococcus pneumoniae was the cause of the meningitis in 14 patients and Neisseria meningitidis in 9. In addition, Streptococcus spp. were found to be the cause in six cases, while Staphylococcus aureus, Staphylococcus spp., Enterococcus spp., and Fusobacterium were the cause of one case each. There were six cases in which no specific etiological agent could be determined. The mean age of the patients with S. pneumoniae was 39 years (range 0-65), with N. meningitidis was 19 years (range 7-51), whereas that for all others was 31 years (range 0-68). In summary, our study shows that S. pneumoniae continues to be the most frequent cause of fatal neutrophilic bacterial meningitis followed by N. meningitidis, both vaccine preventable diseases.