To further confirm that rats had cellular changes in the brain consistent with bacterial meningitis, rat brain slices from one rat with a median neurological score and from one saline control rat were stained for MPO, a neutrophil marker, and Iba-1, a macrophage/microglia marker (Fig. 2a), and a section of the meninges was imaged. The gene discussed is MPO; the disease is bacterial meningitis.