Once the Gram stain results become available, and the broad type of bacterial cause is known, it may be possible to change the antibiotics to those likely to deal with the presumed group of pathogens. The results of the CSF culture generally take longer to become available (24–48 hours). Once they do, empiric therapy may be switched to specific antibiotic therapy targeted to the specific causative organism and its sensitivities to antibiotics. For an antibiotic to be effective in meningitis it must not only be active against the pathogenic bacterium but also reach the meninges in adequate quantities; some antibiotics have inadequate penetrance and therefore have little use in meningitis. Most of the antibiotics used in meningitis have not been tested directly on people with meningitis in clinical trials. Rather, the relevant knowledge has mostly derived from laboratory studies in rabbits. Tuberculous meningitis requires prolonged treatment with antibiotics. While tuberculosis of the lungs is typically treated for six months, those with tuberculous meningitis are typically treated for a year or longer. Fluid Therapy
Fluid given intravenously are an essential part of treatment of bacterial meningitis. There is no difference in terms of mortality or acute severe neurological complications in children given a maintenance regimen over restricted-fluid regimen, but evidence is in favor of the maintenance regimen in terms of  emergence of chronic severe neurological complications.
Approximately 59% of recurrent meningitis cases are due to such anatomical abnormalities, 36% are due to immune deficiencies (such as complement deficiency, which predisposes especially to recurrent meningococcal meningitis), and 5% are due to ongoing infections in areas adjacent to the meninges. Viral
Viruses that cause meningitis include enteroviruses, herpes simplex virus (generally type 2, which produces most genital sores; less commonly type 1), varicella zoster virus (known for causing chickenpox and shingles), mumps virus, HIV, LCMV, Arboviruses (acquired from a mosquito or other insect), and the Influenza virus. Mollarets meningitis is a chronic recurrent form of herpes meningitis; it is thought to be caused by herpes simplex virus type 2. Fungal
There are a number of risk factors for fungal meningitis, including the use of immunosuppressants (such as after organ transplantation), HIV/AIDS, and the loss of immunity associated with aging. It is uncommon in those with a normal immune system but has occurred with medication contamination. Symptom onset is typically more gradual, with headaches and fever being present for at least a couple of weeks before diagnosis. The most common fungal meningitis is cryptococcal meningitis due to Cryptococcus neoformans. In Africa, cryptococcal meningitis is now the most common cause of meningitis in multiple studies, and it accounts for 20–25% of AIDS-related deaths in Africa. Other less common fungal pathogens which can cause meningitis include: Coccidioides immitis,  Histoplasma capsulatum, Blastomyces dermatitidis, and Candida species. Parasitic
A parasitic cause is often assumed when there is a predominance of eosinophils (a type of white blood cell) in the CSF.