<P> Recent skull trauma potentially allows nasal cavity bacteria to enter the meningeal space . Similarly, devices in the brain and meninges, such as cerebral shunts, extraventricular drains or Ommaya reservoirs, carry an increased risk of meningitis . In these cases, the persons are more likely to be infected with Staphylococci, Pseudomonas, and other Gram - negative bacteria . These pathogens are also associated with meningitis in people with an impaired immune system . An infection in the head and neck area, such as otitis media or mastoiditis, can lead to meningitis in a small proportion of people . Recipients of cochlear implants for hearing loss are more at risk for pneumococcal meningitis . </P> <P> Tuberculous meningitis, which is meningitis caused by Mycobacterium tuberculosis, is more common in people from countries in which tuberculosis is endemic, but is also encountered in persons with immune problems, such as AIDS . </P> <P> Recurrent bacterial meningitis may be caused by persisting anatomical defects, either congenital or acquired, or by disorders of the immune system . Anatomical defects allow continuity between the external environment and the nervous system . The most common cause of recurrent meningitis is a skull fracture, particularly fractures that affect the base of the skull or extend towards the sinuses and petrous pyramids . 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 . </P> <P> 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, and LCMV . Mollaret's meningitis is a chronic recurrent form of herpes meningitis; it is thought to be caused by herpes simplex virus type 2 . </P>

Where does the bacteria that causes meningitis come from