The type of bacterial meningitis that becomes epidemic among adults is caused by
Bacterial meningitis is caused by any one of several bacteria. The most common bacteria causing meningitis in children and adults in the U.S. are Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus) and, in older patients with decreased immunity, Listeria monocytogenes.eningitis is almost always caused by a bacterial or viral infection that began elsewhere in the body, such as in the ears, sinuses, or upper respiratory tract. Less common causes of meningitis include fungal infection, autoimmune disorders, and medications.