Infectious etiology of Meningitis

Common bacteria that cause meningitis in adults includes: Streptococcus pneumoniae, Neisseria meningitidis, Lysteria monocytogenes, Haemophilus influenzae, Staphylococcus spp. (aureus and epidermidis, especially in postoperative patients or patients with VP shunts), Gram-negative organisms (Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae), etc.
The most common viral etiology of meningitis is enterovirus (Echo, Coxachie), but also is important to mention other such as Herpes simplex, Varicella (including zoster), adenovirus, HIV, etc.
Fungal infections affecting the CNS are not uncommon. The most frequently involved organisms are: Cryptococcus neoformans (especially in immunosupressed patients such as AIDS), Histoplasma capsulatum, Coccidioides immitis, Candida spp., etc.
Other infectious agents able to caused meningitis includes: Mycobacterium tuberculosis, atypical mycobacteria, Brucella spp., Angyostrongylus cantonensis, Acanthamoeba spp., etc.