Bacterial Infections

Acute Bacterial Meningitis

• Streptococcus pneumoniae
• Neisseria meningitidis
• Haemophilus influenzae type b
• Group B Streptococcus (neonates)
• Escherichia coli (neonates)
• Listeria monocytogenes

Brain Abscess

• Streptococcus species (e.g., Streptococcus milleri)
• Staphylococcus aureus
• Anaerobes (e.g., Bacteroides, Fusobacterium)
• Mycobacterium tuberculosis

Tuberculous Meningitis

• Mycobacterium tuberculosis

Neuroborreliosis

• Borrelia burgdorferi (Lyme disease)

Neurosyphilis

• Treponema pallidum

Listeriosis

• Listeria monocytogenes

Other Bacterial Infections

• Rickettsia species (Rocky Mountain spotted fever)
• Brucella species (Brucellosis)
• Bartonella henselae (Cat scratch disease with CNS involvement)

Viral Infections

Viral Meningitis

• Enteroviruses (e.g., Coxsackievirus, Echovirus)
• Mumps virus
• Herpes simplex virus type 2 (HSV-2)

Viral Encephalitis

• Herpes simplex virus type 1 (HSV-1)
• Varicella-zoster virus (VZV)
• Epstein-Barr virus (EBV)
• Cytomegalovirus (CMV)
• Enteroviruses
• Arboviruses (e.g., West Nile virus, Japanese encephalitis virus, Zika virus)
• Rabies virus

Congenital Viral Infections

• Cytomegalovirus (CMV)
• Rubella virus
• Zika virus
• Herpes simplex virus (neonatal HSV)

Progressive Viral Infections

• Subacute sclerosing panencephalitis (SSPE) – Measles virus
• Progressive multifocal leukoencephalopathy (PML) – JC virus

Fungal Infections

Chronic Meningitis

• Cryptococcus neoformans
• Coccidioides immitis
• Histoplasma capsulatum

Brain Abscess

• Candida species
• Aspergillus species
• Zygomycetes (e.g., Rhizopus, Mucor)

Other Fungal Infections

• Blastomyces dermatitidis
• Sporothrix schenckii

Parasitic Infections

Protozoal Infections

• Toxoplasma gondii (toxoplasmosis)
• Plasmodium falciparum (cerebral malaria)
• Naegleria fowleri (primary amoebic meningoencephalitis)
• Acanthamoeba species (granulomatous amoebic encephalitis)

Helminthic Infections

• Taenia solium (neurocysticercosis)
• Schistosoma species
• Echinococcus species (hydatid disease)
• Angiostrongylus cantonensis (eosinophilic meningitis)

Prion Diseases

• Creutzfeldt-Jakob disease (CJD)
• Fatal familial insomnia
• Gerstmann-Sträussler-Scheinker syndrome
• Kuru

Mixed or Undetermined Etiology

• Post-infectious encephalitis (e.g., acute disseminated encephalomyelitis, ADEM)
• Infectious-triggered autoimmune encephalitis (e.g., anti-NMDAR encephalitis following viral infections)