• Meningitis is the infection of the meninges and subarachnoid space that is usually caused by bacteria results in high mortality and morbidity throughout the world

• H influenza type B, N meningitidis and S pneumoniae 
• Causative agents depend on the age of the patient and predisposing factors
• The introduction of conjugated vaccines have caused decline in the incidence of bacterial meningitis in children thus majority of cases are now present in the adult population

Other causes of acute meningitis include the following:

• Spirochetes eg Treponema pallidum
• Mycobacteria eg Mycobacterium tuberculosis
• Fungi eg Cryptococcus, Coccidioides, Sporothrix
• Viruses eg herpes simplex virus (HSV), varicella zoster, cytomegalovirus (CMV), enterovirus
• Protozoa and helminths

• Classic triad: Fever, neck stiffness and an altered level of consciousness
• Other symptoms:
  
  • Chills
  • Myalgia
  • Photophobia
  • Severe headache
  • Focal neurologic symptoms (eg cranial nerve palsies, ataxia, dilated/unequal and poorly reacting pupils - late sign)
  • Nausea/vomiting
  • Seizures (late sign)
  • Some patients may present with petechial rash
  • Some patients may not present with the classic signs (eg alcoholics, patients who are immunocompromised and who had meningitis after neurosurgery)