What are the differences between bacterial, viral, and fungal meningitis?

From the Guidelines

Bacterial meningitis is a medical emergency that requires immediate antibiotic therapy, typically with ceftriaxone (2g IV every 12 hours) plus vancomycin (15-20 mg/kg IV every 8-12 hours) as empiric treatment until culture results are available. Meningitis is an inflammation of the membranes (meninges) surrounding the brain and spinal cord, and requires prompt diagnosis and treatment based on the causative organism. The treatment approach varies depending on the type of meningitis: bacterial, viral, or fungal.

Diagnosis and Treatment

• Bacterial meningitis is a medical emergency that requires immediate antibiotic therapy, as stated above, with treatment duration typically 7-14 days depending on the pathogen identified 1.
• Viral meningitis is usually less severe and self-limiting, with treatment focused on supportive care including rest, fluids, and pain relievers. Antiviral medications like acyclovir (10 mg/kg IV every 8 hours) may be used if herpes virus is suspected 1.
• Fungal meningitis requires prolonged antifungal therapy, commonly with amphotericin B (0.7-1.0 mg/kg/day IV) followed by fluconazole (400-800 mg daily), often for weeks to months.

Prevention and Pathophysiology

• Patients with meningitis typically present with fever, headache, neck stiffness, and altered mental status. Diagnosis involves lumbar puncture to analyze cerebrospinal fluid for cell counts, glucose, protein, and to identify pathogens.
• Prevention includes vaccination against common bacterial causes (pneumococcal, meningococcal, and Hib vaccines) and practicing good hygiene 1.
• The different treatment approaches reflect the varying pathophysiology of each type: bacterial meningitis causes rapid, severe inflammation requiring immediate antimicrobial intervention; viral causes typically trigger a milder immune response; while fungal infections develop more slowly but require extended treatment due to the organisms' persistence.

Key Considerations

• Clinicians' judgement should continue to be used to estimate the risk of bacterial meningitis and whether empiric antibiotic and adjunctive therapy needs to be initiated 1.
• Molecular diagnosis, such as PCR testing of CSF, can aid in the diagnosis of viral meningitis, particularly for enteroviruses, herpes simplex viruses, and varicella zoster virus 1.

From the Research

Types of Meningitis

• Bacterial meningitis: a serious neurologic illness with significant morbidity and mortality if not recognized and treated promptly and appropriately 2
• Viral meningitis: physical examination may not perform well enough to accurately identify patients with meningitis, and traditionally described lumbar puncture results for viral and bacterial disease cannot always predict bacterial meningitis 3
• Fungal meningitis: no specific information available in the provided studies

Symptoms of Meningitis

• Classic symptoms of bacterial meningitis: fever, neck stiffness, altered mental status, and headache 2
• Certain patient populations, such as the young and the immunocompromised, may have a blunted presentation 2

Treatment of Meningitis

• Antibiotic therapy should be initiated as soon as possible because early treatment is associated with a better outcome 2
• The use of the corticosteroid dexamethasone has been shown to be helpful as an adjuvant therapy in specific clinical situations 2
• Ceftriaxone or cefotaxime is now the preferred drug for bacterial meningitis caused by H. influenzae, meningococci, and pneumococci 4
• Meropenem is a carbapenem antibiotic which is highly active against the major bacterial pathogens causing meningitis, and penetrates well into the cerebrospinal fluid 5
• Ceftriaxone and cefotaxime are both effective in the treatment of bacterial meningitis, with ceftriaxone offering an advantage in case of administration since it is administered as a single daily dose 6

Diagnosis of Meningitis

• Physical examination may not perform well enough to accurately identify patients with meningitis 3
• Lumbar puncture results for viral and bacterial disease cannot always predict bacterial meningitis 3
• Clinicians must have a high index of suspicion for bacterial meningitis, and certain patient populations may require an especially low threshold for obtaining a lumbar puncture 2