In an adult patient with suspected bacterial meningitis and no known drug allergies, which of the following are administered for treatment of purulent meningitis: a) vancomycin plus ceftriaxone, b) ceftazidime, c) antiviral agents, d) linezolid, e) dexamethasone?

Treatment of Purulent (Bacterial) Meningitis in Adults

For suspected bacterial meningitis in adults without drug allergies, the correct treatments are: (a) vancomycin plus ceftriaxone, (b) ceftazidime for specific pathogens only, (d) linezolid as alternative therapy for resistant organisms, and (e) dexamethasone as adjunctive therapy. Antiviral drugs (c) are not indicated for purulent bacterial meningitis.

Empiric Antibiotic Therapy

The standard empiric regimen for adult bacterial meningitis is vancomycin plus a third-generation cephalosporin (ceftriaxone or cefotaxime). 1

• Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours provides broad coverage against common meningeal pathogens including S. pneumoniae, N. meningitidis, and H. influenzae 1, 2

• Vancomycin 10-20 mg/kg IV every 8-12 hours (targeting serum trough concentrations of 15-20 μg/mL) must be added to cover penicillin- and cephalosporin-resistant pneumococci 1, 2

• This combination should never be replaced by vancomycin monotherapy, as vancomycin penetration into CSF may be inadequate, especially with concurrent dexamethasone use 1, 3

Role of Ceftazidime (Option b)

Ceftazidime is NOT part of standard empiric therapy for community-acquired bacterial meningitis. 4

• Ceftazidime is specifically indicated for meningitis caused by Pseudomonas aeruginosa and certain gram-negative organisms 1, 4

• It should be reserved for nosocomial meningitis, post-neurosurgical infections, or when Pseudomonas is identified 1

• For empiric community-acquired meningitis, ceftriaxone or cefotaxime are preferred over ceftazidime because they provide better pneumococcal coverage 1

Antiviral Drugs (Option c)

Antiviral agents have no role in the treatment of purulent (bacterial) meningitis. 2

• Purulent meningitis by definition is bacterial, characterized by neutrophilic pleocytosis and hypoglycorrhachia 2

• Antivirals would only be considered if viral meningitis/encephalitis is in the differential diagnosis, which is a separate clinical entity

Linezolid (Option d)

Linezolid is an alternative agent for specific resistant organisms, not first-line empiric therapy. 1

• Linezolid is recommended for methicillin-resistant S. aureus (MRSA) meningitis when vancomycin resistance (MIC >2 μg/mL) is present or vancomycin is contraindicated 1

• It is also an alternative for vancomycin-resistant enterococcal meningitis 1

• Linezolid is listed as alternative therapy for methicillin-resistant S. epidermidis 1

• It should not be used as empiric therapy for community-acquired bacterial meningitis in immunocompetent adults 1

Dexamethasone (Option e)

Dexamethasone should be administered as adjunctive therapy in adults with suspected or proven bacterial meningitis. 1, 2

Dosing and Timing

• Dexamethasone 10 mg IV every 6 hours for 4 days (or 0.15 mg/kg every 6 hours for 2-4 days) 1, 2

• Must be given 10-20 minutes before or simultaneously with the first antibiotic dose 1, 2

• If antibiotics have already been started, dexamethasone should still be initiated up to 12 hours after the first antibiotic dose 1

Evidence for Benefit

• In adults with bacterial meningitis, dexamethasone significantly reduced unfavorable outcomes (15% vs 25%, P=0.03) and mortality (7% vs 15%, P=0.04) 1

• The benefit was most pronounced in pneumococcal meningitis, with reduced unfavorable outcomes (26% vs 52%, P=0.006) and deaths (14% vs 34%, P=0.02) 1

• Dexamethasone appeared most beneficial in patients with moderate-to-severe disease on the Glasgow Coma Scale 1

Duration Guidance

• Continue dexamethasone for 4 days if pneumococcal meningitis is confirmed or thought probable based on clinical, epidemiological, and CSF parameters 1

• Stop dexamethasone if another cause of meningitis is confirmed or thought probable 1

Important Caveat with Vancomycin

• Dexamethasone may reduce vancomycin penetration into CSF 1, 3

• However, adequate CSF vancomycin concentrations can still be achieved with appropriate dosing (continuous infusion or higher intermittent doses targeting trough 15-20 μg/mL) 5

• Consider adding rifampin 300 mg every 12 hours to the vancomycin-ceftriaxone combination in suspected pneumococcal meningitis when dexamethasone is used, pending culture results 1

Special Populations Requiring Additional Coverage

For adults ≥50 years or immunocompromised patients, add ampicillin 2g IV every 4 hours to cover Listeria monocytogenes 1, 2

• Risk factors for Listeria include age >50, diabetes mellitus, immunosuppressive drugs, cancer, and other immunocompromising conditions 1, 2

Common Pitfalls to Avoid

• Never delay antibiotics for imaging or lumbar puncture – empiric therapy must begin within 1 hour of presentation 2

• Never use vancomycin alone – it must be combined with a third-generation cephalosporin 1

• Never omit vancomycin from empiric therapy – resistant pneumococcal strains remain a concern despite decreased prevalence 6

• Never give dexamethasone after antibiotics have been running for >12 hours – timing is critical for benefit 1

• Never use ceftazidime as empiric therapy for community-acquired meningitis – reserve it for Pseudomonas coverage 1, 4