2. Purulent meningitis: etiology, clinical picture, diagnosis, treatment, prevention.

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Searching PubMed

bacterial meningitis treatment outcomes

I now have comprehensive data from the textbooks. Let me compile the full answer.

Purulent (Bacterial) Meningitis

1. Definition

Purulent meningitis is an acute inflammatory infection of the pia mater, arachnoid membrane, and the cerebrospinal fluid (CSF) filling the subarachnoid space, caused by pyogenic bacteria. The inflammatory process extends throughout the subarachnoid space around the brain and spinal cord and involves the ventricles. It evokes a polymorphonuclear (neutrophilic) pleocytosis in the CSF - the hallmark that distinguishes it from viral or tuberculous meningitis.

Goldman-Cecil Medicine, p. 3997

2. Etiology

The causative organism is strongly age-dependent:

Age Group	Most Common Pathogens
0-1 month	Group B Streptococci, Listeria monocytogenes, E. coli, S. pneumoniae
1-3 months	Group B Strep, L. monocytogenes, S. pneumoniae, N. meningitidis, H. influenzae, E. coli
3 months - 18 years	S. pneumoniae, N. meningitidis, H. influenzae
18-50 years	S. pneumoniae, N. meningitidis, H. influenzae
>50 years	S. pneumoniae, L. monocytogenes, gram-negative bacilli

Textbook of Family Medicine 9e, p. 1232

Key points on specific pathogens:

S. pneumoniae is now the most common cause in adults (~70% in developed countries), replacing H. influenzae after widespread Hib vaccination.
N. meningitidis predominates in children and young adults living in close quarters (dormitories, military barracks). Serogroups A, B, and C are most important.
Listeria is disproportionately common in the elderly, neonates, pregnant women, and immunocompromised patients.
Hospital-acquired meningitis (post-neurosurgery/trauma) features coagulase-negative staphylococci, S. aureus, Cutibacterium acnes, and Pseudomonas aeruginosa.

Predisposing factors: otitis media (most common), sinusitis, mastoiditis, CSF leak after closed-head trauma, alcoholism, asplenia, immunosuppression, perinatal exposure.

Rosen's Emergency Medicine, p. 2268

3. Pathogenesis

Nasopharyngeal colonization - organisms adhere to mucosal epithelium and invade the bloodstream (bacteremia).
BBB invasion - bacteria cross the blood-brain barrier into the CSF. Host defenses within the CSF (low complement, low immunoglobulin) are ineffective.
Bacterial proliferation - rapid growth triggers cytokine release (TNF-alpha, IL-1, IL-6).
Inflammatory cascade - leukocyte recruitment, increased BBB permeability, cerebral vasculitis, cerebral edema, and raised intracranial pressure (ICP).
Ischemia - reduced cerebral blood flow leads to cerebral hypoxia and neuronal injury.

Rosen's Emergency Medicine, p. 2268

4. Clinical Picture

Classic triad (present in ~85% of adults):

Fever
Severe headache
Nuchal rigidity (neck stiffness)

Additional findings:

Nausea/vomiting (35%)
Seizures (~30%)
Photophobia and phonophobia
Altered consciousness, confusion, lethargy, obtundation
Cranial nerve palsies and focal neurologic deficits (10-20%)
Kernig sign: resistance to knee extension after hip and knee flexion
Brudzinski sign: involuntary knee flexion on rapid neck flexion
Petechial/purpuric rash on extremities - hallmark of meningococcal meningitis

Age-specific presentations:

Neonates: poor feeding, irritability, vomiting, temperature instability, apnea; fontanelle bulging occurs late; nuchal rigidity unreliable.
Elderly: more insidious onset; variable or absent meningeal signs; change in mental status without fever common.

Warning sign: Papilledema appearing early should redirect attention to brain abscess or mass lesion.

Textbook of Family Medicine 9e, p. 1232

5. Diagnosis

Lumbar Puncture (LP) - the cornerstone

Perform LP as soon as bacterial meningitis is suspected, but first obtain a CT head if ANY of the following are present:

Criterion for CT Before LP
Immunocompromised state (HIV, transplant, immunosuppressants)
History of CNS disease (mass lesion, stroke, focal infection)
New-onset seizure (within 1 week)
Papilledema
Abnormal level of consciousness
Focal neurologic deficit

Typical CSF findings:

Parameter	Bacterial Meningitis	Viral Meningitis
Opening pressure (mm H2O)	>180	Often normal
Leukocyte count (cells/mm3)	1000-10,000 (median 1195)	<300 (median 100)
Neutrophils	>80%	<20%
Glucose (mg/dL)	<40	>40
Protein (mg/dL)	100-500	Often normal
Gram stain positivity	60-90%	Negative
Culture positivity	70-85%	50%

Textbook of Family Medicine 9e, p. 1233

Additional diagnostics:

Gram stain: rapid organism identification, specificity >97%; sensitivity 60-90%.
Blood cultures: before antibiotics whenever possible.
CBC (leukocytosis), platelet count, PT/PTT, metabolic panel, ABGs.
PCR (FilmArray meningitis/encephalitis panel): especially useful when Gram stain is negative or antibiotics already given.
Serum CRP: high negative predictive value; useful if withholding antibiotics is being considered with a negative Gram stain.
Latex agglutination / Limulus lysate assay: not shown to be clinically useful routinely.
Imaging: chest X-ray, sinus/skull radiograph as clinically indicated.

6. Treatment

Bacterial meningitis is a neurologic emergency. Antibiotics must be started immediately - after LP if safe, or after blood cultures if LP/CT is required first.

A. Empiric Antibiotic Therapy (before organism identified)

Standard adult regimen (community-acquired):

Ceftriaxone 2 g IV q12h (or cefotaxime 3 g IV q6h)
+ Vancomycin 15-20 mg/kg IV q8h (to cover penicillin/cephalosporin-resistant pneumococcus)
+ Ampicillin 2 g IV q4h - add in patients >50 years and neonates (coverage for Listeria, which is cephalosporin-resistant)

Hospital-acquired/post-neurosurgical meningitis:

Replace ceftriaxone with cefepime 2 g IV q8h for broader gram-negative coverage including Pseudomonas.

Cephalosporin allergy:

Meropenem or chloramphenicol.
Linezolid 600 mg q12h or moxifloxacin 400 mg OD with vancomycin for resistant pneumococcus.

Neonates: Avoid ceftriaxone (displaces bilirubin from albumin); use cefotaxime instead.

B. Targeted Antibiotic Therapy (by Gram stain/culture)

Organism	First-Line	Alternative
S. pneumoniae	Vancomycin + 3rd-gen cephalosporin	Meropenem, fluoroquinolone
N. meningitidis	3rd-gen cephalosporin	Penicillin G, ampicillin, chloramphenicol
L. monocytogenes	Ampicillin (+/- gentamicin)	TMP-SMX, meropenem
H. influenzae	3rd-gen cephalosporin	Chloramphenicol, cefepime, meropenem

Duration of therapy is pathogen-based (typically 7-14 days for most organisms, 21 days for Listeria and gram-negative bacilli).

C. Adjunctive Corticosteroid Therapy

Dexamethasone 0.15 mg/kg IV (max 10 mg) q6h for 4 days

Must be given with or 20 minutes before the first dose of antibiotics to be effective.
Do NOT give if antibiotics have already been started.
Benefits: reduces mortality in pneumococcal meningitis; reduces hearing loss in H. influenzae meningitis.
Discontinue if Listeria is identified (dexamethasone is associated with worse outcomes in Listeria CNS infection).
Evidence for benefit limited to high-income country settings.
Rosen's Emergency Medicine, p. 2276; Textbook of Family Medicine 9e, p. 1235

D. Supportive Care

IV fluids, monitoring of electrolytes (watch for SIADH)
Seizure management
Management of raised ICP (head elevation 30°, osmotherapy with mannitol if needed)
ICU admission for severely ill patients

7. Prevention

A. Chemoprophylaxis (post-exposure)

Indicated for close contacts of patients with documented meningococcal or H. influenzae type B meningitis (household contacts, healthcare workers with direct exposure to oral secretions).

Meningococcal meningitis:

Rifampin 600 mg PO twice daily x 2 days (adults); 10 mg/kg q12h x 2 days (children >1 month); 5 mg/kg q12h (infants <1 month)
Alternative: Ceftriaxone IM single dose - 125 mg if ≤15 years; 250 mg if >15 years
Rifampin is contraindicated in pregnancy; note it reduces efficacy of oral contraceptives.

H. influenzae (Hib) meningitis:

Rifampin 20 mg/kg (max 600 mg) OD x 4 days for household contacts where any child <4 years is not fully vaccinated.
Textbook of Family Medicine 9e, p. 1235

B. Vaccination (primary prevention)

Vaccine	Target Pathogen	Target Population
Hib conjugate vaccine	H. influenzae type B	Routine childhood immunization
Pneumococcal (PCV13, PPSV23)	S. pneumoniae	Children, adults ≥65, asplenic/immunocompromised
Meningococcal conjugate (MenACWY)	N. meningitidis serogroups A, C, Y, W-135	Adolescents, college freshmen, military recruits, travelers to endemic areas
Meningococcal serogroup B (MenB)	N. meningitidis serogroup B	Adolescents/young adults (particularly prevalent in Europe)

Vaccination has dramatically reduced bacterial meningitis incidence (to 0.5-1.5 per 100,000 adults in developed countries), though overall mortality (~15%) has not improved despite lower case numbers.

Goldman-Cecil Medicine, p. 3997; Rosen's Emergency Medicine, p. 2268

8. Complications and Prognosis

Mortality ~15% overall; highest with Listeria (~27%) and pneumococcal meningitis.
Neurologic sequelae: sensorineural hearing loss (most common), cognitive impairment, focal deficits, seizure disorder, hydrocephalus.
Pneumococcal meningitis has the highest rate of residual neurologic deficit.
A 2026 meta-analysis (PMID: 41761295) found sequelae are commonly underdetected at clinical review; a 2024 meta-analysis of 80 years of data (PMID: 39093565) confirmed global case fatality remains substantial and has not declined significantly.

Sources:

Textbook of Family Medicine, 9th ed. (Rakel), pp. 1231-1235
Rosen's Emergency Medicine, pp. 2268-2276
Goldman-Cecil Medicine (International Edition), p. 3997

This is a shared conversation. Sign in to Orris to start your own chat.