Meningitis, Pneumococcal

Key Features

Essentials of Diagnosis

• Fever, headache, altered mental status

• Meningismus

• Gram-positive diplococci on Gram stain of cerebrospinal fluid; counterimmunoelectrophoresis may be positive in partially treated cases

General Considerations

• Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults

• Head trauma, with cerebrospinal fluid leaks, sinusitis, and pneumonia may precede it

Clinical Findings

Symptoms and Signs

• Rapid onset, with fever, headache, and altered mentation

• Pneumonia may be present

• Compared with meningitis caused by the meningococcus

  • Pneumococcal meningitis lacks a rash

  • Obtundation, focal neurologic deficits, and cranial nerve palsies are more prominent features and may lead to long-term sequelae

Differential Diagnosis

• Meningitis due to other causes, eg, meningococcus, Listeria, aseptic

• Subarachnoid hemorrhage

• Encephalitis

• "Neighborhood reaction" causing abnormal cerebrospinal fluid, such as

  • Brain abscess

  • Epidural abscess

  • Vertebral osteomyelitis

  • Mastoiditis

  • Sinusitis

  • Brain tumor

• Dural sinus thrombosis

• Noninfectious meningeal irritation

  • Carcinomatous meningitis

  • Sarcoidosis

  • Systemic lupus erythematosus

  • Drugs (eg, nonsteroidal anti-inflammatory drugs, trimethoprim-sulfamethoxazole)

  • Pneumonia

  • Shigellosis

Diagnosis

Laboratory Tests

• See Table 30–1

• Cerebrospinal fluid

  • Typically has > 1000 white blood cells per microliter, over 60% of which are polymorphonuclear leukocytes

  • Glucose concentration is < 40 mg/dL (< 2.22 mmol/L), or < 50% of the simultaneous serum concentration

  • Protein usually exceeds 150 mg/dL (1500 mg/L)

  • Gram stain shows gram-positive cocci in up to 80–90% of cases

• In untreated cases, blood or cerebrospinal fluid cultures are almost always positive

• Fifty percent rate of bacteremia

• Antigen detection tests may occasionally be helpful in establishing the diagnosis in the patient who has been partially treated and in whom cultures and stains are negative

Treatment

Medications

• See Tables 30–5 and 30–2

• Give antibiotics as soon as the diagnosis is suspected

• If lumbar puncture must be delayed (eg, while awaiting results of an imaging study to exclude a mass lesion), the patient should be treated empirically for presumed meningitis with intravenous ceftriaxone, 2 g, plus vancomycin, 15 mg/kg, plus dexamethasone, 0.15 mg/kg administered concomitantly after blood cultures (positive in 50% of cases) have been obtained

• Once susceptibility to penicillin has been confirmed, penicillin, 24 million units intravenously daily in six divided doses, or ceftriaxone, 2 g every 12 hours intravenously, is continued for 10–14 days

• The best therapy for penicillin-resistant strains is not known. Susceptibility testing is essential

• If the minimum inhibitory concentration (MIC) of ceftriaxone or cefotaxime is ≤ 0.5 mcg/mL, single-drug therapy with either of these cephalosporins is likely to be effective

• When the MIC is ≥ 1 mcg/mL, treatment with a combination of ceftriaxone, 2 g every 12 hours, plus vancomycin, 30 mg/kg/day in two or three ...