Meningitis, Pneumococcal

For further information, see CMDT Part 33-03: Pneumococcal Infections

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 meningitis in adults and the second most common cause of meningitis in children over the age of 6 years

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

• Penicillin-resistant strains may cause meningitis

Demographics

• Until 2000, S pneumoniae infections caused 100,000–135,000 hospitalizations for pneumonia, 6 million cases of otitis media, and 60,000 cases of invasive disease, including 3300 cases of meningitis

• Disease figures are now changing due to conjugate vaccine introduction

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

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

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), ceftriaxone, 4 g intravenously, should be given after blood cultures (positive in 50% of cases) have been obtained

• If gram-positive diplococci are present on the Gram stain, then vancomycin, 30 mg/kg/day intravenously in two divided doses, should be administered in addition to ceftriaxone until the isolate is confirmed not to be penicillin-resistant

• Once susceptibility to penicillin has been confirmed, penicillin, 24 million units daily intravenously in six divided doses, or ceftriaxone, 4 g/day as a single dose or as two divided doses, is recommended

• For severe penicillin allergy, chloramphenicol, 50 mg/kg every 6 hours, is an alternative (failures have occurred with penicillin-resistant strains)

• Duration of therapy is 10–14 days in documented cases

• 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 divided doses, is recommended

• Give 10 mg of dexamethasone intravenously immediately prior to or concomitantly with the first dose of appropriate antibiotic and every 6 hours thereafter for a total of 4 days

Follow-Up

• If a patient with a penicillin-resistant organism has not responded to a third-generation cephalosporin, repeat lumbar puncture is indicated to assess the bacteriologic response

Complications

• Hearing loss

• Residual neurologic deficit

Prevention

• Pneumococcal vaccine recommendations (Table 30–7)

Prognosis

• Patients presenting with depressed levels of consciousness have a worse outcome

• Dexamethasone administered with antibiotic to adults with meningitis has been associated with a 60% reduction in mortality and a 50% reduction in unfavorable outcome, primarily in patients with pneumococcal meningitis

When to Refer

• Consider early referral to an infectious disease specialist

When to Admit

• All patients with suspected bacterial meningitis