ACUTE BACTERIAL MENINGITIS

doi:10.1016/S0891-5520(05)70327-5

Infectious Disease Clinics of North America

Volume 10, Issue 4, 1 December 1996, Pages 797-809

https://doi.org/10.1016/S0891-5520(05)70327-5 Get rights and content

Meet the disease at its first stage. PERSIUS (AD 34–62) Satires

Acute bacterial meningitis remains a significant cause of morbidity and mortality in the United States. It now appears that the microbiologic epidemiology of this potentially devastating disease is changing. We have seen a decrease in the incidence of Haemophilus influenzae meningitis and the emergence of high-level penicillin resistance in Streptococcus pneumoniae –related disease. These developments affect the recommendations for initial empiric therapy of acute bacterial meningitis. This article reviews the epidemiology, clinical presentation, approaches to diagnosis, and the early therapy of acute bacterial meningitis.

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EPIDEMIOLOGY

The incidence of acute bacterial meningitis in the United States is approximately three cases per 100,000 persons per year.³⁷ The most common organisms have varied according to the population studied. H. influenzae type B was, until recently, the most common cause of endemic bacterial meningitis in childhood, followed by Neisseria meningitidis and S. pneumoniae.⁴¹ Following the introduction of widespread use of effective vaccines for H. influenzae type B, there was a significant decline in the

MICROBIOLOGY

As noted, S. pneumoniae, H. influenzae type B, and N. meningitidis are the major causes of community-acquired meningitis. H. influenzae is becoming increasingly resistant to commonly used antimicrobials. Approximately 30% of type B strains and 15% of non–type B strains are β-lactamase producers, which are resistant to ampicillin. These β-lactamase producers are occasionally resistant to second-generation cephalosporins such as cefuroxime.

N. meningitidis remains an important cause of morbidity

PRESENTING SIGNS AND SYMPTOMS

Classically, patients present with headache, fever, and meningismus with or without altered mental status. These signs and symptoms are eventually found in 85% of patients with acute bacterial meningitis.¹² The presenting signs and symptoms of meningitis, however, can be nonspecific. This is especially true in infants, young children, and the elderly. All physicians who manage such patients should have a high index of suspicion for meningitis. No one clinical sign or symptom is pathognomonic of

MORBIDITY AND MORTALITY

The severity of illness on presentation may be the one factor most predictive of outcome. In a recent study, the presence of coma, respiratory distress, shock, CSF protein level greater than 250 mg/dL, peripheral white blood cell count of less than 5,000/μL, and a serum sodium of less than 135 mEq/L on admission were associated with mortality.²¹ Significant neurologic sequelae were associated with the presence of coma and a CSF glucose level of less than 10 mg/dL on admission. Children died of

DIAGNOSIS

The diagnosis of acute bacterial meningitis is made by obtaining CSF. In the absence of a contraindication, lumbar puncture should be performed whenever meningitis is suspected. In acute bacterial meningitis, the CSF white blood cell (WBC) count is classically more than 1000/μL with a neutrophilic predominance. Many patients, however, will have fewer than 1000 WBC/μL, and about 10% may present with a lymphocyte predominance. This latter pattern is seen more often in the neonate, in patients

DIFFERENTIAL DIAGNOSIS

The major disease that needs to be differentiated from acute bacterial meningitis is acute viral meningitis. Although viral meningitis may be associated with an initial neutrophilic pleocytosis, there is a change to lymphocytes within 12 to 24 hours.¹¹ Adverse drug reactions due to nonsteroidal anti-inflammatory drugs, chemical meningitis due to craniopharyngiomas, carcinomatous meningitis, and parameningeal foci of infection can also cause a neutrophilic pleocytosis. The cell counts are

THERAPY

The prompt diagnosis of bacterial meningitis is imperative. Untreated this is a fatal disease. It is generally accepted that early effective antibiotic therapy improves survival and decreases neurologic sequelae (Table 2, Table 3). Tunkel and Scheld⁴² suggest that antimicrobial treatment appropriate for bacterial meningitis should be begun within 30 minutes of presentation for medical care. Some have questioned this notion.²⁹ This opinion was based on retrospective studies that compared

PREVENTION

The preferable intervention to decrease morbidity and mortality of bacterial meningitis is to prevent or eliminate colonization and infection with the offending organism. This can occur either through the use of immunization or chemoprophylaxis. The development and use of conjugate vaccine effective against H. influenzae type B in children as young as 2 months of age has resulted in a significant decline in the incidence of H. influenzae meningitis.¹ Part of this success likely relates to a

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