Chapter 61

• Early meningitis is not easy to diagnose. Especially in young infants, signs and symptoms are notoriously nonspecific.
• Organisms enter the cerebrospinal fluid by hematogenous spread or by direct extension from the nasopharynx or other adjacent structures. Many of the pathologic changes are not primarily due to infection but result from the response of the human immune system to the infection.
• An increasing majority of all cases of meningitis are aseptic and most of these cases have a benign outcome.
• For children younger than 1 month, the predominant organisms are group B Streptococcus, Escherichia coli, and Listeria monocytogenes.
• The incidence of Haemophilus influenzae type b, which was the most common etiologic agent of childhood bacterial meningitis, has dropped dramatically since the introduction of the conjugate vaccine against this organism. Streptococcus pneumoniae is now the major cause of infant bacterial meningitis in the United States and Neisseria meningitidis is the most common cause in the 2- to 18-year age group.
• Neonatal cerebrospinal fluid contains more cells and protein and less glucose than that of older children.
• Newborns are generally treated with an initial dose of ampicillin, 100 mg/kg, and an aminoglycoside, such as gentamicin, 2.5 mg/kg. Depending on local sensitivities, a cephalosporin active against gram-negative bacilli, such as cefotaxime, 50 mg/kg, may be substituted for the aminoglycoside.
• Vancomycin is the only antibiotic to which all strains of pneumococci are susceptible and it is therefore added to a broad-spectrum cephalosporin for comprehensive therapy (vancomycin, 15 mg/kg/dose bid, and cefotaxime, 50 mg/kg/dose tid) for infants and small children.
• In the unstable child, lumbar puncture should be withheld until after stabilization and antibiotic administration.
• Steroids may be beneficial in reducing the sequelae of bacterial meningitis. Major sequelae include hearing loss, seizures, and decreased mental ability.

Over the past 20 years, there has been a significant change in the epidemiology of bacterial meningitis, which is now predominantly a disease of adults. The most important contributor to this change has been the >99% decrease in frequency of H. influenzae type B (Hib), which was the most common etiologic agent of childhood bacterial meningitis, since the introduction of the conjugate Hib vaccine in the late 1980s.1,2 In 2006, there were only 29 cases of invasive H. influenzae type B reported in children younger than 5 years.3S. pneumoniae was the major cause of bacterial meningitis in infants 1 month to 2 years of age in the United States until the heptavalent pneumococcal conjugate vaccine (PCV7) that covers 80% of invasive serotypes was introduced in 2000. In 2005, there were 13 000 fewer cases of S. pneumoniae meningitis and bacteremia annually in children <5 years of age compared to 1998 to 1999, just prior to the introduction of the vaccine. The overall incidence of pneumococcal disease in this age group declined from 98.7 to 23.4 cases per 100 000.4 A 23-valent pneumococcal vaccine is also available for older children and adults with underlying diseases. N. meningitidis is now the most common cause of meningitis in infants and children, with a peak caused by serogroup B below age 2 and second peak at 18-year age. There is no vaccine for serogroup B. A ...

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