Bacterial Meningitis
Arnold L. Smith MD1
1 Professor, Departments of Pediatrics and Microbiology, School of Medicine, University of Washington; Chief, Division of Infectious Disease, Children's Hospital and Medical Center, Seattle, WA.
Bacterial meningitis is a serious, relatively common childhood disease that affects approximately 1 in 500 children who are younger than 2 years. Although its presentation can be dramatic, the child who has meningitis most commonly comes to medical attention with signs and symptoms not markedly different from those of a benign, self-limited childhood illness. Thus, the physician must be alert to the clues of bacterial meningitis.
Etiology
NEONATAL
The agents causing bacterial meningitis vary markedly with the age of the affected child. The neonate is unique in that the Streptococcus agalactiae (group B streptococcus) and Escherichia coli (particularly capsular type K1) cause three fourths of all infections (Table 1). The greatest risk factor for infection in neonates is prematurity. Obstetric complications or maternal illness also place the infant at increased risk for infection. This is probably due to the additional amount of invasive monitoring and therapy, as well as to increased contact with caregivers, that infants from high-risk mothers require. As might be expected, any other illness intrinsic to the infant (eg, congenital abnormality requiring surgery) also places the infant at increased risk.
INFANCY
In infants, Haemophilus influenzae is the most common bacterium causing meningitis (Table 1). Although vaccines for this illness are generally efficacious and currently are recommended, the physician must be alert for the potential for this disease until widespread utilization occurs and vaccine efficacy is documented in the general United States population.
