Chapter 16

### EPIDEMIOLOGY

Prior to the introduction of sulfonamides (late 1930s) and antibiotics (mid-1940s), a diagnosis of neonatal meningitis was almost always a death sentence. For the few who survived, severe neurologic sequelae were likely to occur. Subsequent to the introduction of antimicrobials, deaths were still common.

During the last 25 years, there has been an apparent decrease in both the incidence and the case fatality of neonatal bacterial meningitis in developed countries. The probable reason for this is a more aggressive approach to eradication of maternal colonization by those bacteria most commonly associated with early-onset (EO) meningitis. One of the most common organisms causing EO meningitis in the latter part of the 20th century was the group B streptococcus (GBS; also called Streptococcus agalactiae). However, in the 1990s, an aggressive approach to the elimination of GBS in both mother and infant was adopted to prevent neonatal sepsis and meningitis. Nevertheless, GBS and Escherichia coli (E. coli) remain the predominant organisms causing EO neonatal sepsis and meningitis. Recent figures from the USA (using the National Institute for Child Health and Human Development [NICHD] network) indicate that 43% of EO sepsis and meningitis were caused by GBS and 29% by E. coli. GBS occurred mostly in term infants (73%), whereas E. coli occurred predominantly in preterm infants (81%).1

It may be difficult to distinguish between sepsis and meningitis in the neonate, and they are often reported together. EO sepsis and meningitis are sometimes considered to be that which occurs within the first 3 days after birth (which may be considered as perinatal, with infection transmitted by the mother) and sometimes as that which occurs within the first week after birth (which might also include some cases of nosocomial infection, ie, hospital-acquired). There seems to be greater unanimity about the definition of late-onset (LO) meningitis, which is generally regarded as that which occurs more than 7 days after birth. At present, most cases of GBS meningitis are LO.

Although it may be difficult to distinguish clinically between sepsis and meningitis in the neonate, a diagnosis of bacterial meningitis usually requires a culture of cerebrospinal fluid (CSF) that is positive for pathogenic bacteria. However, if CSF cannot be obtained before administration of antibiotics, a diagnosis of meningitis may be supported by CSF pleocytosis and decreased CSF glucose (and increased CSF protein).

In addition to GBS, the other major organism associated with neonatal meningitis is E. coli, but Klebsiella species have also been implicated frequently in some countries, and Listeria monocytogenes accounts for a substantial number of LO cases in other countries. GBS and E. coli remain the predominant organisms causing both EO and LO meningitis in France. The distribution of organisms at different gestational ages, as well as different ages of onset, can be seen in Figure 16-1.2 Although only a handful of bacteria are commonly associated with ...

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