BACTERIAL SEPSIS AND MENINGITIS - Nizet Laboratory at UCSD

Birth Weight
The factor associated most significantly with enhanced
risk for bacterial sepsis and meningitis in neonates is low
birth weight (see Tables 6–5 and 6–9) [12,18,270–272].
Infection is the most common cause of death in infants
with very low birth weight [271,272]. With the exception
of infection caused by GBS, it is unusual for a term infant
to develop early-onset sepsis after an uneventful pregnancy
and delivery. In a study in England and Wales,
neonates weighing less than 2000 g at birth acquired
meningitis six times more frequently than infants weighing
more than 2000 g [26]. The lower the infant’s birth
weight, the higher is the incidence of sepsis (see
Table 6–5). An Israeli study of 5555 very low birth weight
infants documented the increased risk of late-onset sepsis
with decreasing birth weight; late-onset sepsis occurred in
16.8% of neonates with a birth weight of 1250 to 1500 g,
30.6% of neonates weighing 1000 to 1249 g, 46.4% of
neonates weighing 750 to 999 g, and 53% of neonates
weighing less than 750 g at birth [16]. In a study of infants
in Atlanta (see Table 6–9), the importance of birth weight
was identified as a predisposing factor for development of
early-onset and late-onset sepsis. If very low birth weight
infants survived the first days of life, rates of sepsis
decreased, but remained elevated [267]; 16% of 2416
infants with birth weights of 501 to 1500 g who were
enrolled in a study sponsored by NICHD developed
sepsis at a median of 17 days of age [18].
Risk Factors of Infant and Mother
The relative importance of other factors associated with
systemic infection in the newborn is more difficult to
define. In their prospective study of 229 infants with sepsis
and meningitis, Greenberg and coworkers [12] found
that certain conditions were common: 130 (57%) were
premature (24 hours) interval after
rupture of maternal membranes. Investigators in Pakistan
[273] found that maternal urinary tract infection, maternal
fever, vaginal discharge, and vaginal examinations
during labor were maternal factors significantly associated
with neonatal early-onset sepsis, whereas low Apgar
scores at birth and the need for endotracheal intubation
were significant neonatal risk factors.
Attack rates for early-onset group B streptococcal sepsis
in a study from Chicago [274] were affected by birth
weight, duration of rupture of membranes, and occurrence
of maternal peripartum fever. Infants with one or
more of these perinatal risk factors had an attack rate of
8 per 1000 live births and a mortality rate of 33% compared
with infants without such risk factors, who had an
attack rate of 0.6 per 1000 live births and a mortality rate
of 6% (Table 6–10).
Maternal fever during labor or after delivery suggests a
concurrent infectious event in the mother and infant, but
noninfectious events may be responsible for maternal
fever. Use of epidural analgesia for pain relief during
labor is associated with increases in maternal temperature.
TABLE 6–10 Relationship of Attack Rates and Fatalities of
Neonatal Group B Streptococcal Early-Onset Disease to Perinatal
Characteristics
Characteristic
Birth weight (g)
Attack Rate
per 1000
Live Births
Mortality
Rate (%)
2500 1 3
Rupture of membranes (hr)
48 11 33
Peak intrapartum temperature ( C)
37.5 7 17
Perinatal risk factors
CHAPTER 6 Bacterial Sepsis and Meningitis
Present 7.6 33
Absent 0.6 6
Total no. infants ¼ 32.384 2 26
239
Data from Boyer KM, et al. Selective intrapartum chemoprophylaxis of neonatal group B
streptococcal early-onset disease, I: epidemiologic rationale. J Infect Dis 148:795-801, 1983.
Intrapartum fever of more than 38 C (>100.4 F)
occurred an average of 6 hours after initiation of epidural
anesthesia in 14.5% of women receiving an epidural anesthetic
compared with 1% of women not receiving an epidural
agent; the rate of fever increased from 7% in
women with labors of less than 6 hours to 36% in women
with labors lasting longer than 18 hours. There was no
difference in the incidence of neonatal sepsis in the
infants born to 1045 women who received epidural analgesia
(0.3%) compared with infants born to women who
did not have epidural analgesia (0.2%) [275]. Fetal core
temperature may be elevated during maternal temperature
elevation, and increased temperature may be present
transiently in the neonate after delivery.
Ethnicity
The Collaborative Perinatal Research Study provides
historical information on 38,500 pregnancies [276];
selected data for white and black women are presented
in Table 6–11. Black women had a higher rate of premature
rupture of membranes lasting more than 24 hours
(21.4%) compared with white women (10.8%), black
women had a higher rate of puerperal infection (4.1%)
compared with white women (3.6%), and more black
infants weighed less than 2500 g at birth (13.4%) compared
with white infants (7.1%). More recent published
data concur with the data observed 30 years ago. The
National Center for Health Statistics reported continued