BACTERIAL SEPSIS AND MENINGITIS - Nizet Laboratory at UCSD

In tropical areas, a different pattern can be observed
[289–291]. In Riyadh, Saudi Arabia, from 1980-1984,
E. coli, Klebsiella species, and Serratia species were the
dominant causes of neonatal sepsis; GBS was an infrequent
cause [291]. Later data from this geographic location
revealed E. coli and CoNS were the most common
pathogens, however, causing early-onset and late-onset
sepsis [292].
Every year, 4 million neonatal deaths occur. About one
third of the deaths are due to sepsis [293,294]. The highest
numbers of neonatal deaths are in South Central Asian
countries and sub-Saharan Africa. The global perspective
of neonatal sepsis is discussed in Chapter 2. The most
common isolates responsible for neonatal sepsis vary by
country, but include a wide spectrum of gram-negative
and gram-positive species, the most common of which
are E. coli, S. aureus, Pseudomonas, and Klebsiella [295].
Multidrug-resistant strains are an increasing threat to
intervention programs [296,297].
GBS is the most frequent cause of early-onset and lateonset
sepsis in the United States, but the rates and risk
factors for maternal and neonatal GBS colonization and
disease vary in different communities [298–300]. Amin
and colleagues [298] in the United Arab Emirates evaluated
563 pregnant women from similar socioeconomic
and ethnic backgrounds and reported a GBS colonization
rate of 10.1%. In Athens, Greece, maternal and neonatal
colonization rates were 6.6% and 2.4% with a vertical
transmission rate of 22.5% [299]. Middle-class women
followed in the private setting were more frequently colonized
with GBS than women followed in a public hospital.
No association was found between colonization with
GBS and maternal age, nationality, marital status, previous
obstetric history, cesarean section, infant birth
weight, or preterm birth.
Stoll and Schuchat [300] reviewed data on female genital
colonization with GBS from 34 reports in the literature
and emphasized the importance of appropriate specimen
collection and inoculation into selective (antibioticcontaining)
broth media in the ascertainment of accurate
colonization rates. Analysis of data from studies employing
adequate methods revealed regional GBS colonization
rates of 12% in India and Pakistan, 19% in Asian and
Pacific countries, 19% in sub-Saharan Africa, 22% in the
Middle East and North Africa, and 14% in the Americas.
A comparison of studies that did and did not use selective
broth media revealed significantly higher GBS colonization
rates in the populations where selective broth media
was employed to assess colonization. Other reasons for
varying rates of GBS colonization and disease may include
socioeconomic factors or differences in sexual practices,
hygiene, or nutrition.
Socioeconomic Factors
The lifestyle pattern of mothers, including cultural practices,
housing, nutrition, and level of income, seems to
be important in determining infants at risk for infection.
The most significant factors enhancing risk for neonatal
sepsis are low birth weight and prematurity, and the
incidence of these is inversely related to socioeconomic
status. Various criteria for determining socioeconomic
CHAPTER 6 Bacterial Sepsis and Meningitis
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status have been used, but no completely satisfactory
and reproducible standard is available. Maternal education,
resources, and access to health care can affect the
risk of neonatal sepsis. A CDC report [301] evaluating
the awareness of perinatal group B streptococcal infection
among women of childbearing age in the United States
revealed that women with a high school education or less;
women with a household income of less than $25,000;
and women reporting black, Asian/Pacific Islander, or
other ethnicity had lower awareness of perinatal GBS
infections than other women.
Procedures
Most infants with very low birth weight have one or more
procedures that place them at risk for infection. Any disruption
of the protective capability of the intact skin or
mucosa can be associated with infection. In a multicenter
study of NICU patients, increased risk of bacteremia was
associated with parenteral nutrition, mechanical ventilation,
peripherally inserted central catheters, peripheral
venous catheters, and umbilical artery catheters [302].
NURSERY OUTBREAKS OR EPIDEMICS
The nursery is a small community of highly susceptible
infants where patients have contact with many adults,
including parents, physicians, nurses, respiratory therapists,
and diagnostic imaging technicians (see Chapter 35).
Siblings may enter the nursery or mothers’ hospital suites
and represent an additional source of infection. In these
circumstances, outbreaks or epidemics of respiratory and
gastrointestinal illness, most of which is caused by nonbacterial
agents, can occur. Spread of microorganisms to the
infant occurs by droplets from the respiratory tracts of parents,
nursery personnel, or other infants. Organisms can be
transferred from infant to infant by the hands of health care
workers. Individuals with open or draining lesions are especially
hazardous agents of transmission.
Staphylococcal infection and disease are a concern in
many nurseries in the United States (see Chapter 35).
Epidemics or outbreaks associated with contamination
of nursery equipment and solutions caused by Proteus species,
Klebsiella species, S. marcescens, Pseudomonas species,
and Flavobacterium also have been reported. An unusual
and unexplained outbreak of early-onset group B streptococcal
sepsis with an attack rate of 14 per 1000 live births
occurred in Kansas City during January through August
of 1990 [303].
Molecular techniques to distinguish among bacterial
strains are an important epidemiologic tool in the investigation
of nursery outbreaks. Previously, methods to
determine strain relatedness relied on antibiotic susceptibility
patterns, biochemical profiles, and plasmid or phage
analysis [154,304]. More recent techniques permit the discrimination
of strains based on bacterial chromosomal
polymorphisms. Pulse-field gel electrophoresis, ribotyping,
multilocus sequence typing, and polymerase chain
reaction–based methods are widely used tools to assign
strain identity or relatedness [305–307].
Antimicrobial agents play a major role in the ecology
of the microbial flora in the nursery. Extensive and