Researchers
Discover Shift in Organisms Causing Early-Onset Sepsis in Low-Birth-Weight
Infants
Change From Primarily Gram-Positive to Gram-Negative Organisms Raises
Concerns
Although the
overall rate of early-onset sepsis in low-birth-weight newborns has
not changed significantly over the past decade, researchers have discovered
a recent shift in the organisms responsible for the systemic infection
— from primarily gram-positive bacteria to primarily gram-negative organisms,
especially E. coli. The researchers, who believe further studies
are needed to determine the reason for this change, consider it worrisome
because of the high mortality rate associated with gram-negative infections.
The study was reported in the July 25 issue of the New England Journal
of Medicine.
The study was performed by
principal investigator Barbara J. Stoll, M.D., professor of pediatrics
at Emory University School of Medicine, and her colleagues at the centers
comprising the Neonatal Research Network of the National Institute of
Child Health and Human Development (NICHD), part of the National Institutes
of Health (NIH).
Systemic infection is an
important cause of illness and death among very low-birth-weight infants
(less than 1500 g), particularly within the first 72 hours after birth.
The researchers studied the pathogens involved in early-onset sepsis
in a group of 5,447 very-low-birth-weight infants (401 to 1500 g) born
between 1998 and 2000 and compared them to the pathogens involved in
early-onset sepsis in a group of 7,606 very-low-birth-weight infants
born between 1991 and 1993.
The researchers found that
the overall incidence of sepsis in the two groups of infants did not
differ significantly, but there was a significant change in the bacteria
involved in the infections. In the more recent group of infants, there
was a significant reduction in group B streptococcal sepsis compared
to the earlier group (from 5.9 to 1.7 per 1000 live births under 1500
g), but an increase in E. coli sepsis (from 3.2 to 6.8 per 1000
live births under 1500 g). Eighty-five percent of the E.coli
cases were resistant to ampicillin. Although there were no significant
differences in the rates of early infection between infants whose mothers
received antibiotics during labor and delivery and those who did not,
mothers of infants with ampicillin-resistant E. coli infections
were more likely to have received intrapartum ampicillin than those
with E. coli strains that were responsive to ampicillin. All
of the E. coli infections were sensitive to third-generation
cephalosporins, and most were sensitive to gentamicin — other antibiotics
used to treat gram-negative infections.
"The shift in the distribution
of organisms associated with early-onset sepsis is particularly worrisome
because of the high mortality rate associated with gram-negative infections,"
said Dr. Stoll. "This study has raised concerns that increasing use
of antibiotics during labor and delivery might be resulting in changes
in the kinds of organisms involved in infection of preterm infants and
their susceptibility to antibiotics. These findings warrant follow-up
studies to determine if these changes will persist over time and to
explain the reason for this shift in early-onset pathogens."
In addition to Emory, centers
in the Neonatal Research Network involved in the study included Brown
University, Harvard University, Indiana University, Stanford University,
the University of Alabama, the University of Miami, the University of
New Mexico, the University of Tennessee, the University of Texas-Dallas,
the University of Texas-Houston, Wayne State University and Yale University.
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