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, a group of antibiotics sometimes used to treat antibiotic-resistant 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.
New England Journal of Medicine