SAN FRANCISCO — The incidence of early-onset group B streptococcal disease fell significantly in term infants after 2002 recommendations called for culture-based screening of all pregnant women, Matthew Eberly, M.D., said.
A retrospective review of all 736,984 live births at U.S. Department of Defense hospitals from October 1992 to December 2004 found 828 term infants and 128 preterm infants who developed group B streptococcal (GBS) disease in the first 7 days of life, he said in a poster presentation at the annual meeting of the Infectious Diseases Society of America.
Dr. Eberly and his associates at the San Antonio Military Pediatric Center divided these births into three periods: the years before the Centers for Disease Control and Prevention's 1997 recommendations to give antibiotics to women who had either clinical high-risk factors for GBS colonization or culture results showing colonization; 1997 through November 2002, before the CDC's 2002 recommendation to screen all women via vaginal-rectal culture at 35–37 weeks' gestation; and December 2002 to the present (the period since the recommendation for universal culture-based GBS screening and treatment).
The incidence of early-onset GBS disease in all infants fell from a rate of 2.18 per 1,000 live births before 1997, to 0.84 per 1,000 through November 2002, and to 0.70 per 1,000 in the third period. The differences were significant. “The new guidelines since 2002 are more effective in preventing early-onset GBS disease,” he said.
The universal culture-based screening strategy did not reduce early-onset GBS infections in preterm infants, since cultures are not obtained until about 36 weeks' gestation.
As the incidence of early-onset GBS in term infants fell from 2.08 per 1,000, to 0.76 per 1,000, to 0.50 per 1,000 over time, the proportion of preterm infants among those with early-onset GBS disease increased from 10% to 15% to 33% over the three periods studied, he noted.
Of the 78 cases of early-onset GBS disease since the 2002 guidelines were issued, 26 occurred in preterm infants. Twelve weighed less than 1,000 g at birth, and 14 were delivered before 30 weeks' gestation. “These are the extremely low-birth-weight infants” who are most likely to develop early-onset GBS disease under the current strategy, Dr. Eberly said.