Preventing Neonatal Group B Streptococcal Disease

PREVENTING NEONATAL GROUP B STREPTOCOCCAL DISEASE

Neonatal sepsis from Group B Streptococcus (GBS) has decreased since the introduction of organized prevention strategies in the mid 1990’s. The Centers for Disease Control (CDC), in collaboration with ACOG and AAP, have recently refined the strategies for preventing the mother to infant transmission of this potentially life-threatening organism. GBS is part of the normal bowel and vaginal flora for 10-20% of pregnant women. This colonization rarely causes problems during the pregnancy and the infant is usually first exposed at the time of labor and delivery. Without intervention, approximately half of the infants born to GBS colonized mothers become colonized and 1-2% show signs of invasive infection at birth or in the first week of life. By giving antibiotics during labor to mothers who are at risk for transmitting GBS to their infants, we reduce the chances that the baby will get early onset GBS disease.

There are two basic strategies for selecting mothers who would benefit from prophylactic antibiotics while they are in labor. One strategy is based on GBS cultures done late in pregnancy; the other is based on risk factors (generally considered to be rupture of membranes over 18 hours, fever in labor and preterm labor.) Data from many centers, including CPMC, show that the culture-based strategy is superior. Cultures of the lower vagina and rectum are collected as close to term as possible (generally 35-37 weeks) so the information is current and available in time for the delivery. A selective media must be used. The goal is to give intravenous antibiotics to the mother at least 4 hours before the delivery. Penicillin and ampicillin remain the recommended antibiotics for prophylaxis and the CDC guidelines discuss alternatives for the penicillin allergic mother. Prophylaxis is recommended for all GBS positive mothers who are in labor and in select cases when GBS status is unknown (primarily preterm labor.) Prophylaxis is elective for mothers delivering by planned cesarean who are not in labor and have intact membranes. Mothers who have previously delivered an infant with invasive GBS disease or those with urinary tract infections with GBS during the current pregnancy do not need screening cultures but should be given antibiotics in labor. Prevention schemes based on rapid testing in labor remain under investigation.

The last decade gave many of us an opportunity to become more comfortable with viewing “pre-treated” infants of GBS positive mothers as healthy babies who require no added evaluations. Infants with adequate maternal antibiotic prophylaxis can be discharged using the same criteria as their peers whose mothers are GBS negative. We need to remember that maternal antibiotics to prevent GBS may not 1) be sufficient to prevent all GBS disease, 2) fully treat a truly infected infant, or 3) be adequate treatment if the infant is heavily exposed to GBS (such as infants born to GBS positive mothers with definite chorioamnionitis.)

An algorithm to approach term infants at risk for infection is provided. It considers all infants, not just those with a GBS positive mother. For convenience, our antibiotic dosing regimen for newborns “ruling out sepsis” is included.

You can access more information and the full CDC guidelines on GBS at http://www.cdc.gov/groupbstrep/.

For an educational conference on this topic call CPMC Perinatal and Neonatal Outreach at (415-600-6356).



Antibiotic doses in first week of life:
Ampicillin: 50 mg/kg/dose, if < 2 kg give a dose q 12 hours, if >2 kg give a dose q 8 hours
Gentamicin: dose every 24 hours: if <26 weeks gestation = 2 mg/kg; 26-30 wks = 3 mg/kg;
31-36 wks = 3.5 mg/kg and >36 wks = 4 mg/kg