Abstract & Commentary

New CDC guidelines to prevent neonatal strep

Group B strep leading cause of neonatal sepsis

By Hal B. Jenson, MD, FAAP, Professor of Pediatrics, Tufts University School of Medicine, Boston, MA.

Dr. Jenson reports no financial relationships relevant to this field of study.

Synopsis: The 2002 guidelines for prevention of perinatal group B streptococcal disease have been updated with expanded recommendations on laboratory methods, revised algorithms for screening and intrapartum chemoprophylaxis, a change in the recommended dose of penicillin G, updated prophylaxis regimens for women with penicillin allergy, and a revised algorithm for management of newborns.

Source: Centers for Disease Control and Prevention: Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC, 2010. MMWR 2010;59(RR-10):1-32.

Group B streptococcal (GBS) disease is the leading cause of early-onset neonatal sepsis (within the first week of life) in the United States. Since the initial recommendations for perinatal prophylaxis in the 1990s, the incidence of GBS has declined by 80%. There are approximately 1,200 cases of early-onset GBS invasive disease each year in the United States, with 70% of cases among newborns ≥ 37 weeks' gestation.

GBS colonization is best determined by collecting both vaginal and rectal (through the anal sphincter) specimens at 35-37 weeks' gestation. Nucleic acid amplification tests (NAAT), such as PCR assays, can be used for GBS identification after an enrichment step. Enrichment increases sensitivity of detection from 54% to 92%-100%; the increased accuracy is much more important than the additional time required to obtain the result. Optical immunoassays and enzyme immunoassays are not sufficiently sensitive to detect GBS colonization reliably.

The double-disk diffusion method (D-zone test) or another validated test is recommended to identify isolates that are erythromycin-resistant and clindamycin-susceptible, which are presumed to have inducible resistance to clindamycin.

Intrapartum GBS prophylaxis is indicated for pregnant women with:

  • Previous infant with invasive GBS disease;
  • GBS bacteriuria during any trimester of the current pregnancy (except if cesarean delivery is performed before onset of labor with intact amniotic membranes);
  • Positive GBS vaginal-rectal screening culture in late gestation (optimally at 35-37 weeks' gestation);
  • Unknown GBS status at the onset of labor and any of the following:
  • Delivery at < 37 weeks' gestation;
  • Amniotic membrane ruptures ≥ 18 hours;
  • Intrapartum temperature ≥ 100.4°F (≥38.0°C); and
  • Intrapartum NAAT positive for GBS
  • Intrapartum GBS prophylaxis is not indicated for pregnant women with:
  • Colonization with GBS during a previous pregnancy;
  • GBS bacteriuria during a previous pregnancy;
  • Negative GBS vaginal-rectal screening culture (optimally at 35-37 weeks' gestation), regardless of intrapartum risk factors; and
  • Cesarean delivery performed before on set of labor with intact amniotic membranes, regardless of GBS colonization status or gestational age.

Penicillin G (5 million units IV initial dose, then 2.5-3.0 million units [using the dosing readily available on the hospital formulary] every four hours until delivery) remains the drug of choice for intrapartum antibiotic prophylaxis, with ampicillin (2 g IV initial dose, then 1 g IV every four hours until delivery) as an acceptable alternative. Penicillin-allergic women who do not have a history of anaphylaxis, angioedema, respiratory distress, or urticaria following administration of a penicillin or cephalosporin should receive cefazolin (2 g IV initial dose, then 1 g IV every 8 hours until delivery).

Antimicrobial susceptibility testing is necessary for GBS from penicillin-allergic women at high risk for anaphylaxis. These women should receive clindamycin if the GBS isolate is susceptible to clindamycin and also erythromycin (e.g., does not have inducible resistance to clindamycin). These women should receive vancomycin if the isolate demonstrates resistance (including inducible resistance) to clindamycin, or if susceptibility to clindamycin and erythromycin is unknown. Erythromycin is no longer an acceptable alternative for intrapartum GBS prophylaxis for penicillin-allergic women.

The management of newborns has also been updated:

  • Newborns with signs of sepsis should receive a full diagnostic evaluation (blood culture, CBC including white blood cell differential and platelet count, chest radiograph if abnormal respiratory signs are present, and a lumbar puncture if the newborn is stable) and antibiotic therapy;
  • Newborns of mothers with signs of chorioamnionitis should receive a limited evaluation (blood culture, and CBC with differential count and platelet count) with antibiotic therapy pending culture results;
  • Newborns of mothers who received intrapartum prophylaxis for ≥ 4 hours before delivery should be observed for ≥ 48 hours; and
  • Newborns who are well-appearing and born to mothers who had an indication for GBS prophylaxis but received no or inadequate (incorrect regimen, < four hours before delivery) prophylaxis:
  • Newborns ≥ 37 weeks and 0 days' gestation and duration of membrane rupture < 18 hours should be observed be for ≥ 48 hours, and no laboratory evaluation is recommended unless symptoms develop; and
  • Newborns < 37 weeks gestation or duration of membrane rupture ≥ 18 hours should have a limited evaluation and ob served for ≥ 48 hours.
  • Antibiotic therapy for newborns should include ampicillin for GBS as well as coverage for gram-negative pathogens, pending culture results.