The American Academy of Pediatrics (AAP) reaffirmed the American College of

Obstetricians and Gynecologists’ (ACOG) recommendation for the use of universal antenatal microbiologic testing for detecting maternal group B streptococcal (GBS) colonization to facilitate appropriate administration of intrapartum antibiotic prophylaxis, according to a clinical report recently published in Pediatrics.1 In addition, the report provides current recommendations for evaluating newborn infants at risk for GBS disease and treating those with confirmed GBS infection.

In July 2019, the ACOG updated its recommendation for performing universal GBS screening for all pregnant women between 36 weeks and 37 and 6/7 weeks of gestation.2 If vagino-rectal cultures are positive for GBS, patients should receive appropriate intrapartum antibiotic prophylaxis.2 In addition, intrapartum antibiotic prophylaxis is indicated for women under the following conditions:

  • GBS bacteriuria identified at any point during pregnancy
  • a history of a previous infant with GBS disease
  • preterm labor and/or with preterm prelabor rupture of membranes at <37 weeks’ gestation
  • labor onset at ≥37 weeks’ gestation with unknown GBS status if risk factors develop during labor

The recommended antibiotics for GBS intrapartum antibiotic prophylaxis to prevent neonatal GBS early-onset disease remain β-lactam antibiotics, with penicillin G identified as the preferred agent, with its narrower antimicrobial spectrum, but ampicillin is also acceptable.

For women with a penicillin allergy, the following antibiotics for GBS intrapartum antibiotic prophylaxis are recommended:

  • Cefazolin for women who are at low risk for anaphylaxis.
  • Clindamycin for women who are at high risk for anaphylaxis and who are colonized with GBS known to be susceptible to clindamycin.
  • Vancomycin for women who are at high risk for anaphylaxis if colonized with clindamycin-resistant GBS isolates.

For β-lactam antibiotics, administration of intrapartum antibiotic prophylaxis for at least 4 hours before delivery is most effective in preventing early-onset GBS disease. Researchers noted that the administration of cefazolin for at least 4 hours may provide adequate prophylaxis, because the pharmacokinetics and mechanism of bactericidal action for cefazolin are similar to those of penicillin and ampicillin. For clindamycin and vancomycin, however, there is “currently insufficient clinical efficacy evidence to consider the administration of these antibiotics equivalent to β-lactam antibiotics for the purpose of neonatal risk assessment,” noted the researchers.

In considering risk assessment for early-onset GBS infection, clinicians should follow current AAP clinical reports on management of neonates with suspected or proven early-onset bacterial sepsis.3,4 Risk for early-onset GBS infection should be considered separately for infants at or near term (≥35 weeks’ gestation) and for those preterm (≤34 6/7 weeks gestation). For infants born at or near term, early-onset GBS infection may be assessed with a categoric algorithm by using multivariate models such as the Neonatal Early-Onset Sepsis Calculator or with enhanced clinical observation. For infants born preterm, it may be best to use circumstances of preterm birth to determine management, as these infants are at highest risk for early-onset infection from all causes, including group B streptococci.

In terms of diagnosis, the routine measurement of complete blood cell counts or inflammatory markers such as C-reactive protein alone is not justified, given the poor test performance in predicting early-onset infection, especially among well-appearing infants at lowest baseline risk for infection. Instead, blood or cerebrospinal fluid culture should be used to diagnose early-onset GBS infection.

Empirical antibiotic therapy for early-onset and late-onset GBS disease differs by postnatal age at the time of evaluation. Penicillin G is the drug of choice, with ampicillin identified as an acceptable alternative therapy. The length of antibiotic therapy is generally 10 days for bacteremia without focus and 14 days for uncomplicated meningitis.

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Regarding future directions, researchers stressed that more research is needed to determine whether secondary effects of intrapartum antibiotic prophylaxis on the microbiome influence short- and long-term childhood health outcomes. Moreover, studies on vaccine development have shown safety and immunogenicity of glycoconjugate GBS vaccines. Because current surveillance data reveal that 99% of infections are caused by 6 GBS serotypes, a hexavalent vaccine could be widely effective, suggested the researchers.

References

1. Puopolo KM, Lynfield R, Cummings JJ; Committee on Fetus and Newborn; Committee on Infectious Diseases. Management of infants at risk for group B streptococcal disease. Pediatrics. 2019;144(2):e20191881.

2. American College of Obstetricians and Gynecologists. Prevention of group B streptococcal early-onset disease in newborns: ACOG committee opinion, number 782. Obstet Gynecol. 2019;134(1):e19-e40.

3. Puopolo KM, Benitz WE, Zaoutis TE; Committee on Fetus and Newborn; Committee on Infectious Diseases. Management of neonates born at ≥35 0/7 weeks’ gestation with suspected or proven early-onset bacterial sepsis. Pediatrics. 2018;142(6):e20182894.

4. Puopolo KM, Benitz WE, Zaoutis TE; Committee on Fetus and Newborn; Committee on Infectious Diseases. Management of neonates born at ≤34 6/7 weeks’ gestation with suspected or proven early-onset bacterial sepsis. Pediatrics. 2018;142(6):e20182896.