What is the role of Penicillin administration in pregnant women with Group B Streptococcus (GBS) colonization?

From the Guidelines

Group B Streptococcus (GBS) screening is recommended for all pregnant women between 36-37 weeks gestation, with intrapartum antibiotic prophylaxis indicated for those who test positive, using intravenous Penicillin G as the first-line treatment, administered as a 5 million unit initial dose, followed by 2.5-3 million units every 4 hours until delivery, as supported by the most recent guidelines from the CDC 1. The guidelines emphasize the importance of universal screening and targeted antibiotic prophylaxis in reducing early-onset GBS disease by approximately 80% 1. For penicillin-allergic patients without anaphylaxis history, cefazolin 2g initial dose followed by 1g every 8 hours is recommended, while patients with severe penicillin allergy should receive clindamycin 900mg IV every 8 hours or vancomycin 1g IV every 12 hours (if susceptibility testing confirms sensitivity) 1. Prophylaxis should begin when labor starts or membranes rupture and continue until delivery, as this approach is crucial in preventing the transmission of GBS to the newborn, which can cause serious infections including sepsis, pneumonia, and meningitis 1. Key considerations in the management of GBS colonization during pregnancy include:

• Universal screening for GBS between 36-37 weeks gestation
• Intrapartum antibiotic prophylaxis for women who test positive
• Use of penicillin G as the first-line treatment, with alternative options for penicillin-allergic patients
• Initiation of prophylaxis at the onset of labor or membrane rupture and continuation until delivery
• Importance of susceptibility testing for patients with severe penicillin allergy to guide the choice of alternative antibiotics.

From the Research

Group B Streptococcus (GBS) and Penicillin Administration During Pregnancy

• Group B streptococci (GBS) are the leading cause of life-threatening neonatal bacterial infections in developed countries, with maternal vaginal carriage usually being asymptomatic 2.
• The risk of early neonatal GBS infection increases in cases of preterm delivery, maternal fever during delivery, and membrane rupture more than 18 hours before delivery, accounting for 50% to 75% of early neonatal GBS infections 2.
• Intrapartum antibiotic prophylaxis (IAP) in women who carry Group B streptococci reduces the risk of early-onset neonatal GBS infection from 4.7% to 0.4% (p = 0.02), with penicillin G being the antibiotic of choice 2.
• The estimated frequency of anaphylactic reactions to penicillin is about 5 cases per 10,000 treatments, which can have severe consequences for both mother and child 2.

Penicillin Administration and GBS Colonization

• Penicillin G remains the most reliable clinical antibiotic for IAP, with all 158 isolates in one study being penicillin G sensitive 3.
• However, clindamycin and erythromycin resistance is on the rise, with 32.9% of GBS isolates showing erythromycin resistance and 26.6% showing clindamycin resistance 3.
• The use of penicillin G as the primary antibiotic for IAP is recommended, with clindamycin or erythromycin as secondary options if allergies exist 3.

GBS Colonization and Disease among Pregnant Women

• Maternal GBS colonization is associated with early-onset neonatal sepsis, and extensive efforts are directed to preventing this complication 4.
• A historical cohort study found that 21.6% of the population was GBS colonized, and 0.1% had invasive GBS disease, with GBS colonization associated with younger maternal age, Black race, non-Hispanic ethnicity, chronic hypertension, preexisting diabetes, and tobacco use (p<0.01) 4.
• The study also found an increased risk of gestational diabetes in colonized pregnancies, and a decreased incidence of short cervix, chorioamnionitis, wound infection, and operative delivery 4.

Intrapartum Antibiotic Prophylaxis (IAP) and Neonatal Outcomes

• A retrospective study found that none of the newborns of mothers with GBS colonization and/or risk factors receiving IAP developed early-onset disease, while 13 neonates with early-onset disease were observed among those who did not receive IAP 5.
• The study also found that the incidence rate of early-onset disease was 6.06‰, with no statistically significant differences in incidence rates between the pandemic period and the following year 5.