What is the recommended treatment for Group B strep (Streptococcus agalactiae) vaginal colonization in pregnant women using Clindamycin?

Treatment of Group B Streptococcus Vaginal Colonization in Pregnant Women

For pregnant women with Group B Streptococcus (GBS) vaginal colonization who are allergic to penicillin, clindamycin 900mg IV every 8 hours until delivery is recommended only if the GBS isolate is tested and confirmed to be susceptible to clindamycin. 1

First-Line Treatment Options

For non-penicillin allergic pregnant women with GBS colonization, the recommended treatment regimens are:

• First choice: Penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery) 1
• Acceptable alternative: Ampicillin (2g IV initial dose, then 1g IV every 4 hours until delivery) 1

Treatment for Penicillin-Allergic Patients

Treatment selection depends on the severity of the penicillin allergy:

Patients WITHOUT history of anaphylaxis to penicillin:

• Recommended: Cefazolin 2g IV initial dose, then 1g IV every 8 hours until delivery 1

Patients WITH history of anaphylaxis to penicillin:

1. Test GBS isolate for susceptibility to clindamycin and erythromycin 2, 1
2. If susceptible to clindamycin: Clindamycin 900mg IV every 8 hours until delivery 1
3. If resistant to clindamycin OR susceptibility unknown: Vancomycin 1g IV every 12 hours until delivery 1

Important Considerations for Clindamycin Use

• Antimicrobial susceptibility testing is essential before using clindamycin due to increasing resistance rates 1
• Recent studies show clindamycin resistance rates of 14-26.6% among GBS isolates 3, 4
• Erythromycin resistance (which often correlates with clindamycin resistance) has been reported at 14.5-32.9% 3, 4
• Inducible resistance to clindamycin can occur in approximately 5.8-13.9% of isolates that appear susceptible to clindamycin but resistant to erythromycin 3, 4

Key Clinical Pearls

• Oral antibiotics in the third trimester are ineffective for treating GBS colonization; 30-70% of treated women remain colonized at delivery 1
• Vancomycin should be reserved only for cases where clindamycin cannot be used due to resistance or unknown susceptibility 2, 1
• Erythromycin is no longer recommended for GBS prophylaxis due to increasing resistance and poor placental transfer 1
• All GBS isolates remain susceptible to penicillin G 3, 4, making it the most reliable option for non-allergic patients

Timing and Screening

• GBS screening is recommended at 36 0/7 to 37 6/7 weeks of gestation (updated from previous 35-37 weeks recommendation) 5
• Intrapartum antibiotic prophylaxis is most effective when administered at least 4 hours before delivery 1
• For penicillin-allergic patients, consider skin testing as confirmation of or delabeling from penicillin allergy can provide both short- and long-term health benefits 5

Remember that the primary goal of treatment is to prevent early-onset GBS disease in the newborn, which can cause significant morbidity and mortality. Proper antibiotic selection based on maternal allergy history and GBS susceptibility testing is crucial for effective prevention while minimizing risks of antibiotic resistance and adverse reactions.