What is the appropriate treatment for a postpartum woman diagnosed with Group B streptococcus endometritis, considering potential allergies and underlying health conditions?

Group B Streptococcus Endometritis

First-Line Treatment

For postpartum endometritis caused by Group B Streptococcus, initiate intravenous ampicillin 2 g every 6 hours or penicillin G 5 million units initially followed by 2.5 million units every 4 hours, as these beta-lactam antibiotics provide narrow-spectrum coverage with universal GBS susceptibility. 1

• Ampicillin is the preferred agent for postpartum endometritis because it covers the polymicrobial nature of this infection, which commonly includes GBS along with other facultative and anaerobic bacteria 2
• Penicillin G remains highly effective as GBS isolates have demonstrated universal susceptibility to penicillin worldwide with no confirmed resistance reported to date 1
• Treatment should continue for at least 48-72 hours after the patient becomes afebrile and asymptomatic 3, 4

Treatment for Penicillin-Allergic Patients

The approach to penicillin allergy must be stratified by anaphylaxis risk, as approximately 10% of penicillin-allergic patients also react to cephalosporins. 5

For Non-High-Risk Allergy (no history of anaphylaxis, angioedema, or urticaria):

• Cefazolin 2 g IV initially, then 1 g IV every 8 hours is the preferred alternative 5
• First-generation cephalosporins like cefazolin are safe in this population and maintain excellent GBS coverage 1

For High-Risk Allergy (history of immediate hypersensitivity reactions):

• Clindamycin 900 mg IV every 8 hours only if susceptibility testing confirms the isolate is susceptible 5, 6
• Vancomycin 1 g IV every 12 hours if clindamycin resistance is documented or susceptibility testing is unavailable 5
• Critical caveat: Clindamycin resistance among GBS isolates ranges from 3-15%, and erythromycin resistance ranges from 7-21%, making susceptibility testing mandatory before using clindamycin 1, 5

Polymicrobial Nature of Postpartum Endometritis

Postpartum endometritis is typically polymicrobial, with GBS present alongside other organisms in the majority of cases. 2

• At least one facultative or anaerobic bacterial species is recovered from 82% of endometritis cases, with genital mycoplasmas present in 76% 2
• Common co-pathogens include Gardnerella vaginalis, Peptococcus spp., Bacteroides spp., Staphylococcus epidermidis, and Ureaplasma urealyticum 2
• This polymicrobial etiology explains why ampicillin (with broader spectrum than penicillin G) is often preferred for postpartum endometritis despite penicillin's narrower spectrum being ideal for isolated GBS 2

Risk Factors and Clinical Context

GBS colonization significantly increases the risk of maternal peripartum complications, with heavy colonization doubling the risk of intra-amniotic infection. 7

• Women with heavy GBS vaginal colonization have a 2-fold increased risk of intra-amniotic infection (OR 2.0,95% CI 1.1-3.7) compared to non-colonized women 7
• GBS-associated postpartum endometritis risk is elevated regardless of colonization density (OR 1.8,95% CI 1.3-2.7) 7
• The association between abdominal delivery, endometritis, and puerperal sepsis is particularly striking, with an attack rate of 2 per 1,000 deliveries for GBS puerperal sepsis 8

Critical Clinical Pitfalls

Never attempt to treat GBS colonization with oral antibiotics before labor, as this approach is completely ineffective and may promote antibiotic resistance. 1, 5

• Antimicrobial agents administered before the intrapartum period do not eliminate GBS carriage or prevent neonatal disease 1
• Recolonization after oral antibiotics is typical, making prenatal treatment futile 5
• The only effective prevention strategy is intrapartum IV antibiotic prophylaxis administered during active labor 1

Do not underdose or prematurely discontinue therapy, as this leads to treatment failure and potential complications including sepsis and meningitis. 5, 9

• Postpartum GBS infections can progress to serious complications including bacteremia, sepsis, meningitis, and wound infections 9
• Treatment duration should be guided by clinical response, with continuation for at least 48-72 hours after symptom resolution 3, 4

Special Considerations for Future Pregnancies

Any woman with GBS bacteriuria or documented GBS infection during pregnancy automatically qualifies for intrapartum antibiotic prophylaxis in future pregnancies. 1, 5

• Women with previous GBS bacteriuria during pregnancy should receive intrapartum prophylaxis during subsequent labors 1, 5
• GBS bacteriuria at any concentration indicates heavy genital tract colonization and significantly increases risk of early-onset neonatal disease 5, 10
• These women do not require repeat vaginal-rectal screening cultures at 35-37 weeks gestation in future pregnancies 1, 5