In a pregnant patient who is group B Streptococcus positive and allergic to clindamycin and cefazolin, should intrapartum prophylaxis be with vancomycin or gentamicin?

GBS Prophylaxis in Penicillin-Allergic Patients: Vancomycin vs Gentamicin

For a pregnant patient who is GBS-positive with documented allergies to both clindamycin and cefazolin, vancomycin 1 g IV every 12 hours until delivery is the definitive choice for intrapartum prophylaxis—gentamicin is not an appropriate alternative for GBS prophylaxis. 1

Why Vancomycin Is the Correct Answer

Vancomycin is specifically recommended by the CDC for penicillin-allergic women at high risk for anaphylaxis when clindamycin is not an option due to resistance or allergy. 1 Since your patient is allergic to clindamycin, this eliminates the preferred alternative for high-risk penicillin allergy, making vancomycin the appropriate choice. 1

The CDC guidelines explicitly state that vancomycin should be used when:

• The patient has a high-risk penicillin allergy (anaphylaxis, angioedema, respiratory distress, or urticaria), AND
• Clindamycin is not available due to resistance or allergy, AND
• Susceptibility testing is unavailable or shows resistance 1

Your patient meets these criteria with documented clindamycin allergy. 1

Why Gentamicin Is NOT Appropriate

Gentamicin is never recommended as monotherapy for GBS intrapartum prophylaxis in the CDC guidelines. 1 While gentamicin is mentioned in the guidelines, it appears only in the context of:

• Neonatal sepsis treatment (ampicillin plus gentamicin combination) 2, 3
• Broad-spectrum coverage for suspected chorioamnionitis 1

Gentamicin alone does not provide adequate GBS prophylaxis and is not part of the CDC algorithm for intrapartum GBS prevention. 1

The Complete CDC Algorithm for Your Patient

Since your patient has allergies to both cefazolin and clindamycin:

1. Cefazolin is excluded because the patient is allergic to it (cefazolin would normally be the choice for low-risk penicillin allergy) 1

2. Clindamycin is excluded because the patient is allergic to it (clindamycin would be the choice for high-risk allergy with susceptible isolates) 1

3. Vancomycin becomes the only remaining option per CDC guidelines: 1 g IV every 12 hours until delivery 1

Critical Clinical Considerations

The allergy to cefazolin suggests this patient likely has a high-risk penicillin allergy (since cefazolin is a cephalosporin with ~10% cross-reactivity in penicillin-allergic patients). 1 This further supports the use of vancomycin rather than attempting any beta-lactam agent. 1

Vancomycin should be reserved for situations exactly like this—when no other appropriate alternatives exist—to minimize promoting vancomycin resistance. 1 However, the CDC acknowledges that approximately 100,000 deliveries annually would require vancomycin prophylaxis when clindamycin/erythromycin are unavailable, representing less than 1% increase in total vancomycin use. 1

Common Pitfall to Avoid

Do not attempt to use gentamicin as a substitute for vancomycin in this scenario. 1 Gentamicin lacks adequate activity against GBS as monotherapy for prophylaxis and is not endorsed by any major guideline for this indication. 1, 2