What is the treatment for Group B strep (Streptococcus agalactiae) vaginal infection in a non-pregnant individual allergic to penicillin (PCN)?

Treatment for Group B Strep Vaginal Infection in Non-Pregnant Individuals with Penicillin Allergy

For non-pregnant individuals with Group B streptococcal (GBS) vaginal infection who are allergic to penicillin, clindamycin 300-450mg orally 3-4 times daily for 7-14 days is recommended if susceptibility testing confirms the isolate is sensitive to clindamycin. 1

Assessment of Penicillin Allergy Severity

The treatment approach depends on the severity of the penicillin allergy:

Low-Risk for Anaphylaxis

• Patients without history of immediate hypersensitivity reactions (anaphylaxis, angioedema, respiratory distress, or urticaria)
• Recommended treatment: Cefazolin or appropriate oral cephalosporin 2, 1
  • Cross-reactivity between penicillins and cephalosporins occurs in only about 10% of patients 1

High-Risk for Anaphylaxis

• Patients with history of anaphylaxis, angioedema, respiratory distress, or urticaria following penicillin administration
• Recommended treatment options:
  1. Clindamycin (if susceptible): 300-450mg orally 3-4 times daily 1
  2. Vancomycin (if clindamycin resistance or unknown susceptibility): 1g IV every 12 hours 2, 1

Importance of Susceptibility Testing

• Approximately 20% of GBS isolates are resistant to clindamycin 1
• Erythromycin is no longer recommended due to high resistance rates 2, 1
• The D-zone test is required to detect inducible clindamycin resistance if the isolate is erythromycin-resistant but clindamycin-susceptible 1
• Susceptibility testing should be performed before initiating treatment 1, 3

Treatment Duration and Follow-up

• Treatment duration: 7-14 days depending on clinical response and severity 1
• Follow-up culture should be obtained after treatment completion to confirm eradication 1

Common Pitfalls to Avoid

1. Using erythromycin without susceptibility testing: Erythromycin is no longer an acceptable alternative due to high resistance rates 2, 1

2. Assuming cross-reactivity between penicillins and cephalosporins: While cross-reactivity exists, it occurs in only about 10% of patients. However, patients with high-risk penicillin allergy should still avoid cephalosporins 1

3. Failure to perform susceptibility testing: Due to increasing resistance patterns, susceptibility testing is crucial before using clindamycin 1, 4, 5

4. Not confirming eradication: Follow-up culture should be obtained after treatment completion to confirm eradication 1

By following this treatment algorithm based on allergy severity and susceptibility testing, clinicians can effectively treat GBS vaginal infections in non-pregnant individuals with penicillin allergy while minimizing risks of treatment failure or adverse reactions.