What alternative antibiotics can be used to treat Group B Streptococcus (GBS) infection in a patient allergic to penicillin (PCN) and sulfa?

Alternative Antibiotics for Group B Streptococcus (GBS) in Patients with Penicillin and Sulfa Allergies

For patients with both penicillin and sulfa allergies, vancomycin is the recommended treatment for Group B Streptococcus infections when susceptibility testing is not available or when isolates are resistant to other antibiotics. 1

Assessment of Penicillin Allergy Severity

• Determine if the patient has a high risk for anaphylaxis (history of immediate hypersensitivity reactions like anaphylaxis, angioedema, urticaria, or history of asthma) 2
• Verification of reported penicillin allergy is important before selecting alternative antibiotics 2
• Approximately 10% of persons with penicillin allergy also have immediate hypersensitivity reactions to cephalosporins 2

Treatment Algorithm Based on Allergy Severity

For Non-Severe Penicillin Allergy (No History of Anaphylaxis):

• Cefazolin is the recommended alternative (2g IV initial dose, then 1g IV every 8 hours until treatment completion) 2
• GBS isolates remain highly susceptible to cefazolin with minimum inhibitory concentrations consistently low (<0.5 μg/ml) 2, 3

For Severe Penicillin Allergy (History of Anaphylaxis):

1. Obtain antimicrobial susceptibility testing for clindamycin and erythromycin if possible 2, 1
2. If isolate is susceptible to both clindamycin and erythromycin:
   • Clindamycin 900 mg IV every 8 hours 2, 1
3. If susceptibility testing is not available or isolate is resistant to clindamycin/erythromycin:
   • Vancomycin 1g IV every 12 hours 2, 1

Important Considerations and Caveats

• Resistance to clindamycin (11-28%) and erythromycin (16.7-30%) among GBS isolates has been increasing worldwide 3, 4
• The rate of co-resistance to clindamycin among erythromycin-resistant strains can be as high as 92% 4
• Erythromycin is no longer recommended for GBS infections due to increasing resistance 1, 5
• All GBS isolates remain universally susceptible to penicillin worldwide 5, 3
• Vancomycin should be reserved for cases where no other options exist due to concerns about promoting antimicrobial resistance 2, 1
• Susceptibility testing should always be performed when treating GBS infections in penicillin-allergic patients 1, 6

Clinical Pearls

• For patients with both penicillin and sulfa allergies, the treatment algorithm remains the same as for penicillin allergy alone 1
• Antibiotic susceptibility testing is crucial for guiding appropriate therapy in penicillin-allergic patients 6
• Consider consultation with an infectious disease specialist for complicated cases or when treatment options are limited 1
• While vancomycin remains largely effective against GBS, there have been rare documented cases of vancomycin resistance 5