What are alternative treatments for a beta-hemolytic group B strep (GBS) urinary tract infection (UTI) in a patient with a penicillin allergy?

Treatment of Beta-Hemolytic Group B Strep UTI in Patients with Penicillin Allergy

For patients with beta-hemolytic Group B Streptococcus (GBS) urinary tract infections and penicillin allergy, vancomycin is the recommended first-line treatment when susceptibility testing is not available or pending. 1

Assessment of Penicillin Allergy Severity

• Determine if the patient has a severe penicillin allergy, defined as a history of anaphylaxis, angioedema, respiratory distress, or urticaria following administration of penicillin or cephalosporins 2, 1
• For patients without severe reactions (no history of anaphylaxis, angioedema, respiratory distress, or urticaria), cefazolin is the recommended alternative 2
• True penicillin allergy occurs in a smaller percentage of patients than reported, so verification of allergy history is important before selecting alternative antibiotics 2, 3

Treatment Algorithm Based on Allergy Severity

For Non-Severe Penicillin Allergy:

• First-line: Cefazolin (IV) 2, 1
  • Cross-reactivity between penicillins and cephalosporins occurs in approximately 10% of patients with penicillin allergy 2
  • GBS isolates remain highly susceptible to cefazolin 2

For Severe Penicillin Allergy:

• Obtain antimicrobial susceptibility testing for clindamycin and erythromycin if possible 2, 1
• If susceptibility testing is available:
  • For susceptible isolates: Clindamycin 900 mg IV every 8 hours 1
  • For resistant isolates: Vancomycin 1g IV every 12 hours 1
• If susceptibility testing is unavailable or pending: Vancomycin is the recommended empiric therapy 1

Important Considerations for Antimicrobial Selection

• Increasing resistance to clindamycin (up to 26%) and erythromycin (up to 44.5%) has been reported in GBS isolates 4, 5, 6
• A study from 1999 showed significant increase in resistance of GBS to both clindamycin and erythromycin compared to earlier periods 6
• All GBS isolates remain susceptible to penicillin worldwide 1
• Erythromycin is no longer recommended for GBS infections due to increasing resistance 1, 4
• Recent research (2023) confirms that despite clindamycin resistance in GBS, these isolates remain susceptible to penicillin, ampicillin, linezolid, vancomycin, tigecycline, and quinupristin-dalfopristin 5

Clinical Pearls and Pitfalls

• Always obtain susceptibility testing when treating GBS infections in penicillin-allergic patients to guide optimal therapy 1
• Consider infectious disease consultation for complicated cases or when treatment options are limited 1
• Do not use erythromycin for GBS infections due to high rates of resistance 1, 4
• For outpatient oral therapy in penicillin-allergic patients with susceptible isolates, clindamycin has shown efficacy in eradicating streptococcal carriage 7
• The CDC advises against using cefazolin in patients with severe penicillin allergy due to risk of cross-reactivity 1

Duration of Therapy

• Standard duration of therapy for uncomplicated UTI caused by GBS is typically 7-10 days, similar to other bacterial UTIs 1
• Longer courses may be needed for complicated infections or in patients with recurrent infections 1