What is the recommended oral therapy for a non-pregnant adult with Group B streptococcus (GBS) in their urine?

Oral Therapy for Group B Streptococcus (GBS) in Urine for Non-Pregnant Adults

For non-pregnant adults with Group B streptococcus (GBS) in their urine, penicillin is the recommended first-line oral therapy due to its narrow spectrum of activity and effectiveness against GBS. While the CDC guidelines primarily focus on GBS in pregnant women, the same antimicrobial susceptibility principles apply to non-pregnant adults.

First-Line Treatment Options

• Penicillin V (oral) is the preferred first-line agent due to its narrow spectrum of activity, which reduces the risk of selecting for antibiotic-resistant organisms 1.

• Amoxicillin (oral) is an acceptable alternative to penicillin with similar efficacy against GBS 1.

Treatment for Penicillin-Allergic Patients

Treatment should be guided by the severity of penicillin allergy and antimicrobial susceptibility testing:

• For patients with non-severe penicillin allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):

  • Cephalexin (oral first-generation cephalosporin) is recommended 1.

• For patients with severe penicillin allergy (history of anaphylaxis, angioedema, respiratory distress, or urticaria):

  • Clindamycin is recommended if the GBS isolate is confirmed susceptible 1.
  • Alternative: Linezolid may be considered for multi-drug resistant strains 2.

Antimicrobial Susceptibility Testing

• Susceptibility testing should be performed on GBS isolates from penicillin-allergic patients at high risk for anaphylaxis 1.

• Testing for inducible clindamycin resistance should be performed on isolates that are susceptible to clindamycin but resistant to erythromycin 1.

Important Considerations

• GBS in urine should be treated regardless of colony count when found in pure culture or mixed with a second microorganism at concentrations of ≥10⁴ colony-forming units/ml 1, 3.

• Duration of therapy: Standard course of 7-10 days for uncomplicated urinary tract infections 4.

• Oral step-down therapy has been shown to be effective for uncomplicated streptococcal infections after initial clinical improvement, which may be applicable to urinary GBS infections 4.

Monitoring and Follow-up

• Consider follow-up urine culture after completion of therapy to confirm eradication, especially in patients with recurrent UTIs 3.

• For complicated cases or treatment failures, consider urologic evaluation to rule out structural abnormalities 3.

Emerging Resistance Concerns

• While GBS remains largely susceptible to beta-lactams, there have been reports of reduced susceptibility to penicillins in some countries 2.

• Resistance to second-line antibiotics such as erythromycin and clindamycin is increasing globally, necessitating susceptibility testing before their use 2.

Common Pitfalls to Avoid

• Do not use erythromycin empirically without susceptibility testing due to high rates of resistance 1, 2.

• Do not confuse treatment approaches for pregnant vs. non-pregnant patients. While the principles are similar, the implications and urgency differ 1, 3.

• Do not neglect susceptibility testing in penicillin-allergic patients, as resistance patterns to alternative antibiotics are increasing 1, 2.