What is the recommended treatment for a 48-year-old menstruating female potential living kidney donor with a urine culture showing 50,000 CFU/mL Streptococcus agalactiae (Group B)?

Treatment of Asymptomatic Group B Streptococcus Bacteriuria in a Potential Kidney Donor

Treatment with oral penicillin or ampicillin for 5-7 days is recommended for this 48-year-old female with asymptomatic Group B Streptococcus (GBS) bacteriuria at 50,000 CFU/mL.

Assessment of the Clinical Scenario

This case involves a 48-year-old menstruating female being evaluated as a potential living kidney donor with:

• Normal urinalysis
• Urine culture showing 50,000 CFU/mL Streptococcus agalactiae (Group B)
• No reported symptoms of urinary tract infection

Treatment Recommendations

First-Line Treatment

• Oral penicillin V: 500 mg four times daily for 5-7 days 1 OR
• Oral ampicillin: 500 mg four times daily for 5-7 days 2

Alternative Options (for penicillin-allergic patients)

• For patients with non-severe penicillin allergy:
  • Cefazolin: 500 mg orally three times daily for 5-7 days 3
• For patients with severe penicillin allergy (history of anaphylaxis, angioedema, respiratory distress, or urticaria):
  • Susceptibility testing should be performed before prescribing alternatives 4
  • Clindamycin may be used if susceptibility is confirmed 4

Rationale for Treatment

1. Need for treatment: Although asymptomatic, treatment is warranted in this case because:

   • The patient is being evaluated as a potential kidney donor
   • GBS bacteriuria may represent a risk for ascending infection
   • Clearance of bacteriuria is important before donation evaluation proceeds

2. Antibiotic selection: Penicillin remains the agent of choice for GBS infections 3, 5

   • GBS remains universally susceptible to penicillin and other beta-lactams 5
   • As noted in the therapy note: "Penicillin resistance in beta hemolytic Strep. has not been reported"
   • Penicillin offers narrow-spectrum coverage appropriate for this organism

3. Duration of therapy: 5-7 days is recommended for uncomplicated UTIs 3

   • Longer duration (10-14 days) would be warranted only for complicated infections

Important Considerations

• Susceptibility testing: Not routinely needed for GBS as resistance to penicillin has not been reported 5

  • However, susceptibility testing should be ordered if the patient has a history of severe penicillin allergy 4

• Follow-up: A test of cure (repeat urine culture) should be performed 1-2 weeks after completing antibiotics to ensure eradication, especially important in the context of kidney donation evaluation

• Monitoring: Patients should be advised to complete the full course of antibiotics even if feeling well to prevent recurrence and development of resistance 1

Potential Pitfalls and Caveats

1. Distinguishing colonization from infection: In this case, the 50,000 CFU/mL count in a clean catch specimen from an asymptomatic individual could represent contamination or colonization. However, in the context of kidney donation evaluation, treatment is warranted regardless.

2. Antibiotic resistance concerns: While GBS remains susceptible to penicillin, increasing resistance to non-beta-lactam antibiotics including clindamycin, erythromycin, and fluoroquinolones has been observed 5. This underscores the importance of using penicillin as first-line when possible.

3. Oral absorption considerations: As noted in the penicillin drug label, "The oral route of administration should not be relied upon in patients with severe illness, or with nausea, vomiting, gastric dilatation, cardiospasm or intestinal hypermotility" 1. For this asymptomatic patient, oral therapy is appropriate.

4. Timing of administration: For maximal absorption, penicillin should be administered at least one half-hour before or two hours after meals 2.