What is the treatment for a man with 10,000 to 50,000 CFU of Group B streptococcus (GBS) in his urine?

Treatment of Group B Streptococcus (GBS) in Male Urinary Tract

For a man with 10,000-50,000 CFU/ml of Group B Streptococcus in urine, ampicillin 500 mg four times daily for 7-10 days is the recommended treatment if the patient is symptomatic.

Determining Clinical Significance

• Colony counts of 10,000-50,000 CFU/ml fall below the traditional threshold (≥100,000 CFU/ml) for defining significant bacteriuria in men, making it important to correlate with symptoms before initiating treatment 1
• GBS in urine can represent true infection or contamination - one study found that even with counts ≥100,000 CFU/ml, one-third of patients had contaminated samples rather than true bacteriuria 2
• Asymptomatic bacteriuria in men is defined as a single voided urine specimen with one bacterial species isolated in a quantitative count ≥105 CFU/ml 1

Treatment Algorithm

Step 1: Assess for symptoms

• If symptomatic (dysuria, frequency, urgency, suprapubic pain):
  • Treat as a true infection 3
• If asymptomatic:
  • Do not treat unless patient falls into specific high-risk categories 4

Step 2: Evaluate for complicating factors

• Presence of urinary tract abnormalities (present in 60% of GBS UTI cases) 5
• History of chronic renal failure (present in 27% of GBS UTI cases) 5
• Immunocompromised status 3
• Recent urological procedure 3

Step 3: Treatment for symptomatic infection

• First-line treatment: Ampicillin 500 mg four times daily for 7-10 days 6, 7
• For severe or chronic infections, larger doses may be required 6
• For complicated infections with systemic symptoms, consider:
  • Ampicillin plus an aminoglycoside 6
  • Alternative: Cephalosporin 3

Special Considerations

• GBS isolates from urinary tract infections are typically sensitive to ampicillin and most other commonly used antibiotics 5
• For patients with penicillin allergy, cephalosporins are generally effective against GBS 3
• In cases of complicated UTI with GBS, treatment duration should be extended to 10-14 days 6

Monitoring and Follow-up

• For chronic urinary tract infections, frequent bacteriologic and clinical appraisal is necessary during therapy and may be necessary for several months afterwards 6
• Follow-up cultures should be obtained from the original site of infection 7 to 14 days after therapy 6
• Stubborn infections may require treatment for several weeks 6

Common Pitfalls to Avoid

• Treating asymptomatic bacteriuria unnecessarily can lead to antimicrobial resistance and eradication of potentially protective bacterial strains 4
• Undertreatment of GBS UTI can lead to persistent infection, as GBS has been shown to cause true urinary tract infections in both men and women 7, 2
• Failing to evaluate for underlying urological abnormalities, which are common in patients with GBS UTI 5