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

Treatment of Group B Streptococcus (GBS) in Urine of Non-Pregnant Adults

Non-pregnant adults with Group B Streptococcus in urine should be treated according to standard urinary tract infection protocols with antibiotics to which GBS is susceptible, such as penicillin, ampicillin, or cephalosporins for symptomatic infections. While guidelines primarily focus on GBS in pregnancy, treatment principles can be applied to non-pregnant adults.

Diagnosis and Clinical Significance

• GBS accounts for approximately 2% of positive urine cultures in non-pregnant adults and should be considered a significant urinary pathogen 1
• The presence of GBS in urine may signal underlying urinary tract abnormalities, which are present in up to 60% of non-pregnant adults with GBS bacteriuria 1
• Clinical manifestations can affect both upper and lower urinary tract with similar frequency (37% and 38% of cases, respectively) 1

Antibiotic Selection for Treatment

• First-line treatment options include:

  • Penicillin G or ampicillin, as GBS remains universally susceptible to these agents 2
  • Cephalosporins (such as cefazolin or cephalothin) are excellent alternatives with high efficacy against GBS 2, 3

• For penicillin-allergic patients:

  • Patients without history of anaphylaxis: cefazolin is the preferred agent 4
  • Patients with history of anaphylaxis or severe reactions: vancomycin or clindamycin (if susceptibility confirmed) 4

Important Susceptibility Considerations

• All GBS isolates are typically susceptible to penicillin, ampicillin, cephalothin, and vancomycin 2
• Resistance to macrolides (erythromycin) has been increasing, from 8% to 18% in some studies, making these less reliable options 2, 4
• Clindamycin resistance is also increasing, necessitating susceptibility testing before use 4
• Testing for inducible clindamycin resistance should be performed on isolates that are susceptible to clindamycin but resistant to erythromycin 4

Treatment Duration and Approach

• Standard UTI treatment duration (typically 3-7 days for uncomplicated lower UTI, 7-14 days for complicated or upper UTI) should be followed 3
• For complicated cases with risk factors, consider longer treatment courses and follow-up cultures 1
• Treatment success depends on identifying and addressing potential reservoirs of infection outside the urinary tract 3

Risk Factors and Complications

• 95% of non-pregnant adults with GBS UTI have at least one underlying condition 1
• Common risk factors include:
  • Urinary tract abnormalities (60% of cases) 1
  • Chronic renal failure (27% of cases) 1
  • Liver disease (35.3% of bacteremic cases) 2
  • Malignancies (33.3% of bacteremic cases) 2
  • Diabetes mellitus (27.5% of bacteremic cases) 2
• Poor outcomes occur in approximately 18% of cases despite appropriate treatment 1

Monitoring and Follow-up

• Consider screening for underlying urinary tract abnormalities in patients with GBS UTI 1
• Follow-up cultures may be warranted to ensure eradication, especially in patients with structural abnormalities or recurrent infections 3
• Be vigilant for potential progression to invasive disease, particularly in elderly patients and those with chronic conditions 5

Pitfalls to Avoid

• Do not dismiss GBS as a contaminant in urine cultures of non-pregnant adults, as it represents a true pathogen requiring treatment 1
• Avoid empiric use of macrolides for penicillin-allergic patients without susceptibility testing due to increasing resistance 2
• Be aware that GBS bacteremia carries a high mortality rate (33.3%) in adults with underlying conditions 2