Treatment of Group B Streptococcus in Urine Culture
Direct Answer
Yes, treat GBS bacteriuria in pregnant women at any concentration with intrapartum antibiotic prophylaxis during labor; for non-pregnant adults, treat only if symptomatic or if underlying urinary tract abnormalities are present. 1, 2
For Pregnant Women
Mandatory Treatment Approach
All pregnant women with GBS isolated from urine at any concentration during pregnancy must receive intrapartum antibiotic prophylaxis during labor. 1 This is a critical CDC guideline that supersedes typical UTI treatment thresholds because:
- GBS bacteriuria indicates heavy colonization and significantly increases risk of early-onset neonatal GBS disease 1
- The standard ≥10⁵ CFU/mL threshold does not apply—any detectable concentration warrants prophylaxis 1
- Prenatal culture-based screening at 35-37 weeks is not necessary for these women since they already qualify for prophylaxis 1
Treatment Timing and Agents
Symptomatic GBS UTI during pregnancy should be treated immediately according to standard UTI protocols, but intrapartum prophylaxis is still required during labor regardless of prior treatment. 1
- First-line: Penicillin G remains the preferred intrapartum prophylaxis agent 1, 3
- Alternative: Ampicillin is acceptable 1, 3
- Penicillin allergy (not high-risk for anaphylaxis): Cefazolin or cephalexin 3
- Penicillin allergy (high-risk for anaphylaxis): Clindamycin if susceptible, or vancomycin 3
Critical Caveat
Do not use antibiotics before the intrapartum period to treat asymptomatic GBS colonization—only treat symptomatic UTI or provide prophylaxis during labor. 1, 3 Prenatal antibiotic treatment does not eliminate colonization and may promote resistance 1
For Non-Pregnant Adults
Context-Dependent Treatment
Non-pregnant adults with GBS bacteriuria should be treated only if they are symptomatic or have underlying urinary tract abnormalities. 2 This represents a fundamental departure from pregnancy management:
- The CDC pregnancy guidelines mandating universal treatment do not apply to non-pregnant patients 2
- GBS accounts for approximately 2% of UTIs in non-pregnant adults, predominantly in women (85%) 4
- 95% of non-pregnant adults with GBS UTI have underlying conditions, most commonly urinary tract abnormalities (60%) or chronic renal failure (27%) 4
When to Treat Non-Pregnant Patients
Treat if any of the following are present:
- Symptomatic UTI: Dysuria, frequency, urgency, flank pain, fever 2, 4
- Urinary tract abnormalities: Structural abnormalities, neurogenic bladder, indwelling catheters 2, 4
- Recurrent UTIs: History of multiple infections 4
Treatment Regimens for Non-Pregnant Adults
Penicillin G 500 mg orally every 6-8 hours for 7-10 days is preferred due to narrow spectrum activity. 2, 3
- Alternative: Ampicillin 500 mg orally every 8 hours for 7-10 days 2
- Penicillin allergy: Clindamycin 300-450 mg orally every 8 hours (requires susceptibility testing) 2
- Alternative for bacteriuria: Nitrofurantoin (all isolates in one study were sensitive) 5
Important Screening Consideration
The presence of GBS bacteriuria in non-pregnant adults should prompt evaluation for underlying urinary tract abnormalities, as 60% have structural problems. 4
Laboratory Considerations
Reporting Standards
Laboratories should report GBS in urine when present at concentrations ≥10⁴ CFU/mL in pure culture or mixed with a second organism for non-pregnant patients. 1 However, for pregnant women, any concentration is clinically significant 1
Urine specimen labels from prenatal patients must clearly state pregnancy status to ensure proper laboratory processing and reporting. 1
Susceptibility Testing Requirements
Perform antimicrobial susceptibility testing on GBS isolates from penicillin-allergic patients at high risk for anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria after penicillin/cephalosporin). 1, 3
- Test for inducible clindamycin resistance on isolates susceptible to clindamycin but resistant to erythromycin 1, 3
- Approximately 20% of GBS isolates are resistant to clindamycin 3
- All isolates remain sensitive to penicillin and vancomycin, though some show intermediate sensitivity to ampicillin (17%) and penicillin (15%) 5
Common Pitfalls to Avoid
Do not treat asymptomatic GBS bacteriuria in non-pregnant adults—this differs fundamentally from pregnancy management and promotes unnecessary antibiotic resistance. 2
Do not assume prenatal antibiotic treatment of GBS UTI eliminates the need for intrapartum prophylaxis—prophylaxis during labor is still mandatory. 1
Do not use ampicillin empirically for UTI in pregnancy without culture—resistance rates to E. coli are high, though GBS remains sensitive. 6
Do not fail to complete the full antibiotic course—premature discontinuation leads to treatment failure and recurrence. 3