Should a urine sample positive for group B streptococcus (GBS) be treated with antibiotics?

Management of Group B Streptococcus in Urine Samples

Group B Streptococcus (GBS) detected in urine samples should be treated with antibiotics regardless of colony count, particularly in pregnant women, as it represents heavy genital tract colonization and increases risk for complications. 1, 2

Treatment Algorithm for GBS in Urine

For Pregnant Women

1. Immediate Treatment Required

   • Treat any concentration of GBS in urine during pregnancy 1, 2
   • GBS bacteriuria is a marker for heavy genital tract colonization 1
   • Treatment is necessary regardless of symptoms (symptomatic or asymptomatic) 1

2. Antibiotic Selection

   • First-line: Penicillin G or Ampicillin 2
   • Alternative for penicillin-allergic patients: Nitrofurantoin for lower UTIs 2, 3
   • For penicillin-allergic patients with severe reactions: Cefazolin, clindamycin, or vancomycin 2

3. Follow-up Care

   • Follow-up urine culture after treatment completion 2
   • Intrapartum antibiotic prophylaxis will be needed during labor 1, 2
   • No need for vaginal and rectal screening at 35-37 weeks if GBS bacteriuria was detected earlier in pregnancy 1

For Non-Pregnant Adults

• Treatment is indicated, especially with symptoms of UTI 4
• First-line options include penicillin G, ampicillin, or nitrofurantoin 2, 3
• Consider screening for urinary tract abnormalities, as 60% of non-pregnant adults with GBS UTI have underlying urinary tract issues 4

Clinical Considerations

Colony Count Significance

• The CDC guidelines recommend reporting and treating GBS in urine at concentrations of ≥10^4 colony-forming units/ml 2
• However, earlier guidelines suggested treating any quantity of GBS bacteriuria in pregnant women 1
• Low colony counts (<10^4 CFU/ml) of GBS can still indicate vaginal-rectal colonization 1

Antibiotic Resistance Patterns

• All GBS isolates in studies remain sensitive to penicillin, ampicillin, and nitrofurantoin 3
• However, some isolates (15-17%) may show intermediate or decreased sensitivity to penicillin and ampicillin 3
• For patients with penicillin allergy, antibiotic sensitivity testing is recommended 3

Potential Benefits Beyond UTI Treatment

• In pregnant women, treating GBS bacteriuria may reduce rates of:
  • Premature rupture of membranes (11% vs 53% in treated vs untreated) 5
  • Preterm labor (5.4% vs 38% in treated vs untreated) 5
  • Early-onset neonatal GBS disease 1

Pitfalls to Avoid

1. Not treating low colony counts: Even low concentrations of GBS in urine can indicate heavy genital tract colonization 1
2. Missing GBS in urine: Proper labeling of urine specimens from pregnant women is crucial for laboratory identification 1
3. Failing to provide intrapartum prophylaxis: Women with GBS bacteriuria during pregnancy need intrapartum antibiotics regardless of whether they received treatment earlier in pregnancy 1, 2
4. Not considering antibiotic resistance: For penicillin-allergic patients, sensitivity testing should guide antibiotic selection 3
5. Overlooking underlying conditions: In non-pregnant adults with GBS UTI, consider screening for urinary tract abnormalities 4

By following these guidelines, clinicians can effectively manage GBS detected in urine samples and reduce the risk of associated complications, particularly in pregnant women.