Do we treat a urine culture showing 50,000-99,000 Colony-Forming Units per Milliliter (CFU/mL) of Group B Streptococcus (GBS) that is beta-hemolytic?

Management of Group B Streptococcus in Urine with Colony Count 50,000-99,000 CFU/mL

Women with Group B Streptococcus isolated from urine in any concentration during pregnancy should receive treatment for the current infection and intrapartum antibiotic prophylaxis due to their increased risk of delivering an infant with early-onset GBS disease. 1, 2

Diagnosis and Significance

• GBS bacteriuria during pregnancy is a marker for heavy genital tract colonization and significantly increases the risk for early-onset neonatal GBS disease 1, 2
• The CDC recommends that laboratories report GBS in urine culture specimens when present at concentrations of ≥10^4 colony-forming units/ml (which includes the 50,000-99,000 CFU/mL range in question) 2, 1
• A colony count of 50,000-99,000 CFU/mL falls within the reportable range and requires treatment 2, 1
• GBS bacteriuria at any point during pregnancy is a recognized risk factor for early-onset GBS disease 2

Treatment Approach

Current Infection Management

• Women with symptomatic or asymptomatic GBS urinary tract infection detected during pregnancy should be treated according to current standards of care for urinary tract infection 2, 1
• Treatment of the current GBS bacteriuria is necessary even though it does not eliminate the need for intrapartum prophylaxis 1
• Antibiotics given before the intrapartum period do not eliminate GBS from the genitourinary and gastrointestinal tracts, as recolonization after treatment is typical 2, 1

Intrapartum Management

• All women with documented GBS bacteriuria during the current pregnancy should receive intrapartum antibiotic prophylaxis regardless of the concentration of bacteria found in the urine 1, 3
• For intrapartum prophylaxis in women without penicillin allergy, the recommended regimen is: penicillin G, 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery 1, 2
• An alternative regimen is ampicillin, 2 g IV initial dose, then 1 g IV every 4 hours until delivery 1, 2

Special Considerations

Penicillin Allergy

• For women with penicillin allergy who are not at high risk for anaphylaxis: cefazolin, 2 g IV initial dose, then 1 g IV every 8 hours until delivery 1, 2
• For women at high risk for anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria following administration of penicillin or cephalosporin), susceptibility testing for clindamycin and erythromycin should be performed on GBS isolates 1, 2
• If the isolate is susceptible to clindamycin: administer clindamycin, 900 mg IV every 8 hours until delivery 1, 2

Additional Considerations

• Prenatal culture-based screening at 35-37 weeks' gestation is not necessary for women with GBS bacteriuria during the current pregnancy 2
• Women with GBS bacteriuria should not be re-screened by genital tract culture or urinary culture in the third trimester, as they are presumed to be GBS colonized 3
• Women with planned cesarean delivery performed before rupture of membranes and onset of labor are at low risk for having an infant with early-onset GBS disease and may not require intrapartum prophylaxis 1, 2

Potential Pitfalls and Caveats

• Failure to report GBS in urine specimens from pregnant women can lead to missed opportunities for intrapartum prophylaxis 1
• Urine specimens from pregnant patients should be clearly labeled to indicate pregnancy status to assist laboratory processing and appropriate reporting of results 1, 2
• Not treating GBS bacteriuria during pregnancy can lead to increased risk of pyelonephritis, chorioamnionitis, and neonatal GBS disease 1, 3