What is the management for a patient with Group B streptococcus (Strep B) on urine culture, particularly in pregnant women or those with underlying medical conditions?

Management of Group B Streptococcus on Urine Culture

The management of GBS bacteriuria depends entirely on pregnancy status: pregnant women require immediate treatment of symptomatic UTI plus mandatory intrapartum IV antibiotic prophylaxis during labor regardless of colony count or prior treatment, while non-pregnant adults should only be treated if symptomatic or if underlying urinary tract abnormalities are present. 1

For Pregnant Women

Immediate Actions Required

• Treat any symptomatic UTI immediately according to standard pregnancy UTI protocols using pregnancy-safe antibiotics based on susceptibility testing 1
• Document the GBS bacteriuria in the prenatal record and communicate to the anticipated site of delivery 1
• Do NOT perform vaginal-rectal screening at 35-37 weeks - women with GBS bacteriuria at any point in pregnancy are presumed heavily colonized and automatically qualify for intrapartum prophylaxis 1

Critical Concept: Why Treatment Alone Is Insufficient

Treating the UTI during pregnancy does NOT eliminate GBS colonization from the genitourinary tract - recolonization after oral antibiotics is typical, which is why intrapartum IV prophylaxis remains mandatory even if bacteriuria was treated earlier in pregnancy 1. GBS bacteriuria at any concentration is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease 2, 1.

Intrapartum Prophylaxis Regimens (During Labor)

First-line for patients without penicillin allergy:

• Penicillin G 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery (preferred agent due to narrow spectrum and universal GBS susceptibility) 1
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery 1

For penicillin-allergic patients NOT at high risk for anaphylaxis:

• Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery 1

For penicillin-allergic patients at HIGH risk for anaphylaxis (history of immediate hypersensitivity reactions including anaphylaxis, angioedema, urticaria, or history of asthma):

• Clindamycin 900 mg IV every 8 hours until delivery IF the isolate is confirmed susceptible to both clindamycin and erythromycin 1
• Vancomycin 1 g IV every 12 hours until delivery if susceptibility is unknown or the isolate is resistant to clindamycin 1
• Susceptibility testing for clindamycin and erythromycin must be performed immediately for high-risk allergy patients, as clindamycin resistance ranges from 3-15% among GBS isolates 1

Timing and Effectiveness

• Intrapartum prophylaxis must be administered ≥4 hours before delivery for maximum effectiveness 1
• When given ≥4 hours before delivery, prophylaxis is 78% effective in preventing early-onset neonatal GBS disease 2, 1

Special Pregnancy Scenarios

Preterm labor (<37 weeks):

• Women admitted with signs and symptoms of preterm labor with GBS bacteriuria should receive GBS prophylaxis immediately at hospital admission 1

Preterm premature rupture of membranes (PPROM) at ≥24 weeks:

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours is adequate for both latency prolongation and GBS prophylaxis 1

Cesarean delivery before labor onset with intact membranes:

• Intrapartum antibiotic prophylaxis is NOT routinely indicated regardless of GBS status 2

For Non-Pregnant Adults

Treatment Indications

Treat ONLY if:

• Patient is symptomatic (dysuria, frequency, urgency, suprapubic pain, fever) 3, 4
• Underlying urinary tract abnormalities are present 3, 4

Do NOT treat if:

• Patient is asymptomatic with normal urinalysis - this represents asymptomatic bacteriuria that should not be treated 3
• The 2019 IDSA guidelines provide strong evidence against screening for or treating asymptomatic bacteriuria in non-pregnant populations 3

Treatment Regimens for Symptomatic Non-Pregnant Patients

First-line:

• Penicillin G 500 mg orally every 6-8 hours for 7-10 days (preferred due to narrow spectrum) 3
• Alternative: Ampicillin 500 mg orally every 8 hours for 7-10 days 3

For penicillin-allergic patients:

• Clindamycin 300-450 mg orally every 8 hours for 7-10 days (requires susceptibility testing due to increasing resistance) 3

For complicated infections or when prostatitis cannot be excluded in men:

• Extend treatment to 14 days 3
• Consider initial IV therapy with ampicillin 2 g IV every 4-6 hours, then transition to oral therapy once clinically stable 3

Common Pitfalls to Avoid

• Never use oral or IV antibiotics before labor to treat asymptomatic GBS colonization in pregnancy - such treatment is completely ineffective at eliminating carriage and may cause adverse consequences including antibiotic resistance 1
• Do not assume that treating a GBS UTI in pregnancy eliminates the need for intrapartum prophylaxis - this is a common and dangerous error 1
• Do not treat asymptomatic bacteriuria in non-pregnant patients - this leads to unnecessary antibiotic exposure, resistance development, and potential adverse drug effects without clinical benefit 3
• Approximately 10% of persons with penicillin allergy also have immediate hypersensitivity reactions to cephalosporins, making risk assessment essential before using cefazolin 1

Laboratory Considerations

• Laboratories should report GBS present at ≥10,000 CFU/mL (≥10⁴ CFU/mL) as the threshold for clinical significance in pregnancy 1
• Urine specimen labels from prenatal patients must clearly state pregnancy status to ensure proper laboratory processing and reporting 4
• For high-risk penicillin allergy patients, susceptibility testing including D-zone testing should be performed on isolates that are erythromycin-resistant but clindamycin-susceptible to detect inducible clindamycin resistance 1