Treatment of Streptococcus agalactiae (GBS) Found in Urine
Critical First Distinction: Pregnancy Status Determines Everything
The treatment approach for GBS bacteriuria depends entirely on whether the patient is pregnant—pregnant women require intrapartum antibiotic prophylaxis regardless of symptoms or colony count, while non-pregnant patients should only be treated if symptomatic or have underlying urinary tract abnormalities. 1, 2, 3
For Pregnant Women
Mandatory Treatment Indication
- Any concentration of GBS in urine at any point during pregnancy mandates intrapartum antibiotic prophylaxis during labor, regardless of colony count (even <10⁴ cfu/mL). 1, 3
- GBS bacteriuria is a marker for heavy genital tract colonization and significantly increases risk for early-onset neonatal disease. 1
- No vaginal-rectal screening at 35-37 weeks is needed if GBS bacteriuria has been documented at any point in the current pregnancy. 1
Treatment Protocol for Pregnant Women
- If symptomatic UTI: Treat the acute infection immediately with standard UTI antibiotics, PLUS provide intrapartum prophylaxis during labor. 1, 3
- If asymptomatic bacteriuria: Do NOT treat during pregnancy (antibiotics do not eliminate GBS from genitourinary/gastrointestinal tracts and recolonization is typical), but DO provide intrapartum prophylaxis. 1
Intrapartum Prophylaxis Regimen
- Penicillin G: 5 million units IV initially, then 2.5-3 million units IV every 4 hours until delivery (preferred agent). 3, 4
- Ampicillin: Acceptable alternative at 2 grams IV initially, then 1 gram IV every 4 hours until delivery. 3
- For penicillin allergy: Clindamycin 900 mg IV every 8 hours (requires susceptibility testing—approximately 20% of GBS isolates are resistant). 3, 5, 6
- Prophylaxis must be administered ≥4 hours before delivery to achieve 78% effectiveness in preventing early-onset neonatal GBS disease. 1, 3
For Non-Pregnant Patients
Treatment Indications (Symptomatic Only)
- Treat only if the patient has symptoms of UTI (dysuria, frequency, urgency, suprapubic pain) OR underlying urinary tract abnormalities. 2, 3
- Do NOT treat asymptomatic bacteriuria in non-pregnant patients—this promotes antibiotic resistance without clinical benefit. 2, 3
Antibiotic Regimens for Symptomatic Non-Pregnant Patients
- Penicillin G: 500 mg orally every 6-8 hours for 7-10 days (preferred due to narrow spectrum). 2, 3
- Ampicillin: 500 mg orally every 8 hours for 7-10 days (acceptable alternative). 2, 3, 7
- For penicillin allergy: Clindamycin 300-450 mg orally every 8 hours for 7-10 days (requires susceptibility testing due to resistance rates of 12-20%). 2, 5, 6
- For severe infections requiring IV therapy: Penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours. 3, 4
Antibiotic Susceptibility Considerations
- GBS shows >95% susceptibility to penicillin, ampicillin, cephalosporins, and vancomycin. 7, 6
- Clindamycin resistance is increasing (12-20% of isolates), making susceptibility testing mandatory before use. 3, 5, 6
- Erythromycin resistance occurs in approximately 13% of isolates, often mediated by erm(B) genes. 5, 6
Critical Pitfalls to Avoid
- Never treat asymptomatic GBS bacteriuria in non-pregnant patients—this is unnecessary and promotes resistance. 2, 3
- Never fail to provide intrapartum prophylaxis to pregnant women with any documented GBS bacteriuria—this increases neonatal mortality risk. 1, 3
- Never use clindamycin without susceptibility testing—resistance rates are too high to use empirically. 3, 5, 6
- Never underdose or prematurely discontinue antibiotics in symptomatic patients—this leads to treatment failure and recurrence. 3
- Never assume prenatal antibiotic treatment eliminates GBS colonization in pregnant women—recolonization is typical, and intrapartum prophylaxis is still required. 1
Follow-Up Considerations
- For non-pregnant patients with recurrent UTIs: Consider follow-up urine culture after treatment completion to ensure eradication. 2
- For pregnant women: No follow-up cultures are needed after documenting GBS bacteriuria—proceed directly to intrapartum prophylaxis during labor. 1
- Identify potential reservoirs (vagina, urethra, gastrointestinal tract) in patients with recurrent infections, particularly non-pregnant women. 7, 8