Does a woman who grows Group B Streptococcus (GBS) in her urine always have a Group B Strep infection?

Group B Streptococcus in Urine During Pregnancy

No, a woman who grows Group B Streptococcus (GBS) in her urine does not always have a GBS infection, but the presence of GBS in urine at any concentration is considered a marker for heavy genital tract colonization rather than necessarily indicating a urinary tract infection. 1

Understanding GBS in Urine

Significance of GBS in Urine

• The presence of GBS in urine during pregnancy, regardless of colony count, indicates heavy genital tract colonization 1
• GBS can cause both symptomatic and asymptomatic urinary tract infections 1
• Laboratory personnel should report any presence of GBS bacteriuria in specimens from pregnant women 1

Colony Count Considerations

• Significant GBS bacteriuria is generally defined as >10⁵ colony-forming units per milliliter of urine 1
• Lower concentrations (<10⁴ CFU/ml) are also associated with vaginal-rectal colonization 1
• One study found that women with ≥10⁴ CFU GBS/ml urine had neonates who were more commonly and heavily colonized, suggesting higher risk for neonatal infection 2

Clinical Implications

Management During Pregnancy

• Women with GBS bacteriuria during pregnancy should receive intrapartum antibiotic prophylaxis (IAP) during labor, regardless of the colony count 1, 3
• Vaginal and rectal screening at 35-37 weeks is not necessary for women who have had GBS bacteriuria during the current pregnancy 1, 3
• Women with documented 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

Treatment Recommendations

• Treatment of bacteriuria with colony counts ≥100,000 CFU/mL in pregnancy is recommended with appropriate antibiotics 3
• Asymptomatic women with urinary GBS colony counts <100,000 CFU/mL should not be treated with antibiotics for prevention of adverse outcomes such as pyelonephritis, chorioamnionitis, or preterm birth 3
• However, all women with documented GBS bacteriuria (regardless of level of colony-forming units) in the current pregnancy should receive IAP during labor 3, 4

Important Distinctions

Colonization vs. Infection

• GBS is a common commensal in the genitourinary and gastrointestinal tracts, found in approximately 20% of women globally 5
• Asymptomatic GBS colonization generally does not require treatment outside of pregnancy 6
• The gastrointestinal tract is considered the main habitat of GBS, with GBS detected more often in rectal specimens than in urethral or urine specimens 2

Pitfalls to Avoid

• Do not confuse GBS colonization with active infection requiring immediate treatment outside of labor
• Do not assume that a cesarean delivery eliminates the need for IAP in women with GBS bacteriuria, as GBS can cross intact amniotic membranes 1
• Avoid unnecessary antibiotic treatment for asymptomatic low-colony-count bacteriuria outside of labor, as this may contribute to antibiotic resistance 3

In summary, while the presence of GBS in urine does not always indicate an active infection requiring immediate treatment, it does signify colonization that warrants intrapartum antibiotic prophylaxis during labor to prevent early-onset neonatal GBS disease.