Streptococcus agalactiae (Group B Streptococcus) as a Cause of UTI
Yes, Streptococcus agalactiae definitively causes urinary tract infections in both pregnant and non-pregnant individuals, though it accounts for a relatively small proportion of UTIs overall.
Epidemiology and Clinical Significance
GBS causes 2-4% of urinary tract infections during pregnancy and represents a clinically important pathogen due to its association with heavy genital tract colonization and increased risk of neonatal disease 1. In non-pregnant populations, GBS accounts for approximately 1.79-8.92% of positive urine cultures in women, with higher prevalence in specific age groups (particularly 21-30 and 51-60 years) 2, 3.
Key Populations Affected
- Pregnant women: GBS bacteriuria occurs in 2-7% of pregnancies and serves as a marker for heavy genital tract colonization 1
- Non-pregnant adults: GBS causes UTIs in males and non-pregnant females, particularly those with underlying conditions such as diabetes mellitus 1, 4
- Elderly individuals: Increased susceptibility to GBS urinary tract infections, including asymptomatic bacteriuria 5
Clinical Manifestations
The spectrum of GBS urinary tract infections includes 1:
- Cystitis (most common presentation)
- Pyelonephritis
- Urosepsis
- Asymptomatic bacteriuria (particularly in elderly patients)
- Rare complications: Secondary abscess formation, though this is exceptionally uncommon 5
Genitourinary Reservoir
The gastrointestinal tract serves as the natural reservoir for GBS, with the genitourinary tract representing the most common site of secondary spread 1. This colonization pattern explains why 10-30% of pregnant women are colonized with GBS in the vaginal or rectal area 1.
Critical Management Distinctions
In Pregnant Women
Any quantity of GBS bacteriuria detected during pregnancy mandates both immediate treatment and intrapartum antibiotic prophylaxis, regardless of symptoms or colony count 1. This is because:
- GBS bacteriuria is a marker for heavy genital tract colonization 1
- It is associated with increased risk of early-onset neonatal GBS disease 1, 6
- Vaginal-rectal screening at 35-37 weeks is not necessary for women with documented GBS bacteriuria 1
In Non-Pregnant Patients
Treatment should only be provided for symptomatic UTI or in patients with underlying urinary tract abnormalities 7. Asymptomatic bacteriuria with GBS in non-pregnant patients should NOT be treated, as this leads to unnecessary antibiotic exposure and resistance development without clinical benefit 7.
Common Pitfalls to Avoid
Do not extrapolate pregnancy guidelines to non-pregnant patients: The CDC mandate to treat all GBS bacteriuria applies specifically to pregnant women to prevent neonatal disease and should not be applied to non-pregnant individuals 7. This is a critical distinction that prevents unnecessary antibiotic use.
Do not assume all GBS in urine requires treatment: In non-pregnant patients with normal urinalysis and no genitourinary symptoms, GBS represents asymptomatic bacteriuria that should be left untreated per IDSA guidelines 7.
Antibiotic Susceptibility Patterns
GBS demonstrates excellent susceptibility to first-line agents 2, 3: