Treatment of Lactobacillus Urinary Tract Infection
Lactobacillus isolated from urine typically represents contamination or colonization rather than true infection and should not be treated with antibiotics in most cases. 1
Understanding Lactobacillus in Urine
Lactobacillus species are normal commensal organisms of the urogenital tract, not typical uropathogens. When isolated from urine cultures, they usually indicate:
- Contamination from periurethral/vaginal flora during specimen collection 2
- Colonization without active infection 1
- Protective organisms that actually prevent UTIs rather than cause them 3, 4
Lower urogenital lactobacillus colonization is actually associated with increased risk of UTI in infants and women, suggesting these organisms play a protective role 2.
When to Consider True Lactobacillus Infection
True pathogenic Lactobacillus UTI is exceptionally rare but may occur in specific circumstances:
- Severe urinary obstruction with stasis (e.g., ureteral stone) 5
- Diabetes mellitus 5
- Immunosuppression 6
- Presence of foreign body or catheter 6
- Signs of systemic infection (fever, sepsis, bacteremia) 5
A single case report from 1984 documented Lactobacillus gasseri causing septic UTI in a diabetic patient with severe urinary obstruction and ureteral stone, requiring catheterization and treatment with cefotaxime plus amoxicillin 5.
Diagnostic Approach
Before treating, confirm true infection versus colonization:
- Obtain urine culture with ≥50,000 CFU/mL of Lactobacillus as a single organism 1
- Document pyuria (white blood cells) and bacteriuria on urinalysis 1
- Assess for systemic symptoms (fever, rigors, altered mental status, flank pain) 6
- Identify underlying complicating factors (obstruction, foreign body, diabetes, immunosuppression) 6
- Rule out specimen contamination by obtaining a clean-catch or catheterized specimen 6
Treatment Algorithm
For Asymptomatic Bacteriuria with Lactobacillus:
Do not treat. Treating asymptomatic bacteriuria increases antimicrobial resistance risk without clinical benefit 1.
For True Symptomatic Lactobacillus UTI (Rare):
First-line therapy:
- Amoxicillin-clavulanate 875/125 mg every 12 hours for 7-14 days 1
- Address underlying urological abnormality (remove obstruction, drain abscess, replace catheter if present >2 weeks) 6
Duration considerations:
- 7 days for uncomplicated cases with prompt symptom resolution 6
- 10-14 days for complicated UTI or delayed response 6
- 14 days for men when prostatitis cannot be excluded 6
For catheter-associated cases:
- Replace catheter if in place ≥2 weeks before initiating antibiotics 6
- Obtain urine culture from freshly placed catheter 6
Critical Pitfalls to Avoid
- Do not reflexively treat Lactobacillus isolated from urine cultures - this usually represents normal flora, not infection 1, 2
- Do not treat asymptomatic bacteriuria - this increases resistance without benefit 1
- Do not ignore underlying structural abnormalities - these must be corrected for treatment success 6
- Do not assume contamination if patient has systemic symptoms with obstruction - rare true infections can occur 5
Role of Lactobacillus as Prophylaxis
Paradoxically, Lactobacillus supplementation (particularly L. rhamnosus GR-1 and L. reuteri RC-14) may prevent recurrent UTIs rather than cause them:
- Vaginal lactobacillus suppositories reduced UTI recurrence to 21% versus 47% with placebo 3
- Lactobacillus prophylaxis showed comparable efficacy to trimethoprim-sulfamethoxazole for preventing recurrent UTIs in children with VUR 6
- For recurrent UTIs, consider vaginal estrogen with lactobacillus probiotics in postmenopausal women 1