Management of Urine Culture with >100,000 Units of Lactobacillus
Lactobacillus species in urine cultures with >100,000 CFU/mL do not require antimicrobial treatment as they are not considered clinically relevant urinary pathogens in otherwise healthy individuals. 1
Clinical Significance of Lactobacillus in Urine
- Lactobacillus species are explicitly identified in clinical guidelines as organisms that are not considered clinically relevant urine isolates for otherwise healthy individuals 1
- The American Academy of Pediatrics guidelines specifically state that "Organisms such as Lactobacillus spp, coagulase-negative staphylococci, and Corynebacterium spp are not considered clinically relevant urine isolates" 1
- Lactobacillus species are part of the normal human flora and are generally assumed to be nonpathogenic 2
Diagnostic Considerations
- True urinary tract infections (UTIs) are diagnosed based on both:
- Quantitative urine culture results AND
- Evidence of pyuria and/or bacteriuria 1
- The presence of Lactobacillus alone, even at high colony counts, does not constitute a UTI 1
- Treating asymptomatic bacteriuria may be harmful and should be avoided 1
When to Consider Treatment
Treatment might be warranted only in specific clinical scenarios:
- If the patient has symptoms of UTI (dysuria, urgency, frequency) AND evidence of pyuria 1, 3
- In immunocompromised patients or those with underlying urological abnormalities 2
- If Lactobacillus is isolated from a sterile site (not just urine) 2
Potential Harms of Unnecessary Treatment
- Promoting antimicrobial resistance 4
- Unnecessary antimicrobial-related adverse events 4
- Increased healthcare costs 4
- Disruption of normal urogenital flora, which may actually predispose to true UTIs 5
- Studies show that after antibiotic treatment, the indigenous lactobacillus population is often not restored, allowing uropathogenic bacteria to dominate 5
Common Pitfalls in Management
- Overinterpreting laboratory data such as colony counts without considering the organism identity 4
- Treating asymptomatic bacteriuria, which guidelines explicitly recommend against 1
- Failing to distinguish between true UTI pathogens and normal flora/colonizers 2
- Not recognizing that some Lactobacillus species are deliberately used as probiotics for their beneficial effects 2
Conclusion for Clinical Practice
When encountering a urine culture with >100,000 CFU/mL of Lactobacillus:
- Do not treat with antibiotics if the patient is asymptomatic 1
- Consider the organism identity (Lactobacillus) as non-pathogenic in most contexts 1, 2
- Look for evidence of pyuria if considering treatment 1
- Reserve antimicrobial therapy for cases with clear evidence of infection with recognized uropathogens 1