Do Not Treat Lactobacillus in Asymptomatic Pregnant Women
Lactobacillus species isolated from urine cultures in asymptomatic pregnant women should not be treated with antibiotics, as these are commensal organisms representing contamination or normal flora rather than true pathogenic bacteriuria. 1
Why Lactobacillus is Different from True Bacteriuria
Lactobacillus species are normal colonizers of the vaginal and periurethral area that frequently contaminate urine specimens, particularly in pregnant women. 1 The established guidelines for screening and treating asymptomatic bacteriuria in pregnancy specifically target uropathogens—organisms that cause ascending infection and pyelonephritis. 1 Lactobacillus does not fit the microbiological criteria for pathogenic bacteriuria that screening and treatment recommendations were designed to address. 1
What Should Be Treated in Pregnancy
The rationale for treating asymptomatic bacteriuria in pregnancy is compelling for true uropathogens:
- Untreated pathogenic bacteriuria leads to pyelonephritis in 20-35% of pregnant women, compared to only 1-4% when treated. 2
- Treatment reduces preterm birth risk from approximately 53 per 1000 to 14 per 1000. 2
- Treatment reduces very low birth weight from approximately 137 per 1000 to 88 per 1000. 2
However, these benefits apply only to true uropathogens such as E. coli, Klebsiella, Proteus, Enterococcus, and Group B Streptococcus. 1
Clinical Approach to Lactobacillus Bacteriuria
If a urine culture grows Lactobacillus species, consider this a contaminated specimen or normal flora rather than true bacteriuria—no antibiotic treatment is indicated. 1
The American College of Obstetricians and Gynecologists recommends treating asymptomatic bacteriuria with antibiotics only when a true uropathogen is identified. 1 Lactobacillus is explicitly excluded from this recommendation.
Common Pitfalls to Avoid
- Do not reflexively treat all positive urine cultures in pregnancy. The organism matters—Lactobacillus is not a pathogen in this context. 1
- Distinguish Lactobacillus from Group B Streptococcus. Group B Streptococcus bacteriuria at any concentration requires both immediate treatment and intrapartum prophylaxis during labor. 1
- Avoid unnecessary antibiotic exposure. Treating non-pathogenic organisms like Lactobacillus contributes to antimicrobial resistance without providing benefit to mother or fetus. 1
When to Actually Treat in Pregnancy
First-line therapy for confirmed asymptomatic bacteriuria with true uropathogens is nitrofurantoin 100 mg twice daily for 4-7 days, or cephalexin 500 mg four times daily for 4-7 days as an alternative. 1 This applies only to pathogenic bacteria, not Lactobacillus. 1