What is the significance of Lactobacillus (a type of bacteria) in a urine culture?

From the Guidelines

Lactobacillus in a urine culture is not considered a clinically relevant urine isolate for otherwise healthy individuals, and its presence does not typically require treatment. According to the American Academy of Pediatrics guideline for the diagnosis and management of urinary tract infections in febrile infants and children 2 to 24 months 1, organisms such as Lactobacillus spp are not considered significant urinary pathogens. The guideline suggests that an appropriate threshold to consider bacteriuria “significant” in infants and children is the presence of at least 50 000 CFUs per mL of a single urinary pathogen, but this does not apply to Lactobacillus.

Some key points to consider when evaluating a urine culture with Lactobacillus include:

• The method of collection, as the distal urethra and periurethral area are commonly colonized by the same bacteria that may cause UTI, and a low colony count may be present in a specimen obtained through voiding or catheterization when bacteria are not present in bladder urine 1
• The time the urine resides in the bladder, as this is an important determinant of the magnitude of the colony count 1
• The presence of symptoms, as patients with urinary symptoms despite finding only Lactobacillus may require further evaluation to look for other causes

In general, no specific treatment is needed for Lactobacillus alone in urine, as these are normal flora that often contaminate urine samples during collection. However, in rare cases where Lactobacillus is causing true infection, typically in immunocompromised patients, treatment with ampicillin or amoxicillin at standard doses for 3-5 days may be effective, but this should be guided by clinical judgment and susceptibility testing.

From the Research

Lactobacillus in Urine Culture

• Lactobacilli are part of the normal bacterial flora of the vagina and are typically considered contaminants when cultured from urine specimens of female patients 2.
• However, there have been cases where Lactobacillus species, such as Lactobacillus delbrueckii, have been determined to be the causative microorganism of urinary tract infections (UTIs) 2.
• The presence of Lactobacillus in urine culture may require further evaluation to determine if it is a contaminant or a pathogen.
• UTIs are typically caused by other microorganisms, such as Escherichia coli, which is the most frequently isolated microorganism from urine cultures 3.
• The treatment of UTIs usually involves the use of antibiotics, such as nitrofurantoin, fosfomycin, or pivmecillinam, which are effective against common uropathogens 4, 5.

Antibiotic Susceptibility

• The susceptibility of Lactobacillus species to antibiotics is not well established, and further research is needed to determine the most effective treatment options 2.
• However, studies have shown that Lactobacillus species may be resistant to certain antibiotics, such as trimethoprim-sulfamethoxazole and ciprofloxacin 3, 6.
• The choice of antibiotic for the treatment of UTIs should be based on the results of urine culture and susceptibility testing, as well as local resistance patterns 4, 5.

Clinical Implications

• The presence of Lactobacillus in urine culture should be evaluated in the context of the patient's clinical presentation and medical history.
• Further research is needed to determine the clinical significance of Lactobacillus in urine culture and to establish guidelines for its treatment 2, 3.
• Clinicians should be aware of the potential for Lactobacillus species to cause UTIs and should consider this possibility when evaluating patients with urinary tract symptoms 2, 5.