What Is Asymptomatic Bacteriuria?

Medically Reviewed by Dany Paul Baby, MD on June 26, 2022
4 min read

One of the most common infections treated by antibiotics is a urinary tract infection (UTI). Treatment guidelines are issued for uncomplicated and complicated cases. 

When there are bacteria in the urine but the patient doesn’t know, that is called asymptomatic bacteriuria. There are guidelines for treating it in differing populations. 

Asymptomatic bacteriuria is common in many people, including healthy women and those with underlying urologic issues.

Usually, your urine is sterile, but if you have the symptoms of a kidney or bladder infection, that means bacteria is current and multiplying in your urine. Asymptomatic bacteriuria is diagnosed when a urine culture has bacteria in it but you have no signs or symptoms of a UTI. Traditional UTI symptoms are painful urination, frequent urination, and fever. Asymptomatic bacteriuria is commonly associated with urine containing greater than 10 white blood cells under a microscope.  

Asymptomatic bacteriuria is found often in healthy women and both men and women with other medical abnormalities in the urinary tract that makes urination difficult.

Asymptomatic bacteriuria happens in a tiny number of healthy people. Women are affected more often than men, and the reason for the lack of symptoms is not well-known. You are more likely to suffer from asymptomatic bacteriuria if you:

  • Are a female
  • Are pregnant
  • Are sexually active
  • Have a urinary catheter
  • Have diabetes 
  • Are an older adult
  • Had recent surgery performed on your urinary tract

The occurrence of asymptomatic bacteriuria is fairly common depending on sex, age, sexual activity, and urinary tract abnormalities. In women that are healthy, bacteriuria prevalence increased from 1% in females 5 to 14 years in age to 20 % in women at least 80 years old.  

Escherichia coli is the most common specimen found in patients with asymptomatic bacteriuria. However, infectious agents are various and can come from Enterobacteriaceae, Enterococcus species Pseudomonas aeruginosa, and group B streptococcus. 

The organism present in the urine will depend on several variables. Many people will have E. coli. Nursing home residents, though, may have a drug-resistant polymicrobial flora like P. aeruginosa. Men usually have Gram-negative bacilli and enterococcus species. 

Asymptomatic bacteriuria is most common in women and those with abnormalities of the urinary system that make it hard for them to urinate. Asymptomatic bacteriuria was described first in early studies validating the use of urine cultures for urinary tract infections. A high number of positive cases were observed in women, and there were no symptoms. There were no other signs of urinary troubles attributed to infection.

One of the common dilemmas in clinical medicine is whether to treat patients without symptoms that have bacteria in their urine. There are some instances when antibiotic treatment of asymptomatic bacteriuria has shown to improve patient outcomes. Due to increasing antimicrobial resistance, though, it is important not to treat patients with asymptomatic bacteriuria unless evidence shows a potential benefit. 

Moms who are pregnant, for instance, should be screened and treated in the first trimester if positive. However, treating asymptomatic bacteriuria in those with catheters, diabetes, older people, or those with a spinal cord injury has not been proven to improve any outcomes.

Most of those with asymptomatic bacteriuria or asymptomatic pyuria will not be treated. Research has shown that treatment of asymptomatic bacteriuria does not prevent future urinary tract infections. It is, however, associated with future problems with antibiotic use and the development of future UTIs that are antibiotic-resistant. 

There are exceptions to these generalizations, though.

Nonpregnant, premenopausal women: These women with asymptomatic bacteriuria have no adverse effects usually. Most will clear up their bacteriuria without treatment. However, these women more than likely will experience recurrent UTIs with symptoms more often than women who have not had asymptomatic bacteriuria.

Pregnant women with asymptomatic bacteriuria: Infected pregnant women will likely deliver a low-birth-weight or premature baby, and have up to a 30-fold increase of contracting pyelonephritis during gestation when compared to those without asymptomatic bacteriuria. Research has reported that treatment of asymptomatic bacteriuria in those that are pregnant decreases pyelonephritis risk from up to 35% to about 4%. Antimicrobial treatment of bacteriuria improves fetal outcomes and decreases instances of tiny and preterm babies.

Women with diabetes: In studies, women with diabetes initially show no difference in asymptomatic bacteriuria from those without bacteria in the urine in terms of increased mortality, UTI risk, or diabetic complications after 18 months. One study compared antibiotic treatment with a lack of treatment in women with asymptomatic bacteriuria and diabetes. It showed that antibiotic treatment did not decrease the occurrence of a UTI with symptoms, nor did it decrease the UTI hospitalization rate after a 3-year follow-up.

Long-term care: Studies of asymptomatic bacteriuria in pre- and post-menopausal women show similar outcomes despite age. Ambulatory women in long-term care facilities who were given antibiotic treatment for asymptomatic bacteriuria showed a decrease in the occurrence of symptomatic bacteriuria at 6 months.

The Infectious Diseases Society of America recommends the following when it comes to screening for asymptomatic bacteriuria:

  • Infants and children should not be screened and treated for asymptomatic bacteriuria.
  • Healthy premenopausal and nonpregnant women, or those who are post-menopausal, should not ordinarily be screened.
  • Pregnant women should be screened and treated for asymptomatic bacteriuria.
  • Older persons who live in community dwellings that are functionally impaired should not be screened for asymptomatic bacteriuria.
  • Screening is not recommended for kidney transplant patients who had transplant surgery less than a month ago.  

Show Sources


Agency for Healthcare Research and Quality: "Asymptomatic Bacteriuria."

American Family Physicians: "Asymptomatic Bacteriuria in Adults."

Infectious Disease Society of America: "Clinical Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 Update by the Infectious Diseases Society of America."

Mount Sinai: "Asymptomatic bacteriuria."

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