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Asymptomatic Bacteriuria Screening

Asymptomatic bacteriuria is defined as the presence of bacteria in the urine of a person without signs or symptoms of a urinary tract infection. Asymptomatic bacteriuria occurs when the urinary tract becomes colonized with significant amounts of pathogenic bacteria, primarily from the gastrointestinal tract. The most common pathogen isEscherichia coli, although other bacteria such asKlebsiella, Proteus mirabilis, and group B streptococcus may be involved.

The risk of developing asymptomatic bacteriuria varies by age, gender, and pregnancy status. Healthy, young, sexually active women have a prevalence of asymptomatic bacteriuria of 1% to 5%. For most of these women asymptomatic bacteriuria is transient. Prevalence is higher among patients with diabetes (10%-20%), spinal cord injury (30%), and urinary catheters (50%-70%) and those living in long-term care facilities (30%-50%). In many populations, asymptomatic bacteriuria may be protective. Treatment of these patients with antibiotics can paradoxically increase the risk of developing a urinary tract infection (UTI), selecting for antimicrobial resistance and increasing the risk of Clostridioides difficile infection.

An estimated 2 to 10% of pregnant women have asymptomatic bacteriuria. During pregnancy, physiologic changes that affect the urinary tract increase the risk of asymptomatic bacteriuria and symptomatic urinary tract infections, including pyelonephritis. Pyelonephritis is associated with perinatal complications including septicemia, respiratory distress, low birth weight, and spontaneous preterm birth

In 2019, USPSTF updated its 2008 recommendation on screening for asymptomatic bacteriuria. USPSTF concluded with moderate certainty that screening for and treatment of asymptomatic bacteriuria in nonpregnant adults hasno net benefit (D recommendation). USPSTF also concluded with moderate certainty that screening for and treatment of asymptomatic bacteriuria in pregnant persons has moderate net benefit in reducing perinatal complications (B recommendation). The morbidity of untreated asymptomatic bacteriuria in pregnant women is largely attributable to acute pyelonephritis occurring in later pregnancy, which may be complicated by severe sepsis or septic shock for some women and which may precipitate preterm labor and delivery.

Screening for asymptomatic bacteriuria during pregnancy is done with a urine culture at 12 to 16 weeks of gestation or at the first prenatal visit. Urine culture is currently recommended for screening in pregnancy and is the established method for diagnosis. A culture obtained using a midstream, clean-catch urine sample with greater than 100 000 colony-forming units (CFU) per milliliter of a single uropathogen is considered a positive test result. Greater than 10 000 CFU/mL of group B streptococcus is an indicator of vaginal colonization and is commonly used as the threshold for treatment of infection in pregnancy


US Preventive Services Task Force, Screening for Asymptomatic Bacteriuria in Adults: US Preventive Services Task Force Recommendation Statement, JAMA. 2019;322(12):1188-1194. doi:10.1001/jama.2019.13069

Ferroni M, Taylor AK. Asymptomatic bacteriuria in noncatheterized adults. Urol Clin North Am. 2015;42(4):537-545. doi:10.1016/j.ucl.2015.07.003

Nicolle LE et al; Infectious Diseases Society of America; American Society of Nephrology; American Geriatric Society. Infectious Diseases Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clin Infect Dis. 2005;40(5):643-654. doi:10.1086/427507

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