Asymptomatic bacteriuria: is it associated with adverse outcomes and should it be treated?
While there is no doubt that symptomatic urinary tract infections (UTI) should be treated, one is faced with uncertainty if presented with a positive urine culture report in the absence of signs and symptoms of UTI.
Screening of asymptomatic subjects for bacteriuria is appropriate if bacteriuria has adverse outcomes that can be prevented by antimicrobial therapy. Important short term outcomes include symptomatic urinary infection, bacteremia with sepsis, and longer term outcomes, such as progression to chronic kidney disease or hypertension, development of urinary tract cancer, or decreased duration of survival.
Treatment of asymptomatic bacteriuria may itself be associated with undesirable outcomes, including subsequent antimicrobial resistance, adverse drug effects, and cost. If treatment of bacteriuria is not beneficial, screening of asymptomatic populations to identify bacteriuria is not indicated. The diagnosis of asymptomatic bacteriuria should be based on results of culture of a urine specimen collected in a manner that minimizes contamination, i.e. midstream sample
Pyuria (presence of pus cells on urine microscopy or dipstick) is evidence of inflammation in the genitourinary tract and is common in subjects with asymptomatic bacteriuria. Pyuria is present with asymptomatic bacteriuria in 32% of young women, 30% 70% of pregnant women, 70% of diabetic women, 90% of elderly institutionalized patients, 90% of hemodialysis patients, 30% 75% of bacteriuric patients with short-term catheters in place, and 50% 100% of individuals with long-term indwelling catheters in place. Pyuria also accompanies other inflammatory conditions of the genitourinary tract in patients with negative urine culture results. These may be either infectious, such as renal tuberculosis and sexually transmitted diseases, or noninfectious, such as interstitial nephritis. Thus, by itself, the presence of pyuria is not sufficient to diagnose bacteriuria, and the presence or absence of pyuria does not differentiate symptomatic from asymptomatic urinary infection.
Asymptomatic bacteriuria is common, but the prevalence in populations varies widely with age, sex, and the presence of genitourinary abnormalities. For healthy women, the prevalence of bacteriuria increases with advancing age, from 1% among schoolgirls to >20% among healthy women 80 years of age living in the community. The prevalence of bacteriuria among young women is strongly associated with sexual activity. Pregnant and nonpregnant women have a similar prevalence of bacteriuria (2% 7%). Bacteriuria is more common in diabetic women, with a prevalence of 8% 14%, and is usually correlated with duration of diabetes and presence of long-term complications of diabetes, rather than with metabolic parameters of diabetic control. Asymptomatic bacteriuria is rare in healthy young men. The prevalence in men increases substantially after the age of 60 years, presumably because of obstructive uropathy and voiding dysfunction associated with prostatic hypertrophy. From 6% to 15% of men >75 years of age who reside in the community are bacteriuric. Diabetic men do not appear to have an increased prevalence of bacteriuria, compared with nondiabetic men.
For asymptomatic women, bacteriuria is defined as 2 consecutive voided urine specimens with isolation of the same bacterial strain in quantitative counts 105 cfu/mL.
For asymptomatic men, a single, clean-catch voided urine specimen with 1 bacterial species isolated in a quantitative count 105 cfu/mL identifies bacteriuria.
A single catheterized urine specimen with 1 bacterial species isolated in a quantitative count 102 cfu/mL identifies bacteriuria in women or men.
Infectious Diseases Society of America (IDSA) recommends:
1. Pyuria accompanying asymptomatic bacteriuria is not an indication for antimicrobial treatment.
2. Pregnant women should be screened for bacteriuria by urine culture at least once in early pregnancy, and they should be treated if the results are positive (there is a risk of adverse outcome). The duration of antimicrobial therapy should be 3 7 days and periodic screening for recurrent bacteriuria should be undertaken following therapy.
3. Screening for and treatment of asymptomatic bacteriuria before transurethral resection of the prostate and other urologic procedures for which mucosal bleeding is anticipated, is recommended
4. Screening for or treatment of asymptomatic bacteriuria is not recommended for the following persons.
· Premenopausal, nonpregnant women
· Diabetic women
· Older persons living in the community
· Persons with spinal cord injury
· Catheterized patients while the catheter remains in situ