Is antibiotic treatment indicated in a patient with a positive urine culture but no symptoms?

WHAT IS THE EVIDENCE FOR NO TREATMENT?

Asymptomatic bacteriuria should not be screened for or treated in: 

• Premenopausal women who are not pregnant (grade A-I recommendation)
• Diabetic women (A-I)
• Older persons residing in the community (A-II)
• Elderly residents of long-term care facilities (A-I)
• Patients with spinal cord injury (A-I)
• Patients with an indwelling urethral catheter (A-I).

Randomized controlled trials comparing antibiotic therapy with no therapy in these groups showed no benefit of antibiotic treatment in reducing the frequency of symptomatic urinary tract infection^11–16 and no decrease in rates of fever or reinfection in patients with a long-term catheter.¹⁷ Moreover, in a number of trials,^12,14,17 antibiotic therapy for asymptomatic bacteriuria was associated with an increase in adverse antimicrobial effects and reinfection with resistant organisms.

In transplant recipients. Because of lack of evidence, the 2005 IDSA guidelines could not make a recommendation for or against screening for or treatment of asymptomatic bacteriuria in renal transplant or other solid-organ transplant recipients (C-III). A more recent review¹⁸ noted a lack of consensus as to whether asymptomatic bacteriuria should be treated in renal transplant recipients. Based on available data, the authors recommended limiting routine screening for it to the first 1 to 3 months after renal transplantation and limiting treatment to 5 to 7 days, using the narrowest-spectrum antibiotic available.¹⁸

In prosthetic joint recipients. The 2005 IDSA guidelines recommended further research to determine if screening and treatment before surgical procedures with prosthetic implantation have clinical benefit.

A positive culture should not be treated in a patient whose symptoms are attributable to another cause

Since then, two studies^19,20 have suggested no benefit of screening or treatment before prosthetic joint implantation. Rates of prosthetic joint infection were not different in patients with asymptomatic bacteriuria before hip arthroplasty randomized to receive no antibiotic therapy vs those receiving antibiotic therapy specific for organisms cultured from the urine.¹⁹ Asymptomatic bacteriuria was found to be an independent risk factor for prosthetic joint infection.²⁰ However, rates of joint infection were not different in those treated with antibiotics than in those not treated, and in no case were the microorganisms isolated in the prosthetic joint infection the same as in their preoperative urine culture.²⁰

The authors concluded that asymptomatic bacteriuria may be a surrogate marker for increased risk of infection, but that preoperative antibiotic treatment was not beneficial.²⁰

WHAT DOES 'ASYMPTOMATIC' MEAN?

According to the definition, asymptomatic refers to patients who do not have symptoms or signs attributable to a urinary tract infection. Thus, in patients who have symptoms or signs clearly attributable to another condition, screening with urine culture testing and treatment are not indicated. In nursing home residents, nonspecific symptoms such as a change in mental status, fever, and leukocytosis should not automatically be attributed to a positive urine culture without a careful evaluation for another cause, given the high prevalence of asymptomatic bacteriuria in this population.²¹ Screening with urine culture testing in this population is also not recommended for isolated foul-smelling or cloudy urine, after every urethral catheter change, upon admission, or after treatment to document cure.²² 

Finally, pyuria (defined as the presence of at least 5 to 10 white blood cells per high-power field) is not by itself a reason to perform a urine culture or to treat a positive urine culture, since pyuria is common in asymptomatic bacteriuria, as well as in other conditions associated with inflammation in the genitourinary system.¹

TAKE-HOME POINTS

• Screening for and treating asymptomatic bacteriuria is recommended for pregnant women and for patients about to undergo an invasive urologic procedure associated with significant mucosal injury
• Screening and treatment are not recommended for premenopausal nonpregnant women, diabetic women, older persons residing in the community, elderly residents of long-term care facilities, patients with spinal cord injury, or patients with an indwelling urethral catheter.
• A urine culture should not be ordered, but if it is ordered, a positive culture should not be treated in a patient whose symptoms are attributable to another cause.
• Pyuria is not helpful in distinguishing symptomatic from asymptomatic bacteriuria.