For an asymptomatic patient with a urinary sample showing Escherichia coli (E. coli), how long can we wait to start antibiotics?

Do Not Start Antibiotics for Asymptomatic Bacteriuria with E. coli

For an asymptomatic patient with E. coli in the urine, antibiotics should not be started at all—there is no appropriate waiting period because treatment is not indicated. 1

Key Principle: Asymptomatic Bacteriuria Does Not Require Treatment

The presence of bacteria in urine without symptoms is called asymptomatic bacteriuria (ASB), and this is a fundamentally different condition from a urinary tract infection. 1, 2

• Pyuria (white blood cells in urine) accompanying asymptomatic bacteriuria is NOT an indication for treatment. 1 Many clinicians mistakenly treat based on pyuria alone, but this leads to unnecessary antibiotic exposure.

• The Infectious Diseases Society of America provides a strong recommendation with moderate-quality evidence against screening for or treating ASB in most patient populations. 1

Specific Populations Where Treatment is NOT Indicated

The following groups should never receive antibiotics for asymptomatic bacteriuria 1:

• Premenopausal, nonpregnant women
• Diabetic women
• Older persons living in the community
• Elderly institutionalized patients
• Patients with spinal cord injury
• Patients with short-term indwelling catheters (<30 days) while catheter remains in place
• Patients with long-term indwelling catheters
• Patients undergoing elective non-urologic surgery 1, 3

Only Two Exceptions Where Treatment IS Indicated

1. Pregnant Women

• Screen all pregnant women with urine culture at 12-16 weeks gestation and treat if positive with 3-7 days of antibiotics. 1, 4
• Untreated ASB leads to pyelonephritis in 20-35% of pregnant women versus only 1-4% when treated. 4

2. Before Urologic Procedures with Mucosal Bleeding

• Screen and treat ASB before transurethral resection of the prostate or other urologic procedures that breach the mucosa. 1
• Antimicrobial therapy should be initiated shortly before the procedure, not days in advance. 1
• Without treatment, bacteremia occurs in up to 60% and sepsis in 6-10% of bacteriuric patients undergoing transurethral prostatic resection. 1

Harms of Treating Asymptomatic Bacteriuria

Treating ASB when not indicated causes significant harm 1, 3, 5:

• Promotes antimicrobial resistance through selective pressure for resistant organisms
• Increases risk of Clostridioides difficile infection (0.9% vs 0% in one study) 5
• Prolongs hospitalization (mean 5.1 vs 4.2 days) 5
• Does not prevent symptomatic UTIs or improve clinical outcomes 1, 3

Common Clinical Pitfall to Avoid

Do not treat bacteriuria in elderly patients with delirium, confusion, or falls unless they have local genitourinary symptoms (dysuria, frequency, urgency, suprapubic pain) or systemic signs (fever, hemodynamic instability). 1

• The IDSA provides a strong recommendation to assess for other causes of delirium and observe rather than treat the bacteriuria. 1
• This recommendation prioritizes avoiding C. difficile infection, antimicrobial resistance, and adverse drug effects in vulnerable populations. 1

What Constitutes Symptoms Requiring Treatment

Antibiotics are only indicated when patients develop true UTI symptoms 1, 3:

• Dysuria (painful urination)
• Urinary frequency
• Urinary urgency
• Suprapubic pain
• Fever without another identified source
• Hemodynamic instability with suspected urinary source

Special Consideration: Catheter Removal

For asymptomatic women with catheter-acquired bacteriuria that persists 48 hours after catheter removal, antimicrobial treatment may be considered (though this is the only gray area in the guidelines). 1