Should an 80-year-old patient with asymptomatic bacteriuria (ASB) due to 100,000 colony-forming units (CFU) of Escherichia coli (E. coli) per milliliter of urine from a Foley catheter receive antibiotics?

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Last updated: May 14, 2025 • View editorial policy

From the Guidelines

No, an 80-year-old patient with 100,000 E. coli in her urine through a Foley catheter but no symptoms should not receive antibiotics. This condition represents asymptomatic bacteriuria, which is extremely common in catheterized elderly patients and does not require treatment, as stated in the 2019 clinical practice guideline for the management of asymptomatic bacteriuria by the Infectious Diseases Society of America 1. Treating asymptomatic bacteriuria in catheterized patients does not reduce complications or improve outcomes, but instead increases the risk of developing antibiotic resistance and potential side effects like Clostridioides difficile infection. Key points to consider in this scenario include:

  • The presence of bacteria in the urine is expected with indwelling catheters and becomes nearly universal after 30 days of catheterization.
  • There is high-quality evidence that antimicrobials cause harm, including adverse effects and increasing costs, as well as increasing the risk of antimicrobial-resistant infections in the individual and the community 1.
  • Instead of antibiotics, focus should be on:
    • Evaluating the continued need for the catheter
    • Proper catheter care
    • Monitoring for the development of actual urinary tract infection symptoms such as fever, altered mental status, flank pain, or catheter obstruction Only if symptoms develop would antibiotic treatment be warranted, as supported by the guideline 1.

From the FDA Drug Label

To reduce the development of drug-resistant bacteria and maintain the effectiveness of sulfamethoxazole and trimethoprim tablets and other antibacterial drugs, sulfamethoxazole and trimethoprim tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria The patient should not receive antibiotics because there are no symptoms of a urinary tract infection, and the presence of 100,000 E. coli in the urine through a Foley catheter alone is not sufficient to warrant antibiotic treatment, as this may be a case of asymptomatic bacteriuria.

  • The FDA drug label does not provide guidance on the treatment of asymptomatic bacteriuria in patients with Foley catheters.
  • The decision to treat should be based on clinical judgment and consideration of the patient's individual risk factors and medical history 2

From the Research

Asymptomatic Bacteriuria in an 80-Year-Old Patient

  • The patient has 100,000 E. coli in her urine through a Foley catheter but no symptoms.
  • According to the studies 3, 4, 5, 6, 7, asymptomatic bacteriuria is a common condition in elderly patients, especially those with indwelling catheters.
  • The guidelines recommend against screening and treatment in patients with asymptomatic bacteriuria, including those with indwelling catheters, unless they are undergoing urological procedures or are pregnant 4, 5, 6.

Treatment Recommendations

  • The Infectious Diseases Society of America recommends treating asymptomatic bacteriuria only in pregnant women and individuals undergoing endourological procedures associated with mucosal trauma 4, 5, 6.
  • For patients with asymptomatic bacteriuria and no symptoms, treatment is not recommended, as it has not been shown to improve clinical outcomes and may contribute to antimicrobial resistance 3, 4, 5, 6, 7.
  • In this case, since the patient is 80 years old and has no symptoms, treatment with antibiotics is not recommended, unless there are other underlying conditions that may require treatment, such as a planned urological procedure.

Risks of Unnecessary Treatment

  • Unnecessary treatment of asymptomatic bacteriuria can lead to adverse effects, including Clostridioides difficile infection, and contribute to antibiotic resistance 4, 5, 6, 7.
  • The studies suggest that asymptomatic bacteriuria does not typically lead to urinary tract infections, and treatment has not been shown to improve patient outcomes 3, 4, 5, 6, 7.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.