Catheter-Associated UTIs: How Infection Occurs

Urinary tract infections are one of the most common healthcare-associated infections (HAIs) in the US, accounting for 30% of all reported cases.  Approximately 75% of these UTIs are associated with the use of urinary catheters1, which are called catheter-associated UTIs. Patients with long term catheterization have been shown to have a higher risk of developing a catheter-associated biofilm infection.

In the US, more than five million hospital and nursing home patients require urinary catheterization every year2. This process is illustrated in the images above. During urinary catheterization, a thin flexible plastic tube is lubricated and inserted into a patient’s urethra. Once the catheter enters the bladder, a small balloon is inflated to hold the tube in place. A urine drainage bag with an emptying spout is connected to the external end of the catheter. This end collects the urine.

Patients inserted with urinary catheters are at higher risk of developing catheter-associated UTIs. These infections are primarily caused by E. coli, a species of bacteria  found in the colon that has managed to work its way along the catheter into the bladder. Once in the bladder, the bacteria are able to settle and reproduce easily, leading to infection.  Symptoms of catheter-associated UTIs may be minimal but include cloudy urine and the urge to urinate frequently. One of the greatest health risks for patients is if the infection moves from the bladder up into the kidneys which in turn may cause a life threatening bloodstream infection. The incidence of catheter-associated UTIs is greatest amongst patients who are incapacitated in some manner and require catheterization for long periods of time.

In patients who do develop kidney infections (pyelonephritis), they may require treatment with multiple antibiotics to try and eliminate the offending organisms. In too many cases, the organisms are resistant to antibiotics. It has therefore become a primary goal of hospitals to try and eliminate the causes of severe kidney infections such as prolonged bladder catheterization which will result in inevitable biofilm growth on the catheter.

Recently, attention has appropriately focused on biofilm development on and within urinary catheters. As we’ve mentioned in a previous blog post, biofilm infections are estimated to represent up to 80% of all human infections, including catheter-associated UTIs. Biofilms on urinary catheters are notoriously difficult to eradicate and can be responsible for infections that are resistant to both host defenses and antimicrobial therapy.

Techniques for preventing the formation of biofilms on catheters are currently being developed, but few have been proven clinically effective4. The latest research continues to further our understanding of how biofilms form on urinary catheters, and will encourage the development of better ways to prevent catheter-associated UTIs. One promising new approach to this problem is the use of antimicrobial photodynamic disinfection which has been demonstrated to be very effective at killing and preventing biofilms. In addition, it has the added benefit of not promoting antibiotic resistance. With minimal modifications, catheters could potentially be designed to make use of this technology to prevent internal and external catheter biofilm formation.

  1. CDC http://www.cdc.gov/HAI/ca_uti/uti.html
  2. Centers for Disease Control and Prevention: http://www.cdc.gov/ncidod/eid/vol7no2/maki.htm
  3. Hooton TM, Bradley SF, Cardenas DD, et al. Diagnosis, prevention, and treatment of catheter-associated urinary tract infection in adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis. 2010;50:625-663.
  4. Hatt et al. Role of Bacterial Biofilms In Urinary Tract Infections. Current Topics In Microbiology & Immunology 2008, Vol 322:163-92.

Image source: Health Central http://www.healthcentral.com/incontinence/treatment-000050_16-145.html

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One Response to “Catheter-Associated UTIs: How Infection Occurs”

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