A urinary catheter is a medical tool whose use is associated with a risk of infection. These catheter-associated urinary tract infections (CAUTIs) are a common concern in healthcare settings, occurring when microbes enter the urinary tract during catheter use. Understanding the bacteria involved and prevention methods is important for patient safety.
Understanding Urinary Catheters
A urinary catheter is a flexible tube inserted into the bladder to drain urine. This device is used for medical reasons, such as when a person cannot empty their bladder on their own, a condition known as urinary retention. It is also used during and after certain surgeries or to accurately measure urine output. For individuals with neurological conditions that affect bladder control, catheters provide a way to manage urination.
There are several types of urinary catheters. Indwelling catheters, often called Foley catheters, are designed to remain in the bladder for an extended period and are held in place by a small, inflated balloon that drains into a collection bag. Intermittent catheters are used for short-term bladder emptying and are removed immediately after use. A suprapubic catheter is inserted directly into the bladder through a small incision in the abdomen.
How Catheters Can Lead to Infections
A urinary catheter disrupts the body’s natural defenses, creating a direct pathway for bacteria to enter the urinary tract. Microbes can travel along the outside of the catheter or through the inside of the tube if the drainage system becomes contaminated. The daily risk of acquiring bacteria in the urine is estimated to be 3-10% for each day an indwelling catheter is in place.
A primary mechanism behind these infections is the formation of biofilm. Bacteria attach to the catheter surface and begin to multiply, forming a community embedded in a self-produced slimy matrix. This biofilm acts as a protective shield for the bacteria, making them more resistant to the body’s immune response and antibiotics.
The most significant risk factor is the duration of catheterization; the longer a catheter remains in place, the higher the chance of infection. Other contributing factors include being female, older age, and having underlying health conditions like diabetes. Any break in sterile technique during catheter insertion or maintenance can also introduce bacteria.
Common Bacteria in Catheter-Related Infections
A variety of bacteria cause CAUTIs, many originating from the patient’s own gut flora. The most frequently identified bacterium is Escherichia coli (E. coli), which is responsible for a significant percentage of CAUTIs. E. coli has features that help it attach to the catheter surface and move within the urinary system, facilitating colonization.
Other common Gram-negative bacteria include Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis. Klebsiella pneumoniae is often the second most common cause and can form biofilms. Pseudomonas aeruginosa is known for its robust biofilms and resistance to many antibiotics. Proteus mirabilis is adept at attaching to catheter materials and is a frequent cause of infection in patients with long-term catheters.
Gram-positive bacteria, such as Enterococcus species and Staphylococcus species, are also implicated in CAUTIs. Fungi, particularly Candida species, can also cause these infections, especially in patients with long-term catheters or those treated with broad-spectrum antibiotics. Infections can sometimes be polymicrobial, meaning they are caused by more than one type of microbe.
Recognizing and Treating Catheter Infections
Identifying a catheter-associated infection involves looking for specific signs and symptoms. Localized symptoms may include pain above the pubic bone or cloudy, foul-smelling urine. Systemic signs of infection, such as fever and chills, are also common indicators. In older adults, new or worsening confusion or delirium might be the primary sign of a CAUTI.
Diagnosis is confirmed through laboratory tests. A urinalysis may be performed to look for white blood cells, which indicate inflammation. A definitive diagnosis relies on a urine culture to identify the specific bacteria and determine which antibiotics will be effective. For an accurate culture, the urine sample should be collected after replacing the old catheter with a new one.
Treatment for a symptomatic CAUTI involves a course of antibiotics, guided by the results of the urine culture. A main component of treatment is the removal or replacement of the urinary catheter whenever possible. For patients who are high-risk or show signs of a more serious infection, treatment may begin with a broad-spectrum antibiotic while awaiting culture results.
Preventing Catheter-Associated Infections
The most effective way to prevent catheter-associated urinary tract infections is to avoid using indwelling catheters whenever possible. When a catheter is medically necessary, it should be removed as soon as it is no longer needed. Using reminders or protocols that prompt healthcare staff to review the need for a catheter can lead to earlier removal and lower infection rates.
Proper insertion and maintenance are also important for prevention.
- Catheters must be inserted by trained personnel using a sterile technique.
- A closed drainage system must be maintained to prevent bacteria from entering.
- The collection bag should always be kept below the level of the bladder to prevent the backflow of urine, and it should not touch the floor.
- Hand hygiene must be performed before and after handling the catheter or drainage system.
- Routine cleaning of the area where the catheter enters the body is also recommended.
Alternatives like intermittent catheterization or external “condom” catheters for men may be suitable in certain situations and carry a lower risk of infection.