Infection Protection is a monthly column dedicated to education about infection control issues. This month’s column discusses catheter-associated urinary tract infections. Every fourth issue includes a Q&A forum to answer questions you have about the infection control information presented here. If you have a question, please submit it to jakridge@hpnonline.com or call (941)927-9345 ext. 202.

Cynthia T. Crosby
Vice President, Clinical Affairs
Medi-Flex, Inc.

According to NNIS data, UTIs are the most common nosocomial infection, accounting for 40% of all hospital-reported infections and affecting approximately 600,000 patients annually.1,2 Catheter insertion is the primary risk factor for nosocomial UTIs. Women and elderly patients are at increased risk for catheter-associated UTIs, but several other risk factors exist. Pre-existing chronic illness, malnutrition, diabetes, renal insufficiency, and insertion of the catheter outside the operating room or late in hospitalization are each associated with increased risk of UTIs.1,3 In addition to causing morbidity, UTIs also contribute directly to mortality in approximately 0.1% of patients annually in the United States.1 UTIs also add to the costs of care by prolonging hospitalization by 1 to 4 days and increasing the direct costs of treatment by an estimated $593 to $680 per infection.1,4

Prevention guidelines
Guidelines to prevent catheter-associated UTIs were published in 1981 and are promoted by the Centers for Disease Control (CDC).2 Although these guidelines are not recent, they provide a foundation of evidence-based infection control recommendations that are still relevant today. These recommendations are summarized in Table 1. In addition to these guidelines, more recent practice interventions and new devices have been shown to reduce catheter-associated UTIs. New research, particularly regarding the effect of biofilms on catheter-associated UTIs, also has affected treatment options.

Biofilms and UTIs
Biofilms consist of microorganisms that adhere together, along with their extracellular deposits and host proteins. They can develop either within the catheter lumen, on the external surface, or on both surfaces.3 Biofilms on or within urinary catheters are known to cause UTIs that are persistent and generally resistant to antimicrobial therapy.5,6 Therefore, the use of indwelling catheters should be avoided or used for limited durations to reduce exposure to biofilm infections.7 When catheters must be used and infection is suspected, the catheter should be changed to remove the presence of the biofilm and improve response to antimicrobial therapy.6 Research is focusing on methods to disrupt the formation of biofilms on catheter surfaces.

Practice interventions
Prevention of catheter-associated UTIs is more effective, particularly for indwelling catheters, than relying solely on antimicrobial agents.8 The most effective practice interventions for reducing catheter-associated UTIs include identifying patients who no longer need indwelling catheters, considering other catheterization options or alternatives to catheterization, and providing patient and caregiver education when long-term indwelling catheterization is needed.9

Reducing the time a patient is catheterized can be accomplished by systematic reminders to review the duration of catheterization for each patient. An interventional study in which physicians were reminded daily to remove unnecessary catheters significantly reduced the number of catheter days from 7 to 4.6 (P<0.001), which reduced the rate of catheter-associated UTIs from 11.5 to 8.3 per 1000 catheter-days (P= 0.009). This intervention also resulted in a 69% decrease in the monthly cost of antibiotics for catheter-associated UTIs.10 Reminders to remove unnecessary catheters can be issued by the nursing staff or by computerized ordering systems.5,10

Other educational interventions that have proven effective include education about prevention of compression of catheter leg tubing and compliance with handwashing protocols. In one interventional study of catheter-associated UTI rates in an adult intensive care unit, patients who were catheterized for at least 24 hours had significantly lower UTI rates during the educational intervention period than during the prior non-intervention observational period. After education was initiated, the rate of infection declined from 21.3 to 12.39 UTIs per 1000 catheter-days (P=0.006).11

Device and Product Interventions
In addition to practice intervention, the choice of catheters and related equipment can also reduce UTIs substantially. Other methods of catheterization should be considered before inserting an indwelling catheter. Catheterization options are based on the reason for catheterization and the expected duration of need. Other options include condom catheters for males, suprapubic catheters for patients who require long-term indwelling drainage, and intermittent catheterization for patients with spinal cord injuries.3,7 Patients who must use an indwelling catheter should have a closed catheter system with a small catheter (14 to 18 French with a 5-cc balloon). Manufacturer’s recommendations for inflation and deflation, system maintenance, securing the catheter, and properly positioning the drainage bag below the patient’s bladder should be followed. Preventing encrustation and blockage are also very important.9 Following these steps and properly maintaining closed drainage catheter systems has been shown to substantially reduce the risk for UTI.3

Recently, several catheters designed to discourage the growth and adherence of pathogens have been tested. A two-year prospective study in 10 patient care units was conducted to determine the efficacy of a silver alloy, hydrogel-coated urinary catheter in preventing catheter-associated UTIs. Secondary endpoints included cost analysis and monitoring the emergence of silver resistance in urinary microbial isolates. Historic data provided control information for comparison of infection rates before and after introduction of the new catheter. Use of the silver coated catheter produced a statistically significant reduction from 6.13 catheter-associated UTIs per 1000 catheter-days to 2.62 UTIs per 1000 catheter-days (P=0.002). Modest cost savings were noted, and no microbial resistance developed during the study.12 Other studies of the silver-hydrogel catheter also have reduced the expected rate of UTIs and appear to be particularly effective against gram-positive organisms, which generally enter the bladder extraluminally. Gram-negative bacteria typically enter the bladder intraluminally. Based on these data and other studies of the silver-hydrogel catheter, overall direct cost savings are estimated at $6,500 per 100 catheters.3 Studies of other types of catheters impregnated with nitrofurazone and a combination of minocycline and rifampin have produced significant reductions in catheter-associated UTIs, as well, but additional study is needed in larger patient populations.3

Conclusion
Reduction of catheter-associated UTIs is based primarily on preventive infection control practices. The cornerstones of effective prevention include thorough adherence to the guidelines promoted by the CDC for hand hygiene, correct insertion, handling, positioning, and maintenance of catheters; avoidance or limited use of long-term indwelling catheters; and possibly selection of catheters that are designed to deter biofilm growth. Following appropriate practice and product interventions, it is possible to significantly reduce the number of catheter-associated UTIs. This, in turn, reduces hospital stays and associated costs of treatment.

Additional study of the effects of biofilms as contributors to UTIs is necessary, along with further study of new catheter products, including silver alloy and antimicrobial-impregnated products. Initial results of these products have shown impressive cost savings. HPN