Expert Discusses Strategies to Prevent CAUTIs
ICT spoke with Rabih Darouiche, MD, professor and director of the Center for Prostheses Infection at Baylor College of Medicine, regarding strategies for preventing catheter-associated urinary tract infections (CAUTIs).
ICT: How do you define a CAUTI, and what do you believe is the scope and magnitude of the problem?
RD: This is a tremendous problem in terms of incidence, morbidity, potential mortality, as well as economic implications. In terms of incidence, we know that indwelling urinary catheters are responsible for almost 95 percent of all cases of nosocomial urinary tract infections (UTIs). And we know that about 30 million bladder catheters are inserted each year in the United States alone. It is estimated that probably a total of about 1 million cases of CAUTIs occur each year in this country. In fact, CAUTIs are the most common nosocomial infection that occurs in association with any type of an indwelling medical device.
In terms of medical complications, although most cases tend to involve only the lower urinary tract, in some populations even a minor episode of lower UTI may affect other aspects of their healthcare. For example, if you take hospitalized patients with spinal cord injuries who are admitted primarily for rehabilitation, and if such patients develop even a minor case of cystitis associated with an indwelling bladder catheter, then that will result in down time for rehabilitation, which means prolonged hospitalization.
Furthermore, about 5 percent to 10 percent of such cases of CAUTIs involve the upper urinary tract, causing polynephritis; those cases are the ones that may result in urosepsis, septicemia, and sometimes even death. The third impact of CAUTIs has to do with economical effects, such as prolonged hospitalization due to UTI, having to miss a number of days of work because of illness, or having to receive antibiotics, either intravenously or orally ... these factors all combine to produce a tremendous economic impact.
ICT: What is the cost of treating a UTI and of treating urosepsis?
RD: It depends on whether the patient is treated in the hospital or as an outpatient. It also depends on the type of organism(s) causing the infection. Generally, the average cost for treatment of a UTI as an outpatient, when using oral therapy, may not exceed a few hundred dollars. And it may even be cheaper if its caused by a multi-susceptible organism that could be treated by genericlabel oral antibiotics. However, because of the excessive unnecessary use of antibiotics, most cases of CAUTI are caused by resistant organisms, which have to be treated either with expensive oral drugs, or in some cases have to be treated with parenteral antibiotics because there are no available oral options that would provide coverage for those particular infecting organisms. For an inpatient case, you must add the overall costs of extended hospitalization, nursing care and parenteral antibiotics, and that is excluding the lack of productivity for patients who lose time from work. It can be very expensive, and most estimates are in the neighborhood of $2,000 per infection.
ICT: And the cost of urosepsis?
RD: Urosepsis by definition means that not only do you have a UTI, but that the patient has systemic effects of the infection. Most cost estimates to treat are in the range of $30,000.
ICT: Clearly, we can conclude that CAUTIs are both common and costly. How do uropathogens gain access in the catheterized patient?
RD: There are three main routes of entry of infecting pathogens. The most commonly observed one is when the organisms gain entrance into the urinary tract by originating from the junction between the urethral meatus and the external surface of the catheter. With prolonged catheter duration and therefore with more manipulation of the catheter by healthcare providers, then we tend to see more of the effects of the second route of entry, which is entry of contaminating organisms through the junction of the catheter and the draining tube. The third route of entry, which is not as common as the first two routes, is when you have bacterial contamination of the urinary drainage bag, particularly in patients in whom the drainage bag is kept at a level higher than the bladder, thereby allowing collected urine, which contains bacteria, to drain back into the bladder, thereby resulting in bacteriuria and eventually UTI.
ICT: Which organisms most commonly infect via these various routes?
RD: The most common organisms are the grand negative bacteria and the Enterococci. These organisms are most common because they are components of the bowel flora and because of the proximity of the rectum to the urethral meatus; the skin and adjacent to that area is likely to be colonized by those infecting pathogens. Unlike in the case of vascular catheters where the infecting skin organisms are mostly staphylococci, in the case of CAUTIs, staphylococci only rarely cause UTIs.
ICT: We hear a lot these days about bacterial biofilms. Do such biofilms play a role in CAUTIs?
RD: All cases of device related infections are biofilm related; the reason is because within a short period of time after insertion of any foreign device, a combination of host factors, like fibrin, fibrinectin, fibrinogen, platelets and other host products, combine with bacterial organisms and their own products, to form the layer of mature biofilm. That layer of biofilm will form whether the catheter is inserted into the urinary system, the vascular space, the ventricular space, or any other area in the human body.
ICT: Does the presence of a urinary drainage catheter, eventually coated as you suggest with bacterial biofilm, always result in a bacteriuria?
RD: It depends on the type of the catheter and the duration of catheter placement. For example, in patients with chronic indwelling of bladder catheters, the longer the duration the more likely they will develop bacteriuria, which means just bacteria in the urine. For example, if you take catheters that have been in place for a week or longer, the likelihood of having bacteriuria by then is probably about 90 percent.
ICT: Does bacteriuria represent a disease state requiring treatment?
RD: I think that is an extremely important issue, which unfortunately has clouded the evaluation of measures that could potentially prevent CAUTIs.
Bacteriuria simply means a presence of bacteria in the urine. Most patients with an indwelling bladder catheter will have bacteriuria. Most cases of bacteriuria will remain asymptomatic. Only a small percentage depending on the type of patient and duration of catheter placement, and perhaps even the type of organisms responsible for the bacteriuria, because some of them are more virulent than others become symptomatic. I would say anywhere between 10 percent and 30 percent of cases of bacteriuria will become associated with a clinical episode of CAUTI. That is very important to comprehend because the primary objective in coming up with an optimal solution for CAUTI is to prevent this infection rather than to prevent bacteriuria. In fact, you may not be able to prevent bacteriuria. Moreover, even if you decrease the incidence of bacteriuria, there is no guarantee that that decrease in the incidence of bacteriuria will result necessarily in the reduction in the rate of CAUTI.
ICT: The Occupational Safety and Health Administration (OSHA) frequently refers to work-practice controls and engineering controls. Work practice controls mean primarily methods of use, measures that one can take in the course of daily practice. Engineering controls refer to products. Are there work practice controls habits of use, technique that can be implemented that in and of themselves can diminish the risk of CAUTIs?
RD: In my opinion, the most important work practice control for prevention of CAUTI is to avoid inappropriate catheterization and to remove the catheter when no longer clinically indicated. Unfortunately, studies have shown that we have not done very well with either of these two issues, because still a significant portion of catheter insertions are deemed improper, and because we as physicians often are not even aware that our own patients have an indwelling catheter. Even in instances where we are made aware of the existence of a bladder catheter in our own patients, we may not effectively consider alternatives to catheterization; for example, an external condom or other voiding measures. In terms of nurses input, the most important preventive measure is to provide optimal sterile techniques at the time of insertion, as well as during maintenance of the indwelling bladder catheter. Unfortunately, I think we probably have reached a point of maximum return from optimizing those work habits. Therefore, we get to a point where we should look for other options that may augment those work habits.
ICT: Can you give us an overview of the various technologies and engineering controls that have been applied to the reduction and eradication of CAUTIs?
RD: By relying on what we know now, we have to admit that we cannot completely eradicate or prevent the formation of the biofilm around the bladder catheter. Therefore, our technological advancements should be based on manipulation of the biofilm in one form or another in an attempt to prevent that biofilm from triggering clinical infection. Theoretically, technology can achieve that objective via one of three forms. The first form is to use drugs to fight bugs, and that form can be provided in three fashions. The first fashion is via systemic administration of anti-microbial agents in an effort to prevent recurrent bouts of symptomatic UTI. In that regard, clinical trials have shown that although systemic, long-term systemic antimicrobial prophylaxis may reduce the rate of UTI due to that particular agent or agents, that comes at the expense of a higher rate of infection due to more resistant organisms. Therefore, with systemic prophylactic antibiotics, the overall rate of CAUTI is not reduced. Additionally, systemic antibiotic prophylaxis is associated with adverse drug effect and allergic reactions. Therefore, because of the relatively poor efficacy and the concern over safety and toxicity, this practice is largely abandoned.
The second vehicle by which we can use drugs to fight bugs is to administer them locally, as in application to the urethral meatus, irrigation of the bladder catheter or the bladder itself, and addition of anti-microbial agents to the urinary drainage bag. Clinical trials that have assessed all of these measures have produced conflicting or ineffective results.
That leaves us with the third vehicle by which drugs can be used to prevent bugs, which is the incorporation of antimicrobial agents onto the surface of the catheter. Unlike in the case of vascular catheters where the catheter surface that is surrounded by relatively small numbers of bacterial colony counts and the skin surrounding the exit site is potentially subject to strong protection by certain forms of anti-microbial coatings in the context of bladder catheters, the results have not been satisfactory. Particularly in the area of chronic indwelling bladder catheters, where to my knowledge there have been no prospective randomized clinical trials that have shown that a particular type of antimicrobial coated bladder catheter has reduced the rate of infection not asymptomatic bacteriuria, but symptomatic infection as compared with an controlled uncoated catheter. Even in the context of short-term catheterization of patients for one, up to two weeks, the clinical efficacy has been largely based on the results of prospective, non-randomized clinical trials, be it prospective cohort, or prospective crossover studies. And therefore, the true efficacy of those coated catheters in preventing catheter associated urinary tract infection still needs to be determined through better-designed prospective, randomized clinical trials.
The second form of technologic advancement can be based on using bugs to fight bugs. Knowing that bugs are very smart, they are more likely to adapt to situations that may be harmful to them. Therefore, it may be reasonable to utilize that bacterial property to our advantage. For example, we all harbor organisms in our bodies that are not pathogenic, and those organisms in our mouth and in our bowels may compete with pathogens.
That constitutes a passive form of bacterial interference. So, healthcare providers may opt to use another form of bacterial interference, that of active bacterial interference, where we intentionally introduce nonpathogens into the human body in an effort to compete with pathogens.
We have studied this over the last 10 years and we have been able to introduce a non-pathogenic strain of E. coli into the bladder of patients with spinal cord injury who have had frequent episodes of UTI. And both in a small prospective open label clinical trial as well as in a small prospective randomized placebo control evaluated blinded clinical trial, we were able to demonstrate that this approach of active bacteria interference does reduce the rate of infection. This prompted us to initiate an ongoing prospective randomized, multi-center, placebo-controlled, evaluator-blinded clinical trial sponsored by the National Institutes for Health.
The third form of technologic advancements that may affect the ability of the biofilm to result in clinical infection is an innovative securement device, which is intended to reduce the likelihood of discordant motion between the catheter and the human tissue thereby discouraging or blunting the migration of organisms along the catheter surface. This device may also reduce the likelihood of traumatizing the inner human tissues which form a natural barrier against infection. And we all know that a healthier, less traumatized tissue will probably be more able to resist clinical infection when exposed to bacteria as compared to a more diseased and less healthy tissue. A prospective randomized clinical trial has indicated that the use of a securement device called Statlock, in the context of inserted PICC lines, showed significant protection against catheter-related bloodstream infection as compared with the control suture technique. Taking that into consideration, we recently completed a prospective, randomized, multi-center clinical trial that assessed the efficacy of the Statlock device in preventing a UTI in spinal cord patients with indwelling bladder catheters as compared with other traditional securement measures such as using a tape, gauze, a Cath-secure, or even no securement. The results showed a remarkable 45 percent reduction in the rate of CAUTI; remember, this is symptomatic infection in those whose bladder catheters were secured by using the Statlock device.
ICT: Were the findings of this Statlock study both clinically and statistically significant?
RD: As I have mentioned, there was a 45 percent reduction in the rate of clinical catheter associated urinary tract infection. That study, however, was not sufficiently powered to show statistically significant differences. But the trend was very strong, and a 45 percent reduction in clinical infection which was the primary outcome in that study is very clinically relevant. Furthermore, this is the only prospective randomized clinical trial that has shown such a relatively high degree of protection against CAUTI without using antimicrobial agents, which theoretically can have a number of potential drawbacks, including toxicity, allergic reactions and potential for development for antibiotic resistance.
ICT: What measures then would you now take to prevent or limit CAUTIs in patients with both short-term and long-term indwelling Foley catheters?
RD : In patients with short-term indwelling bladder catheters, I think the most effective approach would be to prevent inappropriate catheterization to start with; to become more aware of the existence of those bladder catheters in our own patients; and then, to act upon that information once obtained by considering an alternative to bladder catheterization.
In patients with long-term indwelling bladder catheters, it is important to rely more on technological advances. In either case, I think its important to consider technologic advances that have been found in prospective randomized clinical trials to produce clinically relevant reduction in the rate of CAUTI. In that regard, we know that the Statlock securement device has been found to produce a very clinically relevant reduction in the rate of infection associated with long term in dwelling bladder catheters. Although no studies have been done in the context of short-term catheters, because the mechanism of infection is essentially the same, the use of StatLock in that population should be considered as well. As far as antimicrobial-coated catheters, I am not aware of any studies that have shown efficacy in long-term bladder catheters. Their studies have been largely applied to short-term bladder catheters. So although such coated catheters may be considered for use for short-term bladder catheterization, there is no guarantee that they will be protective for long-term bladder catheterization.
ICT: Theres a great deal of evidence looking at the efficacy of catheter coatings. What is the greatest limiting factor in those studies?
RD: I think the primary limitation of those studies, of the vast majority, is that they have considered the mere existence of bacteriuria as a primary outcome. Whereas we know that the only important clinical outcome should be symptomatic UTI. And therefore if a study, even if well-designed, showed a reduction in the rate of bacteriuria, it may not necessarily guarantee that a simultaneous reduction in the rate of clinical CAUTI will be observed as well.