Technology vs. the Most Common Nosocomial Infection
By Sandra K. Watson, RN, BSN, CIC; Deborah Ann Lichtenberg, RN, BSN, CIC; and Holly Wainwright, RN, BSN, MBA, CIC
Figure 1: Electron micrograph of Pseudomonas aeruginosa after two hours on a 100% silicone foley catheter.
As most hospital infection control programs begin their fifth decade of existence, the rising acuity of patients has more than offset gains in lowering the rate of hospital-acquired infections. In the last 20 years, the rate of noscomial infections has increased 36% to 9.8 infections per 1000 patient days.1 Except for the widespread adoption of the closed system, no new behavioral interventions have been shown to have an enduring effect on the prevention of the most frequently occurring nosocomial infections--urinary tract infections (UTIs). For decades, experts have tried to develop reliable and proven technologies to reduce the incidence of UTIs with limited success--until very recently. Today, several technological advancements in surface coatings on the indwelling, or Foley, catheter have been studied and have been found to reduce the occurrence of nosocomial UTIs. In the current healthcare environment, which emphasizes cost benefit and cost avoidance, infection control professionals are challenged to improve clinical outcomes such as catheter-associated UTIs (CAUTIs) while conserving resources. Evaluating new technology may help clinicians to meet this challenge. This sentiment is expressed by one of the nation's foremost infection control authorities, Robert A.Weinstein, MD, who notes, " Given the choice of improving technology or improving human behavior, technology is the better choice."2
The Significance of UTIs
CAUTIs contribute to antibiotic resistance, delay a patient's recovery, and increase healthcare costs. According to the Centers for Disease Control and Prevention, UTIs are the most commonly reported nosocomial infection in the US, accounting for approximately 40% of all hospital infections. Nosocomial UTIs (NUTIs) cost the nation's hospitals $1.8 billion annually.3 Foley catheter use is associated with 80% to 90% of these hospital-acquired infections.4 NUTIs are also noted to be the second most common infection in critical care units.5
At the 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections, held in Atlanta in March 2000, Dennis Maki, MD, one of the world's most respected infection control researchers, noted that 25% to 40% of patients in any given hospital have a urinary catheter and about 15% to 50% of those patients will develop a UTI as a result of that catheter.4,6 Maki stated that the urinary tract is a source of VRE, resistant gram negatives, and yeast, which can easily be transmitted from patient to patient. "I don't think there's any larger reservoir of antibiotic resistant organisms in hospitals," stated Maki.4
Length of stay for patients with NUTIs may be increased from 1 to 3.8 days. Per case costs may range from $676, a minimum estimate for a symptomatic but uncomplicated UTI, to an average of $3,803 based on a case control study that determined attributable cost differences.7,8,9
Urinary Tract Infections: The Role of the Catheter
The indwelling urinary catheter, or Foley catheter, disrupts the normal defense mechanisms of the body. The Foley catheter is a conduit into the bladder and provides an open and continuous route for bacteria to ascend along the walls of both the internal and external surfaces of the catheter.10 Additionally, the retention balloon prevents complete emptying of the bladder, resulting in a small amount of residual urine in which microorganisms can multiply and increase the chance of infection.
The surface of the catheter plays an important role in the development of CAUTIs. Bacteria that colonize both the inner and outer surfaces of the catheter grow in microcolonies within a biofilm.10 Once this biofilm has been established, it will then migrate in all directions along the catheter surfaces.11 The bacteria within this biofilm are protected from the activity of antibiotics, making treatment difficult. In a recent presentation made to the 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections, Maki stated, ". . . anti-infective surfaces, hold the greatest promise for materially reducing the risk of infection with indwelling catheters." 6
Early Foley Catheter Technology
The first latex catheter was developed in 1929 by Dr. Frederick E. B. Foley (1891-1966). It was a soft, rubber catheter used to control hemorrhage following transurethral prostatectomies.12 Latex was an obvious choice for catheter material due to its durability and properties of strength, flexibility, and elasticity. Originally, latex catheters received a surface treatment with chlorination to help them appear and feel smoother.
In the 1960s, Teflon®-coated latex catheters were developed. These catheters improved ease of insertion and comfort for the patient. They also increased the length of time the catheter could provide continuous drainage of urine without encrustation. In the 1970s, a 100% silicone catheter was introduced with the intention that it would be less irritating to the bladder and urethra and would inhibit encrustations. Silicone catheters tend to have thinner walls and slightly larger lumens to allow for better drainage of urine. They are also stiffer than a latex catheter and exert a static charge that attracts debris. These catheters are typically more expensive than latex catheters and tend not to provide the average patient with any added benefits. Furthermore, all-silicone catheters are very susceptible to rapid bacterial colonization and migration (Figures 1 and 2).
To overcome the expense and stiffness of an all-silicone Foley catheter, a silicone elastomer-coated latex catheter was released that incorporated the flexibility and strength of latex and the durability and reduced encrustrations typical of 100% silicone catheters.11 Catheters made of Teflon-coated latex and silicone elastomer-coated latex were introduced with the hopes of improving compatibility between patient and catheter, but there has been little evidence to demonstrate that less irritation and inflammation in the urethra occurred with these catheters over those constructed of uncoated latex.13
In the 1980's, hydrogel coatings were introduced to reduce bacterial adherence to the catheter surface and to reduce the coefficient of friction between the catheter surface and the urethral mucosa.14 Hydrogel acts to form a "hydrated cushion" that attracts water to the surface of the catheter and helps it to "float" within the walls of the urethra. This mechanism results in easier insertion and less potential for irritation and infection.
Foley Catheter, "Active" Part of IC
The most recent developments with Foley catheter surfaces center on the application of antimicrobial or antiseptic coatings. The first attempt at an antimicrobial coating involved the use of a silver compound. Silver has a long history in the field of medicine and has been studied in many forms and applications. It is one the first metals known to posses antimicrobial properties at low concentrations and has a low incidence of bacterial resistance. In the late 1980s, a silver compound in the form of silver oxide was applied to the external surface of Foley catheters. Riley reported in a large randomized trial that the silver-oxide coated Foley catheter failed to demonstrate efficacy in the prevention of catheter-associated bacteruria.15 Additionally, the coating was reported to come off and left the patient with a discoloration around the meatal and perineal area. This catheter is no longer manufactured.
A unique technology, developed in 1994, employs the use of silver alloy to coat both latex and silicone urinary catheters. These catheters contain a thin monolayer of colloidal silver, which is applied to both the inner and outer surfaces of the catheter and is then coated with a permanent layer of hydrogel. The thin layer of silver creates an effective mechanism for the release of silver ions that are known to be toxic to bacteria.14 The colloidal silver inhibits the ability of bacteria to attach, multiply, and migrate on catheter surfaces decreasing the risk of infection.The hydrogel coating reduces urethral trauma and helps preserve the natural infection fighting mechanisms of the urethral mucosa. The advantages of combining silver alloy and hydrogel include the lack of microbial resistance to colloidal silver and biocompatibility in both adults and children.11 Silver and hydrogel coating technology has also been applied to an all-silicone catheter to offer an antimicrobial Foley catheter option for those patients for whom a latex-based catheter may be contraindicated.
Many trials have been conducted showing that silver alloy-coated catheters are significantly more effective in reducing UTIs than other types of coated and uncoated catheters. A meta-analysis by Saint of eight clinical trails demonstrated that silver alloy-coated indwelling catheters were significantly less likely to be associated with the development of bacteriuria than non-silver alloy-coated catheters. In a separate economic analysis of the silver alloy-coated catheter, Saint concluded that although the silver alloy-coated catheters cost more than a standard catheter, it saved more than it cost by reducing the costs of nosocomial catheter-related infection and bacteremia.17 Saint's meta-analysis associated the use of silver alloy catheters with a 45% reduction in the incidence of symptomatic UTI and 51% relative decrease in the incidence of bacteremia. The conclusion made by Saint was that consideration should be given to the use of silver alloy-coated catheters in hospitalized patients requiring catheterization for 3-7 days.18
Figure 2: Electron micrograph of Pseudomonas aeruginosa after 18 hours on a 100% silicone foley catheter.
Lettau et. al. conducted a study of the silver alloy-coated Foley catheter in nine community-based hospitals. Lettau determined the rate of NUTIs over a six-month period of time, resulting in a 55% decrease in the incidence of UTI with use of the silver alloy-coated catheter. It was concluded that individuals hospitalized for short-term stays represented the patient population that could best take advantage of silver alloy-coated catheters to prevent UTIs.19
In one of the largest device trials conducted to date, Maki and colleagues found in a randomized, double-blind study involving over 850 catheterized patients that the silver alloy-coated catheters provided substantial protection against CAUTI for up to 20 days with approximately 30% reduction in risk. They concluded that the greatest benefit was for preventing CAUTI caused by gram positive organisms and yeast. The catheter was well tolerated by patients with no attributable side effects or complications. It did not select for CAUTI caused by silver resistant bacteria and was shown to be cost beneficial.6
Recently, a novel, all-silicone Foley catheter, coated with an antimicrobial drug, was released. This catheter is designed to block bacterial entry along the catheter-urethral interface and incorporates the antimicrobial agent Nitrofurazone. Nitrofurazone is broadly active against many gram positive and gram negative bacteria and has been used extensively in medicine. The initial results of the clinical trials showed that the catheter was well tolerated by adult patients and provided quantifiable surface activity for up to seven days. Maki, et. al., studied this product in a randomized, investigator-blinded trial of 344 catheterized patients and found a decrease in UTIs within the first seven days of catheter use. After seven days of use, the catheter did not appear to provide protection and was not effective for long-term catheterization. It was also noted that the Nitrofurazone coated catheter failed to provide a statistically significant reduction in infections caused by Candida, Enterococcus, or other Nitrofurazone-resistant organisms.20 Another limited study of 30 burn patients found a reduction in UTIs. However, the incidence of Candida albicans increased three-fold.21 Some members of the medical community have expressed their concern that the use of drug compounds on devices may contribute to the development of antimicrobial resistance due to the continuous prophylactic release of antibiotics. Healthcare professionals must employ discretion with the use of Nitrofurazone-coated Foley catheters because of precautions concerning their use in children, pregnant women, nursing mothers, and individuals with sensitivity to nitrofurazone (1.2 % of patients treated with topically administered Nitrofurazone exhibit sensitization and generalized allergic reaction).22
There continues to be ongoing research and development aimed at surface technologies of catheters. Some new coatings being investigated include conductive polymers and metals to create a controlled electrochemical release of silver ions.23 Another method to deter the adherence of bacteria to the catheter surface uses the polysaccharide, hyaluronan due to its lubricious and hydrophilic properities.24 Other coatings have also included salicylic acid and also the antibiotic ciprofloxacin.25
A comprehensive review of the available literature, indicates that technology is the direction in which medical advancements are being made. In spite of the dramatic advances offered by currently available antimicrobial-coated Foley catheters, there remains considerable opportunity to further reduce the incidence of NUTIs. In a recent presentation, Maki stated that progress is finally being made in what he thinks is the most challenging device-related infection there is.6
As the twenty-first century unfolds, the challenge to healthcare researchers will be to continue to develop better methods to prevent UTIs. In the new millennium, infection control practitioners must continue to seek multiple approaches that are directed toward augmenting "technique" with "technology" to improve clinical outcomes. Lastly, infection control practitioners must recognize the impact that their initiatives can make toward reducing the economic pressure of today's healthcare arena by following the guidance of Saint who stated, "Given the clinical and economic burden of urinary catheter-related infection, infection control professionals and hospital epidemiologists should use the latest infection control principles and technology to reduce this common complication".
Sandra K. Watson, RN, BSN, CIC is a Infection Control Clinical Specialist, Bard Medical Division (Covington, Ga); Deborah Ann Lichtenberg, RN, BSN, CIC, is a Infection Control Clinical Specialist, Bard Medical Division; and Holly Wainwright, RN, BSN, MBA, CIC, is a Infection Control Clinical Specialist, Bard Medical Division.
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What about Multidrug-resistant Bacteria?
By James Carper
The emergence of multidrug-resistant bacteria is a major concern in hospitals today. To address the problem, infection control professionals are updating and implementing policies aimed at both containing the spread of these bacteria and promoting more prudent use of the antimicrobial agents used to prevent and treat nosocomial infections. One such infection, catheter-associated urinary tract infection (CAUTI), has become recognized as a major reservoir of multidrug-resistant bacteria. Consequently, hospitals are giving an increased priority to efforts to prevent CAUTIs. Reducing the occurrence of CAUTI caused by multidrug-resistant bacteria also reduces the chance of spreading these types of infections. Moreover, when the initial occurrence and spread of bacterial infection are reduced, overall usage of systemic antibiotics can be lowered, thus helping reduce the development of resistance to those antibiotics.
Among the solutions available for dealing with this problem are technologically advanced products that have been shown to reduce the incidence of CAUTI significantly. Ideally, such new products will reduce the incidence of these infections, reduce usage of systemic antibiotics, and allow integration into hospital care without major interruptions to accepted practices. One product that is proving to meet all these requirements is the Release-NF® controlled-release nitrofurazone Foley catheter manufactured by Rochester Medical Corporation. Designed to reduce catheter-associated bacterial urinary tract infections, this catheter has more recently been shown to have a high level of in vitro activity against many of the types of multidrug-resistant bacteria that are associated with hospital-acquired urinary tract infections, including MRSA.1
This latex-free Foley catheter is active against a broader range of bacteria than catheters using silver coating technologies and, unlike other antimicrobial catheters that are intended to prevent colonization on its surface, the Release-NF catheter delivers the antiseptic nitrofurazone directly to the patient's urethra. Because the nitrofurazone is not systemically absorbed, the catheter can provide site-specific antibacterial prophylaxis that can be used without concern for interactions with systemic antibiotic treatments.
Will using Release-NF catheters create bacteria that are resistant to nitrofurazone? Nitrofurazone is an antiseptic with over 50 years of proven efficacy. It is a chemosynthetic compound whose kill mechanism is different than organically derived antibiotics. This may account for the lack of acquired resistance over many years of use. The site-specific use of Nitrofurazone provides a means for slowing the possibility of increased resistance to the major antibiotics customarily used for treatment of infections. It is those drugs, not Nitrofurazone, that are of great concern for the development of further resistance. Because the Release-NF catheter targets the delivery of the antiseptic to a very small area, it will likely reduce total drug usage by reducing the need to systemically treat CAUTIs. In contrast, each UTI treated with systemic antibiotics fosters ideal conditions for the development of further resistance by exposing low levels of antibiotic to the bacteria that flourish in the bowel.
The Release-NF catheter has been shown to reduce nosocomial bacterial UTIs. It is used as a traditional Foley catheter, yet has been shown to be active against many types of MDR bacteria. In the current era of emerging multidrug-antimicrobial resistance, the Release-NF catheter is a means of combating the important problem of multidrug-resistant bacteria. Its is a well-targeted local antibacterial technology that will help prevent CAUTI and likely reduce the usage of systemic antibiotics and their contribution to multidrug-resistant bacteria problem.
1. Johnson JR et al. Activities of a Nitrofurazone-containing urinary catheter and a silver hydrogel catheter against multidrug-resistant bacteria characteristic of catheter-associated urinary tract infection. Antimicrob Agents Chemother. 1999;43(12): 2990-2995.
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