Liquid Chemical Germicide Research Articles

High-level disinfection of gastrointestinal endoscope reprocessing.

High level disinfection (HLD) of the gastrointestinal (GI) endoscope is not simply a slogan, but rather is a form of experimental monitoring-based medicine. By definition, GI endoscopy is a semicritical medical device. Hence, such medical devices require major quality assurance for disinfection. And because many of these items are temperature sensitive, low-temperature chemical methods, such as liquid chemical germicide, must be used rather than steam sterilization. In summarizing guidelines for infection prevention and control for GI endoscopy, there are three important steps that must be highlighted: manual washing, HLD with automated endoscope reprocessor, and drying. Strict adherence to current guidelines is required because compared to any other medical device, the GI endoscope is associated with more outbreaks linked to inadequate cleaning or disinfecting during HLD. Both experimental evaluation on the surveillance bacterial cultures and in-use clinical results have shown that, the monitoring of the stringent processes to prevent and control infection is an essential component of the broader strategy to ensure the delivery of safe endoscopy services, because endoscope reprocessing is a multistep procedure involving numerous factors that can interfere with its efficacy. Based on our years of experience in the surveillance of culture monitoring of endoscopic reprocessing, we aim in this study to carefully describe what details require attention in the GI endoscopy disinfection and to share our experience so that patients can be provided with high quality and safe medical practices. Quality management encompasses all aspects of pre- and post-procedural care including the efficiency of the endoscopy unit and reprocessing area, as well as the endoscopic procedure itself.

Infection control during GI endoscopy

This is one of a series of statements discussing the use of GI endoscopy in common clinical situations. The Standards of Practice Committee of the American Society for Gastrointestinal Endoscopy (ASGE) prepared this text. In preparing this guideline, a search of the medical literature was performed by using PubMed, supplemented by accessing the "related articles" feature of PubMed. Additional references were obtained from the bibliographies of the identified articles and from recommendations of expert consultants. When little or no data exist from well-designed prospective trials, emphasis is given to results from large series and reports from recognized experts. Guidelines for appropriate use of endoscopy are based on a critical review of the available data and expert consensus at the time the guidelines are drafted. Further controlled clinical studies may be needed to clarify aspects of this guideline. This guideline may be revised as necessary to account for changes in technology, new data, or other aspects of clinical practice. The recommendations were based on reviewed studies and were graded on the strength of the supporting evidence (Table 1). This guideline is intended to be an educational device to provide information that may assist endoscopists in providing care to patients. This guideline is not a rule and should not be construed as establishing a legal standard of care or as encouraging, advocating, requiring, or discouraging any particular treatment. Clinical decisions in any particular case involve a complex analysis of the patient's condition and available courses of action. Therefore, clinical considerations may lead an endoscopist to take a course of action that varies from these guidelines.

Recent advances in epidemiology and prevention of gastrointestinal endoscopy related infections

This article reviews recent publications relevant to endoscope reprocessing and the potential for transmission of infection during gastrointestinal endoscopy. There have been a number of established reprocessing failures of gastrointestinal endoscopes at various healthcare facilities across the US resulting in patient notifications. These episodes have been associated with user errors and reprocessing equipment failures, highlighting the need for increased compliance with established guidelines. Surveillance cultures may be useful to monitor the outcome of reprocessing, although their use is controversial. New technology to allow point-of-use monitoring is promising. Biofilm accumulation may be an issue when reprocessing gastrointestinal endoscopes. Although peracetic acid has been promoted as superior to aldehyde-type liquid chemical germicides with regard to soil fixation, it may only be a modest improvement. Electrolyzed acid water is an emerging liquid chemical germicide that may be equivalent to currently accepted disinfectants. There appears to be no benefit to an additional reprocessing cycle before use for endoscopes that have been appropriately cleaned, disinfected, and stored. With the recent media attention on gastrointestinal endoscope reprocessing failures, despite the absence of documented transmission of infection, increased compliance with existing guidelines and new initiatives to enhance endoscope reprocessing are increasingly important to maintain public confidence.

Transmission of infection by gastrointestional endoscopy: May 2001

Transmission of infection by gastrointestional endoscopy: May 2001

Culture Age and Drying Time as Variables of the AOAC Sporicidal Test

In the United States, the AOAC Sporicidal Activity of Disinfectants Method 966.04 is the standard for identifying a liquid chemical germicide as a sterilant. Furthermore, the highest level of a disinfectant must also be a sterilant as defined by Method 966.04, when used in its sterilant mode for a longer exposure time. The AOAC Sporicidal Test is also used as a part of the standard test methods to define a sterilant for Australia and the European Union. Many laboratories have identified variables of this test that can affect the sterilization exposure time for sterilants, or even the ability to classify a chemical as a sterilant. Method 966.04 requires spore-labeled porcelain penicylinders (cylinders) and silk suture loops, collectively referred to as carriers, to be dried for 24 h, but allows these carriers to be used for at least 7 days, in effect allowing a drying time of 24 h to at least 7 days. We tested the resistance of cylinders that had been labeled with Bacillus subtilis spores cultured for 72, 96, and 120 h, and dried for 24, 48, and 72 h against a 60 min exposure to 2.0% alkaline glutaraldehyde, and 2, 5, 10, 15, and 20 min exposures to 2.5N HCl. All the culture incubation and drying times met the standard of resistance to 2.5N HCI for at least 2.0 min at 20 degrees C, and all carriers contained at least 10(5) colony-forming units (CFU) of B. subtilis per carrier. However, for 3 repeated tests, regardless of incubation time, an average of 96% of the carriers were sterilized by the 2.0% glutaraldehyde after drying for 24 h, and an average of 61 % were sterilized after drying for 48 or 72 h. We propose that the variable of drying time be eliminated from Method 966.04.

Glove resistance to permeation by a 7.5% hydrogen peroxide sterilizing and disinfecting solution

Background: This study evaluated 6 types of glove materials for resistance to permeation by a 7.5% hydrogen peroxide liquid chemical germicide. Methods: Based on American Society for Testing and Materials Method F739-96, a small piece of glove material was placed in the center of a dual chamber test cell. The challenge and collection chambers of the test cell were filled with the hydrogen peroxide test chemical and the collecting medium (deionized water), respectively. Chemical permeation was determined by measuring the concentration of hydrogen peroxide in the collection medium at various time intervals. Results: Both the polyvinylchloride and disposable latex examination gloves at 4.5 mil thickness provided less than 30 minutes of protection from hydrogen peroxide. The natural rubber latex glove at 16.5 mil lasted for 8 hours without any detectable penetration. Neoprene (15 mil) and nitrile butyl rubber (18 mil) both provided excellent protection throughout the 8-hour test period. Conclusion: Disposable latex examination gloves should be used for short-term exposure to hydrogen peroxide solutions. Thicker rubber latex gloves provided adequate protection and necessary dexterity for conducting intricate tasks. The level of protection depends largely on the thickness and quality of the glove material. (AJIC Am J Infect Control 1999;27:364-6)

Principles To Guide International Standard Tests for Liquid Chemical Germicides: A Proposal

This review discusses issues involved in developing standard tests for liquid chemical germicides and suggests some guiding principles to be considered for future development of harmonized international standard methods for testing disinfectants and sterilants. A published test method to measure sporicidal activity is used as an example of the implementation of these principles.

Modified quantitative association of official analytical chemists sporicidal test for liquid chemical germicides

The Association of Official Analytical Chemists (AOAC) test for sporicidal activity of disinfectants (966.04) is used in the United States as the legal criteria for classifying a liquid as a chemical sterilant and also as the indicator of the highest level of disinfectant. This qualitative test contains procedures that may cause inaccurate results. A modified, quantitative version of the AOAC sporicidal test has been developed that uses a specified minimum number of spores (2.0 x 10(sup5)) of Bacillus subtilis or Clostridium sporogenes dried onto porcelain penicylinders. This modified test was validated with three commercial sterilant chemicals tested on three separate groups of spore-labeled cylinders.

Comparative sporicidal effect of liquid chemical germicides on three medical devices contaminated with spores of Bacillus subtilis

Background: The relatively limited variety of surfaces and geometries challenged in current sporicidal testing reduces the predictive value of these analyses when extrapolated to the wide variety of medical devices. The unknown spore load being challenged and the qualitative nature (growth/no growth) of those tests further prevent precise comparison among liquid chemical disinfectants. Hence, the relative activity of different chemical substances has not been clearly established, hindering selection of the best agent for each clinical situation. Methods: A micromethod was developed to assess sporicidal activity against Bacillus subtilis spores deposited on three different medical devices: carbon-steel dental burs silicone-rubber medical catheters, and titanium-alloy dental abutment screws. The spore load on each device and the recovery after three analytical steps were quantitatively assessed with spores radiolabeled with carbon 14 menthionine. Results: The killing of 2 to 7 × 10 6 spores loaded on three different devices and exposed to glutaraldehyde, fomaldehyde, copper ascorbate, hydrogen peroxide, peracetic acid, sodium hypochlorite, or phenol for 30 minutes at 20° C ranged from a 10 3-fold decrease for 10% hydrogen peroxide to zero decrease for 5% phenol. Our results suggest that the nature of the surface being challenged may affect the sporicidal activity of some chemical agents. Conclusion: The quantitative data presented allow comparison of the sporicidal effect of different liquid chemical agents. These findings may help prevent an overestimation of sporicidal activity and possible transmission of pathogens from the surface of improperly decontaminated medical devices.

Advantages and limitations of automatic flexible endoscope reprocessors

The advantages and limitations of automatic flexible endoscope reprocessors (AFERs) are presented. These medical devices can increase patient safety and minimize personnel exposure to the liquid chemical germicide and its vapors. Some models feature a printer to document important reprocessing parameters, an in-line tap water filtration system to reduce the likelihood of endoscope (and patient) contamination, and a heater to satisfy the elevated temperature requirements of some liquid chemical germicide labels. Although they offer significant advantages compared with manual reprocessing, AFERs have their limitations. Current models do not automate every endoscope reprocessing step and are not typically designed to reprocess every endoscope channel. Some AFER models may have to be periodically decontaminated to ensure that their internal components do not support microbial colonization. Moreover, their cost per cycle can be considerably more than manual reprocessing without necessarily reducing overall reprocessing time. Its limitations notwithstanding, an AFER is likely to be an asset in a busy endoscopy center. In addition to comparing automated and manual reprocessing, this article addresses important reprocessing issues and purchasing concerns.

High-Level Disinfection or “Sterilization” of Endoscopes?

Controversy has surrounded the use of liquid chemical germicides to reprocess medical instruments that are damaged by heat sterilization. A review of the literature was performed to assess and compare the efficacy of disinfection and sterilization processes. The results of this review demonstrate that high-level disinfection of thoroughly cleaned endoscopes is not associated with a higher infection rate than is "sterilization". While there may be a theoretical distinction between the highest level of disinfection and sterilization, thorough cleaning eliminates clinical differences between the two. High-level disinfection is quick, effective, inexpensive, and recommended whenever heat sterilization is not feasible. A low-temperature sterilization process should be considered only if it is comparable in cost to disinfection or if it offers demonstrated advantages without damaging the instrument. Neither disinfection nor sterilization is likely to be effective if the instrument is not cleaned thoroughly after use.

High-Level Disinfection or “Sterilization” of Endoscopes?

AbstractControversy has surrounded the use of liquid chemical germicides to reprocess medical instruments that are damaged by heat sterilization. A review of the literature was performed to assess and compare the efficacy of disinfection and sterilization processes. The results of this review demonstrate that high-level disinfection of thoroughly cleaned endoscopes is not associated with a higher infection rate than is “sterilization.” While there may be a theoretical distinction between the highest level of disinfection and sterilization, thorough cleaning eliminates clinical differences between the two. High-level disinfection is quick, effective, inexpensive, and recommended whenever heat sterilization is not feasible. A low-temperature sterilization process should be considered only if it is comparable in cost to disinfection or if it offers demonstrated advantages without damaging the instrument. Neither disinfection nor sterilization is likely to be effective if the instrument is not cleaned thoroughly after use.

Microbiologic Considerations: Disinfection and Sterilization Strategies and the Potential for Airborne Transmission of Bloodborne Pathogens

Bloodborne pathogens are transmitted from person to person by sexual contact and by injection of drugs and, in health-care settings, by needlesticks and, in the case of HBV, by mucous membrane exposure. Conventional disinfection and sterilization and housekeeping strategies are sufficient for the environmental control of bloodborne viruses. Environmentally mediated infection transmission of bloodborne viruses is unlikely and only HBV, because of the extraordinarily high viral concentration in blood, is thought to have a real potential for such transmission. No epidemiologic or laboratory data support the hypothesis that surgeons or other health care workers are at increased risk of infection by bloodborne pathogens. Although theoretically possible, airborne transmission does not appear likely. Studies that claim to show the potential for airborne transmission of bloodborne pathogens ignore the basic principles of aerobiology and the requirements for proving environmental transmission.

FDA labeling requirements for disinfection of endoscopes: a counterpoint.

Endoscopes are used widely for the diagnosis and therapy of medical disorders. To prevent spread of nosocomial infection, all endoscopes should undergo thorough cleaning and high-level disinfection following each use. The Food and Drug Administration (FDA) has approved a user-friendly package label for one liquid chemical germicide that requires a 45-minute immersion at 25 degrees C to support a high-level disinfection label claim. Scientific data reviewed here suggest that one can achieve at least an 8-log reduction in M tuberculosis contamination with cleaning (4 logs) followed by chemical disinfection for 20 minutes (4 to 6 logs). The FDA should modify the label to state that if cleaning is accomplished using a standardized cleaning protocol, then a 20-minute immersion at 20 degrees C will be sufficient to achieve high-level disinfection.

FDA Labeling Requirements for Disinfection of Endoscopes: A Counterpoint

Endoscopes are used widely for the diagnosis and therapy of medical disorders. To prevent spread of nosocomial infection, all endoscopes should undergo thorough cleaning and high-level disinfection following each use. The Food and Drug Administration (FDA) has approved a user-friendly package label for one liquid chemical germicide that requires a 45-minute immersion at 25°C to support a high-level disinfection label claim. Scientific data reviewed here suggest that one can achieve at least an 8-log reduction in M tuberculosis contamination with cleaning (4 logs) followed by chemical disinfection for 20 minutes (4 to 6 logs). The FDA should modify the label to state that if cleaning is accomplished using a standardized cleaning protocol, then a 20-minute immersion at 20°C will be sufficient to achieve high-level disinfection.

Liquid disinfecting and sterilizing reprocessors used for flexible endoscopes

In this issue, we evaluate three liquid disinfecting flexible endoscope reprocessors that can be used with a user-supplied liquid chemical germicide (LCG), primarily for high-level disinfection (HLD). Applying most of the same criteria and test methods, we also evaluated a fourth unit, presented separately, that is marketed as a liquid sterilizing reprocessor and must be used with manufacturer-supplied, single-use containers of LCG. Although the sterilizing unit can be used for rigid endoscopes, surgical instruments, and endoscopic accessories, we evaluated its application to the reprocessing of only flexible endoscopes. Our ratings are based on the following: (1) basic performance, such as compatibility with several different types of endoscopes and LCGs, inclusion of all essential reprocessing phases, and exposure of all endoscope surfaces to the LCG and rinse water; (2) safety, such as ensuring that essential reprocessing phases cannot be skipped or omitted, that personnel exposure to LCG vapors is minimized, and that the reprocessor is unlikely to contaminate the endoscope during reprocessing; and (3) human factors design, such as ease of use and installation. We did not perform microbiological testing to confirm HLD or sterilization by any of the evaluated reprocessors because, with a suitably clean endoscope that is in good condition, no evidence indicates that the LCGs used would not be effective on the surfaces that they contact; also, the results would be unique to the two flexible endoscopes that we used for our testing. We rated all four reprocessors Conditionally Acceptable. The units are Acceptable on the condition that users understand that they cannot be used to process the elevator cable channel of side-viewing duodenoscopes; additional conditions apply only to the liquid disinfecting units. However, if the conditions are met, all four units reduce the likelihood of using a contaminated endoscope on a patient and reduce personnel exposure to the LCG. Selection of a unit will be based on the needs and preferences of the individual healthcare facility. Our ratings also assume that these units will be used according to the manufacturers' instructions and the endoscope's operator's manual. Note that, although the evaluated liquid disinfecting units provide detergent-flushing, post-detergent water-rinse, and post-detergent water-rinse-removal phases, manual cleaning of endoscopes before automatic reprocessing is essential, regardless of which reprocessor is used.(ABSTRACT TRUNCATED AT 400 WORDS)

Feasibility of a combined carrier test for disinfectants: studies with a mixture of five types of microorganisms

Background: There is mounting concern regarding the efficacy of many germicides on the market because officially recognized germicidal tests for various classes of microorganisms vary widely and often lack reproducibility and proper quantitation. We report here a carrier method for simultaneously and quantitatively assessing the efficacy of liquid chemical germicides against a mixture of microorganisms of varying degrees of resistance. Methods: In the test, each small glass cup (10 mm wide × 14 mm long) was contaminated with 10 μl of a standardized mixture of Staphylococcus aureus, Mycobacterium bovis bacille Calmette-Guérin, Trichophyton mentagrophytes spores, Sabin poliovirus type 1, and Bacillus stearothermophilus spores in 5% fetal bovine serum. The inoculum was dried for 60 minutes under ambient conditions and covered with 60 μl of the disinfectant under test or a balanced salt solution control for the desired contact time. The carrier was then placed in 2940 μl of an eluent and the eluates assayed separately for the five microorganisms. Tap water was used to dilute the test product as needed. Results: Of the 11 products tested, 2% alkaline glutaraldehyde, 0.6% sodium hypochlorite (about 5000 ppm free chlorine), and a 0.4% quarternary ammonium compound containing 23% hydrochloric acid were effective against all five challenge organisms. A hard-surface spray containing 0.1% o-phenylphenol with 79% ethanol was effective against all but bacterial spores; 70% (volume/volume) ethanol alone and povidone-iodine (1% available iodine) were effective against S. aureus, the mycobacterium, and the fungus; a 3% solution of peroxygen compounds was effective only against S. aureus and the poliovirus; 1.5% chlorhexidine gluconate, 0.06% quaternary ammonia compound, and 0.03% o-phenylphenol + 0.03% p-tertiary amylphenol could inactivate nothing but S. aureus; and 3% hydrogen peroxide was ineffective in all tests. Conclusions: This method shows promise for use with various classes of microorganisms, individually or as mixtures. Its application should enable the classification of germicides according to spectrum of activity.