A 21st century nosocomial issue with endoscopes
BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2047 (Published 19 March 2014) Cite this as: BMJ 2014;348:g2047
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Having recently undertaken an evaluation of the published evidence for sterile disposable endoscope sheaths in relation to healthcare associated infection and infection control (unpublished), I read Noronha and Brozak’s feature with interest. I commend the authors for highlighting the important problem of cross infection and outbreaks associated with inadequately decontaminated endoscopes and for highlighting some of the alternative approaches available to standard high-level disinfection (which they term ‘liquid reprocessing’), including the use of sheaths.
However, I disagree with Noronha and Brozak’s interpretation of the results of two studies(1;2) they cite which they claim show that use of an endoscope sheath in addition to wiping with alcohol between uses ‘guarantees sterility’. Neither study cited by the authors included assessment of microbiological contamination of endoscopes, and the evidence on which their assertion is based is unclear. Wiping the endoscope with alcohol (intermediate level disinfection), even in combination with the use of a sterile sheath, is not sufficient to render an endoscope sterile, which is usually defined as the absence of all microorganisms including spores.(3)
I am aware of three studies that have assessed endoscopes for microbiological contamination after use following removal of the sheath and intermediate level disinfection.(4-6) While bacteria could not be detected on endoscopes after disinfection in one study(4), bacteria were detected on some endoscopes after disinfection in the other two studies.(5;6) Interestingly, in one of the studies in which bacterial contamination was detected after disinfection, the method of disinfection was considerably more involved than simply wiping with alcohol: immersion in enzymatic detergent after sheath removal; friction rub plus water rinse; disinfection with 70% alcohol-soaked gauze; air drying.(5) Although levels of contamination were found to be low in both studies and unlikely to be clinically significant, the studies demonstrate that use of a sterile disposable sheath and intermediate level disinfection does not ‘guarantee sterility’.
Due to their complex design and heat sensitivity endoscopes cannot easily be sterilised. As such it is recommended that endoscopes undergo cleaning to remove debris and organic matter followed by high-level disinfection(7), which is usually defined as complete elimination of all microorganisms except for small numbers of bacterial spores.(3) Adequate high-level disinfection should eliminate pathogens sufficiently to prevent cross infection(3), and the evidence indicates that it is lapses and breaches in the implementation of the high-level disinfection process, rather than inherent deficiencies in the process, that have been responsible for cross-contamination incidents and outbreaks.(8)
Clearly, it is unacceptable for patients to be infected as a result of an endoscopic procedure, and it is appropriate to consider alternatives to high level disinfection that may be less prone to failure, and may have additional benefits such as decreased instrument turnaround time.
My own assessment of the published evidence on sterile disposable endoscope sheaths led me to conclude that while there is promising evidence that their use, combined with intermediate level disinfection (e.g. wiping with alcohol), may be a safe alternative to high-level endoscope disinfection there are some concerns regarding failures in barrier integrity, and further research is required to convincingly evaluate the risk of infection from sheathed endoscopic procedures versus the risk from standard endoscopy procedures.
Reference List
(1) Lawrentschuk N, Chamberlain M. Sterile disposable sheath system for flexible cystoscopes. Urology 2005 Dec;66(6):1310-3.
(2) Winter SC, Thirwell A, Jervis P. Flexible nasendoscope with a disposable-sheath system versus standard nasendoscopy: a prospective, randomized trial. Clinical Otolaryngology & Allied Sciences 2002 Apr;27(2):81-3.
(3) Rutala WA, Weber DJ, Healthcare Infection Control Practices Advisory Committee. Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008. CDC; 2008.
(4) Alvarado CJ, Anderson AG, Maki DG. Microbiologic assessment of disposable sterile endoscopic sheaths to replace high-level disinfection in reprocessing: a prospective clinical trial with nasopharygoscopes. American Journal of Infection Control 2009 Jun;37(5):408-13.
(5) Elackattu A, Zoccoli M, Spiegel JH, Grundfast KM. A comparison of two methods for preventing cross-contamination when using flexible fiberoptic endoscopes in an otolaryngology clinic: disposable sterile sheaths versus immersion in germicidal liquid. Laryngoscope 2010 Dec;120(12):2410-6.
(6) Jorgensen P, Slotsbjerg T, Westh H, Buitenhuis V, Hermann G. A microbiological evaluation of level of disinfection for flexible cystoscopes protected by disposable endosheaths. BMC Urology 2013;13(1):46.
(7) Department of Health. Choice Framework for local Policy and Procedures (CFPP) 01-06 Decontamination of flexible endoscopes: Operational management. 2013.
(8) Seoane-Vazquez E, Rodriguez-Monguio R, Visaria J, Carlson A. Exogenous endoscopy-related infections, pseudo-infections, and toxic reactions: clinical and economic burden. [Review] [106 refs]. Current Medical Research & Opinion 2006 Oct;22(10):2007-21.
Competing interests: No competing interests
Re: A 21st century nosocomial issue with endoscopes
We appreciate Laura Macdonald’s response to our article on the subject of disposable endoscope sheaths and infection control. Macdonald argues that more studies should be done to determine the safety of using sheaths. Given the current body of evidence, we maintain that use of a sheathed scope achieves the best conditions possible given the pressures of the clinical environment. We disagree with Macdonald’s interpretation that the three studies cited in the response show that sheaths are not sterile. We also disagree with Macdonald’s assertion that endoscope-related outbreaks are primarily caused by failure to adhere to the high-level disinfection (HLD) protocol is the only significant cause of endoscope-related outbreaks. We address these two points because we feel that the response ignores many of the clinical outcomes of using HLD and reflects an attitude that has not served patients well thus far.
Out of three studies cited by Macdonald regarding sterility of sheathed endoscopes, two reported that bacterial contamination on the endoscope shaft after removal of the sheath and intermediate-level disinfection was similar to unsheathed endoscopes after HLD.(1-3) Perhaps Macdonald interprets this as evidence that sheaths do not provide a significant safety advantage over HLD. However, it is important to remember that patients only come into contact with the sheath, not the shaft. The sheath itself is sterile out of the package and simply slides over the endoscope shaft, and has been proven to prevent transmission of pathogens as small as 27 nm.(4) Of course, particles in the immediate environment can get on the sheath during this brief process, but any sterilized instrument is prone to such environmental contamination in a clinical setting. Let this not distract from the fact that a sterilized, impermeable barrier that is easy to install is by far the least prone to failure. The use of the a sheath averts the potential points of contamination in the HLD process, including human error, endoscopic features such as the lumen that may harbor pathogens, and even the HLD materials themselves that may also harbor pathogens. Most importantly, with sheathed endoscopes, the surface that comes in direct contact with a patient’s mucus membrane is discarded after a single use.
As Macdonald points out, these benefits are contingent on how reliable the integrity of the sheath is as a barrier. Thus far, disposable sheaths have an excellent track record. Anecdotally, perforations in single-use disposable barriers have not been reported, after two decades of implementation and over five million uses. In each of three studies cited by Macdonald, in which leak tests were performed on 100 sheaths after endoscopy, leaks or tears were not observed.(1-3)
However, a good track record is not enough. Two published studies from the U.S. Food and Drug Administration (FDA) addressed what might happen in the event of a perforation in the sheath. For each study, authors artificially introduced holes or tears of various sizes in disposable sheaths.(5;6) The first study reported that a small amount of high-titer virus could pass outward from inside the sheath provided there is a significant volume of liquid inside the sheath. The authors comment that either a high concentration of virus or a large volume of liquid is highly unlikely to be present inside the sheath in a clinical setting.(5) The second study tested two sheaths in sequence that had holes or tears in the same spot. After the endoscope was exposed to high-titer virus while covered by the first defective sheath, the sheath was immediately replaced without intermediate-level disinfection. No virus was detected passing outward through the second hole.(6) Since it is highly unlikely that a single sheath will have such perforations, and less likely that two sheaths in a row will have them in the same place, these studies provide convincing evidence that the transmission of viruses (or larger microorganisms, such as bacteria, spores and fungi) is prevented to a very high degree.
Macdonald also asserts that cross-contamination is a result of “lapses and breaches in the implementation of the high-level disinfection process, rather than inherent deficiencies in the process.” We emphatically disagree with the implication that lapses and breaches are the only significant cause of cross-contamination, based on the same article to which Macdonald refers. In the last 15 years of the article’s 30-year meta-analysis (1990-2004), only 48.6% of reports were primarily linked to inadequate decontamination practices according to protocol. The article lists several other factors implicated in the reports, such as equipment malfunction and contaminated HLD materials.(7) In the recent case in Illinois of a drug-resistant strain of E. coli, no lapses in protocol were identified after retrospective review and direct observation.(8)
Arguing that cross-contamination is not caused by inherent deficiencies in HLD reprocessing, Macdonald states that “adequate high-level disinfection should eliminate pathogens sufficiently to prevent cross infection,” but the words “disinfection” and “should” betray the flaws in the assertion. With a contamination rate of 15% in the U.S. using HLD,(9) we question whether it is sufficient to keep blaming only human error.
Nosocomial infections are becoming more severe, as shown in recent endoscope-related outbreaks of drug-resistant bacteria.(8;10) In response, we should take a more thorough approach to preventing infections, rather than relying on incremental improvements to HLD, which have yielded limited results over the years. We believe, use of disposable sheaths is a sensible solution to a long-standing issue in clinical practice that sidesteps the vulnerabilities of HLD and has demonstrated excellent clinical outcomes.
References:
(1) Elackattu A, Zoccoli M, Spiegel J, Grundfast K. A comparison of two methods for preventing cross-contamination when using flexible fiberoptic endoscopes in an otolaryngology clinic: Disposable sterile sheaths versus immersion in germicidal liquid. The Laryngoscope. 2010; 120 (12): 2410--2416.
(2) Alvarado C, Anderson A, Maki D. Microbiologic assessment of disposable sterile endoscopic sheaths to replace high-level disinfection in reprocessing: A prospective clinical trial with nasopharygoscopes.American journal of infection control. 2009; 37 (5): 408--413.
(3) Jorgensen P, Slotsbjerg T, Westh H, Buitenhuis V, Hermann G. A microbiological evaluation of level of disinfection for flexible cystoscopes protected by disposable endosheaths. BMC urology. 2013; 13 (1): 46.
(4) Microtest Laboratories Incorporated Study GLP: Nonclinical microbial barrier test, Slide-on EndoSheaths for ENT scopes. Agawam, Massachusetts, Microtest Laboratories Incorporated, 1998, pp 106–107.
(5) Lytle C, Clavet C, Chaput M, Varney G, To T, Carey R, Baker K. Evaluation of three methodologies for testing disposable ENT endoscope sheaths as viral barriers. Journal of testing and evaluation. 1998; 26 (6): 587--593.
(6) Baker KH, Chaput MP, Clavet CR, Varney GW, To TM, Lytle CD. Evaluation of endoscope sheaths as viral barriers. The Laryngoscope. 1999; 109: 636–639.
(7) Seoane-Vazquez E, Rodriguez-Monguio R, Visaria J, Carlson A. Exogenous endoscopy-related infections, pseudo-infections, and toxic reactions: clinical and economic burden. Current Medical Research and Opinion. 2006; 22 (10): 2007--2021.
(8) Centers for Disease Control and Prevention Notes from the Field: New Delhi Metallo-ß-Lactamase–Producing Escherichia coli Associated with Endoscopic Retrograde Cholangiopancreatography. [Press release] 3rd Jan, 2014 2014.
(9)Bommarito M. A Multi-site Field Study Evaluating the Effectiveness of Manual Cleaning of Flexible Endoscopes with an ATP Detection System [abstract]. In: APIC 2013 Annual Conference; June 9, 2013; Fort Lauderdale. Abstract #040.
(10) Aumeran C, Poincloux L, Souweine B, Robin F, Laurichesse H, Baud O, Bommelaer G, Traore O. Multidrug-resistant Klebsiella pneumoniae outbreak after endoscopic retrograde cholangiopancreatography. Endoscopy. 2010; 42 (11): 895--899.
Competing interests: No competing interests