Preventing Future Endoscope-Associated CRE Outbreaks

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Dr. William Rutala and Dr. David Weber, two very prominent and respected researchers and authors in the fields of Infection Control and Hospital Epidemiology, wrote this commentary in order to shed light on controversies that have arisen in the past year surrounding the reprocessing of flexible duodenoscopes.

 

The commentary discusses three major topics:

  1. an outbreak of carbapenem-resistant Enterobacteriaceae (CRE) traced to duodenoscopes in a medical center during the period November 2012 – August 2013 that was the subject of an article by Wendorf et al.1
  2. currently available alternatives that might improve the safety margin associated with reprocessing duodenoscopes
  3. how to prevent future outbreaks associated with duodenoscopes and other gastrointestinal (GI) endoscopes

 

Medical Center CRE Outbreak:

A novel strain of E. coli was identified among patients who had undergone endoscopic retrograde cholangiopancreatography (ERCP).  This same E. coli strain was also isolated from two of eight duodenoscopes in use at the medical center.  What is important to note is that upon reviewing the duodenoscope reprocessing procedures being performed at the medical center at the time of the outbreak, no breaches in reprocessing protocol could be identified.  Also noteworthy is the fact that the association between duodenoscopes and the novel E. coli strain established through investigation of this outbreak became apparent as a consequence of the fact that the E. coli strain was drug-resistant.

 

Duodenoscopes have long been recognized as being very complex in design.  They are also considered to be more complicated in design than other GI endoscopes, because they are equipped with a distal tip elevator mechanism.  The elevator mechanism is designed to deflect the angle of diagnostic and therapeutic accessories that exit the suction/instrument channel so that they can reach the anatomical structures being examined and remain visible in the field of view of the side-viewing duodenoscope optics.

 

The key question that has arisen as a consequence of the CRE outbreak referenced in the commentary, as well as other similar duodenoscope-related outbreaks that have been identified, is whether current reprocessing guidelines are adequate to insure that reprocessing yields an endoscope that is free of microbial pathogens.

 

Increasing the Duodenoscope Reprocessing Margin of Safety – Currently Available Alternatives:

The authors state that the margin of safety associated with reprocessing endoscopes is minimal to nonexistent.  The reason for this lack of a safety margin is that when comparing the initial level of microbial contamination on an endoscope at the conclusion of a patient procedure to the quantity of microbial contamination that is either removed or eradicated by the cleaning and high level disinfection (HLD) steps of the endoscope reprocessing protocol, those quantities are approximately equal.  Therefore, any decrease in the efficacy of either cleaning or HLD can result in the retention of viable microbial growth on a reprocessed endoscope.  This is unlike the cleaning and steam sterilization of surgical instruments, in which the margin of safety far exceeds (by several orders of magnitude) the expected microbial load that is initially present on the instruments after a patient procedure.

 

Therefore, what can be done to increase the margin of safety associated with reprocessing endoscopes?  The authors state that there is no single, simple, and proven technology, nor is there a prevention strategy that hospitals can use to guarantee patient safety.  However, the following suggestions are proposed:

  1. Emphasize the enforcement of evidence-based practices such as equipment maintenance and routine audits of reprocessing staff with at least annual competency testing.
  2. Thoroughly train reprocessing staff on duodenoscope reprocessing protocol, including new recommendations for brushing and fluid flushing activities.
  3. Strictly adhere to current endoscope reprocessing guidelines.
  4. Consider periodic microbiologic surveillance of duodenoscopes to assess microbial contamination, but understand that many important questions remain unanswered regarding how to conduct the surveillance and how to interpret and act upon data that supports the presence of endoscope contamination after reprocessing.

 

A comprehensive table is included in the commentary that summarizes the advantages and disadvantages of various HLD and sterilization methods that might be considered as enhancements to incorporate into the endoscope reprocessing protocol over and above routine cleaning and HLD of GI endoscopes.

 

Preventing Future Endoscope-Associated Outbreaks:

The commentary concludes with the following four suggestions as to how future endoscope-associated outbreaks might be prevented were presented in a detailed table:

  1. Overcome challenges that GI endoscope design poses to HLD.
  2. Rigorously adhere to current endoscope cleaning and disinfection standards.
  3. Implement enhanced duodenoscope reprocessing methods (e.g., ethylene oxide sterilization with periodic microbiologic surveillance, double HLD with periodic microbiologic surveillance).
  4. Explore future methods to prevent GI endoscope-related outbreaks (e.g., steam sterilizable GI endoscopes, disposable sterile GI endoscopes, capsule endoscopy, blood tests, and stool tests).