SYSTEM 1E® Liquid Chemical Sterilant Processing System as an Effective Sterilization Method for Duodenoscopes


An article in the MONTH 2016 issue of the American Journal of Infection Control discusses the efficacy of SYSTEM 1E® Liquid Chemical Sterilant Processing System (SYSTEM 1E®), which was tested on duodenoscopes of various designs under worst-case processing conditions. 

The following is a summary of the data presented in this article. A full reference for the original article, from which all information below is gathered, can be found at the conclusion of this post.


In recent years, a significant number of infection outbreaks, some involving highly resistant organisms, have been traced to reusable, high-level disinfected duodenoscopes, irrespective of manufacturer or model. As these outbreaks cannot be traced to lapses in duodenoscope cleaning or reprocessing, there is an ongoing effort to investigate these transmission events that have resulted in adverse patient outcomes.

At the FDA Gastroenterology-Urology Devices Advisory Panel Meeting in May 2015, the panel majority advocated for an escalation from high-level disinfection to sterilization as the new reprocessing standard for duodenoscopes, in line with the re-classification of duodenoscopes as critical medical devices as opposed to semicritical devices. Since current duodenoscope designs cannot withstand high-temperature sterilization modalities, two low-temperature processes were discussed: ethylene oxide (EO) and liquid chemical sterilization.

For most liquid chemical sterilants, the prolonged exposure time needed to achieve sterilization is the rate-limiting factor. Currently, SYSTEM 1E® is the only FDA-approved liquid sterilant method able to achieve sterilization within a 23-minute validated cycle. SYSTEM 1E® is also the only method in the U.S. cleared for sterilization of reusable, cleaned, critical medical devices. In accordance with recent FDA recommendations for reprocessing system manufacturers to perform additional testing on their systems, STERIS tested their SYSTEM 1E®, which makes use of peracetic acid-based chemistry, under worst-case conditions.


Duodenoscopes from two major manufacturers (Olympus and Pentax), with both open and closed elevator guide wire designs, were tested under extreme spore-loading conditions. For each of three test cycles on three representative duodenoscope models, the device was cleaned, and all channels were then inoculated with a high spore burden of Geobacillus stearothermophilus (10 times the standard spore burden used for testing). Following inoculation, the device was dried for greater than 60 minutes.

The System 1E® processing cycle was then performed under worst-case conditions, including the use of end-of-shelf-life peracetic acid, lower-than-normal pump output flow rate, and the lowest acceptable UV intensity. In addition, the sterilization cycle was abbreviated to 2.5 minutes of exposure time, less than half the length of a complete 6-minute cycle. Following processing, each test device was harvested using sodium thiosulfate. Harvested samples were then filtered, plated onto tryptic soy agar, and incubated for seven days.


All inoculated areas of all duodenoscopes tested under extreme conditions were shown to have greater than a 6 log10 reduction in spore load, at an exposure time that is less than half of the standard length of SYSTEM 1E®’s liquid chemical sterilization cycle. Both positive and negative test controls met acceptance criteria.


After rigorous FDA-requested testing, System 1E® has been shown to be an effective, safe, expeditious, and convenient liquid chemical sterilization method for duodenoscopes. System 1E® achieves sterilization of duodenoscopes of distinct designs, even under the harshest of conditions. System 1E® should replace high-level disinfection as the premier duodenoscope reprocessing technique.


McDonnell, G. et al. 2016. Effectiveness of the SYSTEM 1E Liquid Chemical Sterilant Processing System for reprocessing duodenoscopes. American Journal of Infection Control. DOI: