Duodenoscopes had similar rates of contamination after double high-level disinfection, standard high-level disinfection, or standard high-level disinfection followed by ethylene oxide gas sterilization, a randomized, prospective study of 516 bacterial cultures of 18 duodenoscopes showed.
“Our results do not support the routine use of double high-level disinfection or ethylene oxide sterilization for duodenoscope reprocessing,” wrote Graham M. Snyder, MD , of Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, and his associates. They stopped the study after 3 months because none of the duodenoscopes cultured multidrug-resistant organisms, the primary endpoint. “[We] found that in the nonoutbreak setting, duodenoscope contamination by multidrug-resistant organisms is extremely uncommon,” they wrote in the October issue of Gastroenterology (doi: 10.1053/j.gastro.2017.06.052). However, 16% of duodenoscopes cultured at least one colony-forming unit (CFU) after either standard high-level or double high-level disinfection, and 23% of duodenoscopes produced at least one CFU despite standard high-level disinfection followed by ethylene gas sterilization (P = .2), the investigators reported.
Outbreaks of carbapenem-resistant Enterobacteriaceae infections have been traced to duodenoscopes, even though they were reprocessed according to manufacturer instructions. In 2015, the Food and Drug Administration responded by warning that the design of duodenoscopes might preclude effective cleaning. Reasons for residual contamination remain uncertain, but biofilms, which are notoriously resistant to standard disinfection methods, might be a culprit, Dr. Snyder and his associates noted. Accordingly, some experts have suggested repeating the reprocessing cycle or adding ethylene oxide sterilization, but these measures are costly, time intensive, and not widely available. Furthermore, their efficacy “has never been systematically studied in a nonoutbreak setting,” the researchers wrote.
In response, they studied 516 cultures of elevator mechanisms and working channels from 18 reprocessed duodenoscopes (Olympus, model TJF-Q180). Immediately after use, each duodenoscope was manually wiped with enzymatic solution (EmPower), and then was manually reprocessed within an hour before undergoing automated reprocessing (System 83 Plus 9) with ortho-phthalaldehyde disinfectant (MetriCide OPA Plus) followed by ethanol flush. One-third of the duodenoscopes were randomly assigned to undergo double high-level disinfection with two automated reprocessing cycles, and another third underwent standard high-level disinfection followed by ethylene oxide gas sterilization (Steri-Vac sterilizer/aerator). All instruments were stored by hanging them vertically in an unventilated cabinet.
Multidrug-resistant organisms were cultured from 3% of rectal swabs and duodenal aspirates, but not from any of the cultures of duodenoscopes. Therefore, the study was stopped for futility. The enhanced disinfection methods failed to prevent contamination, compared with standard high-level disinfection, the researchers noted. Ten or more CFUs grew in 2% of duodenoscopes that underwent standard high-level disinfection, 4% of those that underwent double high-level disinfection, and 4% of those that underwent high-level disinfection followed by ethylene oxide sterilization (P = .4).
“There is no consensus on what parts of the standard high-level disinfection process should be repeated,” the investigators wrote. “It is uncertain if the addition of a second cycle of manual reprocessing might have improved the effectiveness of double high-level disinfection.”
Funders included the American Society for Gastrointestinal Endoscopy and Beth Israel Deaconess Medical Center. The investigators reported having no conflicts of interest.