No perfect method for disinfecting duodenoscopes

Last Updated: 2017-07-26

By Will Boggs MD

NEW YORK (Reuters Health) - Regardless of disinfection and sterilization procedure, cultures of duodenoscopes continue to show bacterial growth in a significant percentage, according to results from the DISINFECTS study.

"The most interesting finding was that when we compared duodenoscopes reprocessed by (three different methods), we found no significant differences between groups for multidrug-resistant organisms (MDRO) or bacterial contamination," said Dr. Mandeep S. Sawhney from Harvard Medical School and Beth Israel Deaconess Medical Center, in Boston.

"Enhanced disinfection methods did not provide additional protection against contamination," he told Reuters Health by email.

Contaminated duodenoscopes have been blamed for recent outbreaks of infections due to carbapenem-resistant Enterobacteriaceae (CRE) and other multidrug-resistant organisms (MDRO).

Dr. Sawhney and colleagues compared the frequency of duodenoscope contamination with MDRO and with any bacterial contamination after reprocessing using three methods of high-level disinfection or sterilization: standard high-level disinfection with orthophthalaldehyde disinfectant (sHLD); standard high-level disinfection with a double cycle of disinfectant exposure (dHLD); and standard high-level disinfection followed by ethylene oxide gas sterilization (HLD/ETO).

After three months the study was closed due to futility, with too few events to evaluate the primary outcome (MDRO contamination), the researchers report in Gastroenterology, online July 12.

At least some bacterial growth (>0 CFU) was detected on 16.1% of duodenoscopes after sHLD, 16.0% after dHLD and 22.5% after HLD/ETO (p=0.21).

Bacterial growth of 10 or more CFUs was detected on 2.3%, 4.1% and 4.2%, respectively.

There were no cases where MDRO were detected.

After adjustment for other variables, there was no significant difference among disinfection methods in the rates of detection of bacterial growth >0 CFU. But detection of bacterial growth of 10 CFU or more was twice as likely after dHLD and 2.4-fold more likely after HLD/ETO, compared with sHLD.

"The most surprising finding was that the HLD/ETO arm in fact appeared inferior to sHLD with regard to our secondary end-point (proportion of duodenoscopes with >=10 CFU growth)," Dr. Sawhney said. "It is highly unlikely that even if we had continued to recruit subjects into the study, this trend would have reversed in the opposite direction to favor the HLD/ETO arm."

"At the Gastroenterology and Urology Devices Panel of the Medical Devices Advisory Committee meeting convened by the (U.S. Food and Drug Administration) in 2015, experts strongly urged the FDA to mandate that all duodenoscopes be sterilized with ethylene oxide," he explained. "The FDA has yet not mandated ethylene oxide sterilization of duodenoscopes. The results of our trial do not support the use of ethylene oxide sterilization in a non-outbreak setting."

Dr. Sawhney added, "We use standard high-level disinfection (sHLD)."

Dr. Raman Muthusamy from David Geffen School of Medicine at the University of California, Los Angeles, who recently reviewed the current practice of duodenoscope reprocessing, told Reuters Health by email, "We still have not identified an optimal way to reprocess duodenoscopes and challenges remain in properly proving a device is 'clean.'"

"Continued attention must be paid to this topic (as it is not entirely resolved) and improved collaboration between industry, regulatory bodies, and healthcare facilities is necessary to achieve significant and rapid advances in endoscope reprocessing," he said.

Dr. Muthusamy said, "I don't have a particular recommended option as each has its limitations and there are practical issues that may limit some of these options. For example, some states don't have ethylene oxide reprocessing facilities while some hospital labs will not perform 'environmental' cultures from equipment or room surfaces, only from specimens obtained from patients."

Dr. Karl K. Kwok, a gastroenterologist at Kaiser Permanente, Los Angeles Medical Center, told Reuters Health by email, "We currently favor a double high-level disinfection as the most practical approach to this challenging clinical problem. As the authors rightly point out, the CDC culturing protocol requires rigorous training and additional personnel and additionally has significant limitations (it is important to note that two major CRE outbreaks in California academic medical centers were traced to culture-negative scopes)."

"Ethylene oxide can damage equipment, and furthermore has been shown to fail in the presence of retained biomaterial," he said. "The liquid chemical sterilant process has certain key requirements for it to function as intended and potentially adds to the complexity of an already complex reprocessing method (i.e., errors of omission or commission)."

"The ultimate solution will likely be multifactorial, including antimicrobial stewardship (judicious use in human and veterinary applications), enhanced methods of reprocessing, and potentially redesign of critical components, to preserve broad access to this lifesaving procedure," Dr. Kwok said.

Dr. Elisabeth Presterl from Medizinische Universitaet Wien, in Vienna, Austria, recently reported microbiologic surveillance results after duodenoscope reprocessing. She told Reuters Health by email, "Our findings underline and demonstrate the efficacy of a bundle of infection-control measures to avoid patient cross-infections resulting from contaminated endoscopes via reprocessing lapses. In our study, we could demonstrate that when following a diligent and validated reprocessing standard, single high-level disinfection is able to provide safe duodenoscope reprocessing."

"There is clearly a need for a diligent and validated reprocessing standard for duodenoscopes," Dr. Presterl said. "A comprehensive post-market surveillance of critical medical devices in general needs to be enforced."

Drs. Muthusamy, Kwok and Presterl were not involved in the study.

SOURCE: http://bit.ly/2uYoZuQ

Gastroenterol 2017.