Manual cleaning and high-level disinfection in an automated endoscope reprocessor (AER) may not reliably prevent transmission of multidrug-resistant bacteria by endoscopes used in endoscopic retrograde cholangiopancreatography (ERCP), according to a field investigation report published in the January 3, 2014, issue of the Morbidity and Mortality Weekly Report.

A cluster of 9 patients infected with New Delhi metalo-β-lactamase (NDM)-producing Escherichia coli led Illinois Department of Public Health and Centers for Disease Control and Prevention (CDC) investigators to the discovery.

The researchers used a case-control study of patients who had been cared for at a single hospital to identify a history of ERCP as a common factor in 6 of 8 cases. They then obtained cultures after manual cleaning and high-level AER disinfection from the ERCP endoscope used in 5 of the case-patients.

"NDM-producing E. coli and [Klebsiella pneumoniae carbapenemase]-producing K. pneumoniae were recovered from the terminal section (the elevator channel) of the device. The E. coli isolate was highly related (>95%) to the outbreak strain by [pulsed-field gel electrophoresis]," the authors write.

46% of Exposed ERCP Patients Were Culture-Positive

The 91 patients who had an ERCP with the culture-positive endoscope were notified of the potential exposure by Advocate Lutheran General Hospital, Park Ridge, Illinois, and asked to return for rectal surveillance cultures. Of the 50 who returned, 46% (23) were positive for NDM-producing E coli.

Melissa Dankel, from the CDC's National Center for Emerging and Zoonotic Infectious Diseases, told Medscape Medical News, "Subsequently, the facility chose to expand their patient notification efforts to include all 243 patients who had exposure to any ERCP endoscope since January 1, 2013."

According to December 27 Daily Herald news report, 105 of 243 patients have responded to letters asking them to come in for screening. The hospital did not respond to a request for comment.

Hospital Had Followed Recommended Steps for ERCP Cleaning

The CDC report notes that the hospital had followed the approved protocol for endoscope reprocessing and that design of the ERCP endoscopes might "pose a particular challenge for cleaning and disinfection." Advocate Lutheran General Hospital subsequently switched from automated high-level disinfection to gas sterilization with ethylene for endoscope reprocessing.

"At this time, CDC recommends facilities reprocess endoscopes as directed by the manufacturer; however, this is a focus of the ongoing assessments. CDC is not recommending a wholesale switch to sterilization; however, facilities should review their endoscope reprocessing practices to ensure all manufacturers' reprocessing recommendations are followed exactly. Any reprocessing recommendations, including sterilization with ethylene oxide (if recommended), would be validated by the manufacturer," Dankel said.

Tip of an Iceberg of ERCP-Transmitted Infectious Organisms?

Infection control specialist Lawrence F. Muscarella, PhD, told Medscape Medical News that the ERCP-associated infection risk identified in the CDC report might be just the tip of the iceberg. Dr. Muscarella said the problem might extend to other infectious agents (and types of gastrointestinal endoscopes) but has gone unrecognized in patients already being treated with antibiotics or with healthy immune systems. "This bacterium's resistance apparently caused a 'perfect storm' to present itself and to reveal the problem," he said.

Dr. Muscarella, who was not involved in the study, has been studying factors affecting infection risk associated with problems in endoscope reprocessing. He said standard endoscope-reprocessing guidelines are effective provided the disinfectant contacts all of the instrument's surfaces, but endoscope design might require more scrutiny and possibly modification to make that possible.

Endoscope Structure Might Prevent Disinfection

"The ERCP endoscope's elevator wire channel is 'sealed' in some newer models to prevent its contamination with such bacteria and superbugs as carbapenem-resistant Enterobacteriaceae, or CRE. Though it might have been, I am not convinced that this design change was adequately controlled, which could bring the [US Food and Drug Administration's (FDA's)] regulation of medical devices into focus. It may be that the 'sealed' elevator wire channel, or the 'sealed' distal hood or case at the ERCP endoscope's distal tip, is retaining debris and infectious CRE (inaccessible to the disinfectant and cleaning brush) that are being transmitted to patients during ERCP. Definitive testing of this possibility would require opening up this channel and also removing this hood and sampling them, which would admittedly and unavoidably destroy the endoscope," Dr. Muscarella said.

Dr. Muscarella recommended that (at least until the more precise causes of these CRE outbreaks are identified) the ERCP's elevator wire channel, if exposed, be manually reprocessed, not reprocessed using an AER unless the AER's manufacturer provides the hospital with written verification that its AER model has been both validated and cleared by the FDA, through the 510(k) process, for reprocessing all of the specific model numbers and types of ERCP endoscopes in the medical facility's inventory.

"If an outbreak is detected, consider dismantling the ERCP endoscope and microbiologically sampling all of its internal surfaces, including the sealed elevator wire channel and distal hood to rule either out as, or to confirm either to be, a source of the outbreak's strain of bacteria," Dr. Muscarella said. If the sealed distal hood is removed, cultured, and found to harbor CRE, Dr. Muscarella suggests manufacturers might redesign the hood as a disposable component to be removed during reprocessing to ensure that this area, where the forceps is housed, comes into direct contact with the disinfectant.

Dr. Muscarella emphasized that bacterial resistance to antibiotics does not necessarily translate to a resistance to a high-level disinfectant.

"This is an important point. In general, high-level disinfectants rapidly kill vegetative bacteria, such as CRE, provided the disinfectant is not precluded from contacting the organism by the reusable instrument's physical design," he said.

The authors and Dankel have disclosed no relevant financial relationships. Dr. Muscarella is president of LFM Healthcare Solutions, LLC, a consulting firm that provides infection control audits and analysis to healthcare facilities.

Morb Mortal Wkly Rep. 2014;62:1051. Full text