A Deadly Duo: MCR-1 Genes and Duodenoscopes


Duodenoscopes are at fault for another infectious disease outbreak, and this time it's with a highly-resistant bacteria.

Medical devices carry an inherent risk for infection control. Invasive applications, frequent use, challenges for disinfection and sterilization, and design flaws are just a few reasons why they are a vulnerable aspect of medical care.

These reusable, flexible medical devices are used to perform procedures like endoscopic retrograde cholangiopancreatography (ERCP) nearly 600,000 times a year. Furthermore, they carry a hefty price-tag of $40,000 a piece, which is likely why, even during outbreaks, hospitals are apprehensive to stop using them and order replacements.

In 2015, a large outbreak of carbapenem-resistant Enterobacteriaceae (CRE) associated with duodenoscope use at the University of California, Los Angeles (UCLA) Medical Center revealed a major issue with the scopes: a design flaw in the most common manufactured brand in use—Olympus—that impacted cleaning and disinfection. The US Centers for Disease Control and Prevention (CDC) and the US Food and Drug Administration (FDA) were forced to provide interim guidance for advanced disinfection practices, and Olympus issued a recall. Still, these findings triggered not only public outcry, but also a political firestorm. Senator Patty Murray initiated investigations to understand the larger scope (pun intended) of the situation. Sen. Murry’s investigation and continued probing revealed ongoing issues with duodenoscopes, particularly those made by Olympus. Of the 25 outbreaks of CRE that were identified, 19 were traced to scopes made by Olympus.

Unfortunately, the problems with duodenoscopes are not over. The results of a recent study and epidemiological investigation at Massachusetts General Hospital revealed the transmission of MCR-1—positive Klebsiella pneumonia between 2 patients likely occurred through the use of a duodenoscope.

Clinicians stumbled across the first case in April 2017 in a patient who had undergone an ERCP procedure, and within a few weeks, a second case was identified. Perhaps most concerning about these cases is that both patients tested positive for K pneumonia with the resistance-conferring MCR-1 gene. The transmission of MCR-1 positive bacteria is extremely concerning as the gene can confer resistance to colistin, an antibiotic of last resort.

MCR-1 genes are deeply worrying and surveillance for these bacteria has been ongoing since they were first identified. As with the transmission of many pathogens, travel plays a large part, and this is why hospitals interview patients on their travel history. In the Mass General case, only the index patient had a relevant travel history, and this is when they could have picked up the resistant bacteria. The only link between the 2 patients was found to be the duodenoscope used for procedures in both patients. Furthermore, genetically, the isolates from both patients were similar, which supported a single source of transmission.

Further investigations and screening tests for MCR-1 in 20 health care workers and 2 household contacts of the patients did not yield any positive results. Assessment of infection control practices for scope reprocessing revealed no failures or breaches in protocol. Swabs from the duodenoscope used grew K pneumonia and Escherichia coli; however, neither carried the MCR-1 gene. Additional investigation into the scope found an intrusion of biomaterial under a sealed distal cap. This finding, as well as an investigation by the manufacturer, Pentax Medical, supported the hypothesis that the device’s flawed design was likely behind the transfer of bacteria.

Frustratingly, the guidance from the FDA and Pentax in January 2017 (prior to the outbreak) encouraged hospitals to inspect the devices and report if there were visible signs of damage, which neither the hospital experts or those at the CDC found in the suspect scope. The challenges in identifying device breakdown leave hospitals at a disadvantage. Pentax Medical went on to recall the scope model in 2018 (after the cases were identified) to replace this problematic part.

Unfortunately, this seems to be a trend—design flaws that go undetected by hospitals and ultimately pose infection control risks. Experts, like those who conducted this study, have urged a move to disposable scopes as it is becoming increasingly clear that the overall design of duodenoscopes inhibits them from truly being disinfected over time. This latest outbreak represents just one of many; however, the transmission of an MCR-1 gene underscores the seriousness of failures in infection control in these devices and the threats to patient safety. The real question is, how much longer will we continue to accept these deadly practices as a norm in health care?

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