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UCLA superbug outbreak: Why the medical scope used is hard to disinfect

Instrument behind superbug outbreak at UCLA can be difficult to disinfect, experts say

The medical device implicated in the superbug outbreak at UCLA's Ronald Reagan Medical Center has a reputation for being tough to disinfect, largely due to its unique design, doctors say.

The device in question -- a duodenoscope -- is used to diagnose and treat problems of the ducts that carry bile and pancreatic fluid, which help the body break down food. It differs markedly from the camera-tipped endoscopes routinely inserted into the colon or esophagus to view polyps or investigate ulcers.

The duodenoscope that apparently spread an antibiotic-resistant strain of enterobacteria has a side-mounted video camera and a small "elevator" designed to steer fine-scale instruments at oblique angles into tiny ducts. 

"There’s a little pocket behind the elevator that’s a potential site for contamination to reside," said Dr. Bret Petersen, a professor of medicine at the Mayo Clinic in Rochester, Minn., who led a 2011 effort by the American Society for Gastrointestinal Endoscopy to establish guidelines for disinfecting the instruments. 

In addition, Petersen said, the last few millimeters of a thin cable connected to the elevator may pose decontamination challenges.

"It’s not purely a design issue from one company so much as it’s probably the generic complexity of the instrument,” Petersen said.

Disinfecting the instrument occurs in stages. The first, called pre-cleaning, involves wiping the instrument with detergents to remove any blood, mucus or solids. Then it is flushed, usually with enzymatic detergents and water, Petersen said. 

Next the instrument goes to a reprocessing area, where it is tested with forced air to detect any potential leaks in the internal channels of the instrument. The duodenoscope is then immersed in water and manually brushed. 

"There’s several different channels, some for air and some for water and some for passing devices through. And they’re all thoroughly brushed," Petersen said.

From there, the vast majority of facilities use an automated machine that subjects the devices to several cycles of liquid germicides. At the end of those cycles is an alcohol flush and forced-air drying, he said.

The automated process can take about 45 minutes, and the devices can be ready for reuse in about two hours, said Dr. Michael Kochman, who heads the American Gastroenterological Assn. Center for GI innovation and technology. 

There are ways to sterilize the devices with a gas called ethylene oxide, but this can be dangerous for technicians because the gas may be carcinogenic, Kochman said.

That's not the only problem. Ethylene oxide may degrade the devices, he said. 

The FDA warned doctors Thursday that the devices could be dangerous for patients because they are so difficult to sterilize. “Meticulously cleaning duodenoscopes prior to high-level disinfection should reduce the risk of transmitting infection, but may not entirely eliminate it,” the warning noted.

Kochman, who teaches at the University of Pennsylvania Health System in Philadelphia, said it may be time to rethink both the design of the device and the way it is cleaned. 

He noted that more than 570,000 of the procedures are performed every year, often leading to timely interventions for serious disease.

"I think it is extraordinarily safe to say that more people have been helped by the procedure and these endoscopes than have been harmed,” he said.

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