The Food and Drug Administration never reviewed the procedures needed to clean the complex medical devices that recently infected seven patients with drug-resistant bacteria, killing two of them, an agency official acknowledged on Wednesday.
Now the F.D.A. has asked manufacturers to provide evidence that their recommended disinfection methods work, said Dr. Stephen Ostroff, the agency’s chief scientist.
“Institutions appear to have been doing the recommended procedures, and doing them extremely well,” said Dr. Ostroff, who will become acting commissioner when Dr. Margaret Hamburg departs. But the recent infections, at Ronald Reagan U.C.L.A. Medical Center, show that additional precautions may be needed, he said.
Duodenoscopes have been implicated in similar outbreaks at other hospitals. In 2013, 39 patients at Advocate Lutheran General Hospital in Park Ridge, Ill., were infected with carbapenem-resistant Enterobacteriaceae (CRE), also the cause of the infections in Los Angeles.
In January, officials at Virginia Mason Hospital in Seattle acknowledged that 32 patients had been infected with CRE by duodenoscopes from November 2012 to early 2014. Eleven patients died, but it is not clear that the infections were the cause, as they had other serious medical problems.
The devices are uniquely difficult to disinfect, and there is no expert consensus on the best way to do so now that standard methods have been called into question.
Even when health care providers “appear to be doing everything right, there has been transmission of CRE,” said Dr. Arjun Srinivasan, the associate director for health care associated infection prevention programs at the Centers for Disease Control and Prevention.
Makers of the special scopes defended their disinfection recommendations. John Haberstock, a spokesman for Pentax Medical, said its cleaning protocols achieved a “high level disinfection of duodenoscopes.” Diane Rainey, a spokeswoman for Fujifilm, said the company’s instructions to providers “are appropriate to maintain patient safety.”
A duodenoscope is a long, flexible tube with a tiny camera at the tip. It is typically inserted down the throat of an anesthetized patient to examine the very small ducts that drain the liver or gallbladder.
The inner tubing is intricate and difficult to clean, and can harbor up to 10 billion individual bacteria, said William A. Rutala, an infection control specialist at University of North Carolina Hospitals. By contrast, a surgical forceps may have roughly 100 bacteria on its surface after use in the operating room, he said, and is easily cleaned with heat, detergents and high-pressure sprays.
“When we clean devices for health care, we do it in such a way that even if we don’t clean it perfectly, it’s still clean,” Dr. Srinivasan said. But with the duodenoscope, cleaning must be “perfect every single time.”
In the standard procedure, workers use tiny brushes to clean out the crevices, then hook the duodenoscope to a machine that flushes hard-to-reach inner parts with a disinfecting chemical. The process takes about an hour.
Yet a C.D.C. team investigating the cluster of infections in Illinois found that duodenoscopes remained contaminated with CRE even when there were no recognized lapses in this cleaning process.
The F.D.A. is investigating numerous additional measures, such as sterilizing the devices with toxic gas or sampling them for microbiological cultures periodically.
Ronald Reagan U.C.L.A. Medical Center and Advocate Lutheran General Hospital have begun sterilizing their instruments with a gas called ethylene oxide. Neither has had additional cases of CRE since instituting the procedure.
At the moment, however, the F.D.A. is not willing to recommend ethylene oxide sterilization on a routine basis.
“This agent itself could potentially be quite toxic, not only if not thoroughly aired afterward but in the longer term to people doing the cleaning,” Dr. Ostroff said.
Dr. Srinivasan of the C.D.C. said the toxic residue could be mitigated by letting the duodenoscope sit unused for perhaps 12 hours after it is exposed to the gas. But many hospitals would find such a procedure impractical; duodenoscopes are sometimes needed for emergency procedures.
The C.D.C. is developing a protocol hospitals can use to screen cultures taken from their scopes. At Virginia Mason Hospital, workers clean scopes according to manufacturers’ directions, then test them for potential pathogens and quarantine them for 48 hours until they are confirmed safe.
“Just following the manufacturer’s guidelines was inadequate,” said Dr. Andrew Ross, the hospital’s chief of gastroenterology. The hospital bought 20 additional duodenoscopes to implement the quarantine.
At the University of North Carolina Hospitals, Dr. Rutala is considering a combination approach: cleaning duodenoscopes with manual brushing, then high-level disinfectants, followed by gas sterilization.
He said the number of infections was “very concerning” and called for a swift consensus on new cleaning protocols. At the moment, however, experts cannot say which additional measures should be used by hospitals desperate to prevent further infections.
“None of them are entirely straightforward or potentially easy to implement on a widespread basis,” Dr. Ostroff said. The devices themselves may need to be redesigned, he added.
For now, Dr. Srinivasan said, “there is not a consensus answer.”
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