A few years ago, researchers from 3M Co. tested 245 endoscopes - long tubes used to look inside the colon and other organs - to see whether the devices had been properly scrubbed of blood, tissue, and other human debris.

The results of the tests, conducted at five U.S. hospitals, were not what anyone would want to hear before going in for an exam.

The scientists gave a failing grade to 10 out of 30 complex devices called duodenoscopes, which have been in the spotlight this year after federal officials linked them to multiple outbreaks of dangerous, drug-resistant infections.

The 3M researchers also detected evidence of debris inside other more commonly used kinds of endoscopes. In a 2013 issue of the American Journal of Infection Control, the scientists reported that 24 percent of gastroscopes and 3 percent of colonoscopes had not been adequately cleaned.

In practice, those scopes would then have been given a liquid germicide bath intended to kill bacteria harbored by the lingering debris.

But infection-control experts say breakdowns at any point in the "reprocessing" of scopes - cleaning, disinfecting, and thorough drying - are cause for concern, especially with the increasing emergence of bacteria that can survive treatment with antibiotics.

Reprocessing endoscopes is a tedious, multistep task performed by workers making as little as $13 an hour who are required to be certified by just two states, New Jersey and New York. The devices are far too expensive to use just once - duodenoscopes can run $40,000 - so the only option is cleaning with relentless attention to detail.

"You can't cut a corner," said Joseph Charleman, chair of the surgical processing program at Berkeley College, a career-training school with nine locations in those two states.

The how-to manual for cleaning and disinfecting one duodenoscope made by Olympus, with U.S. headquarters in Center Valley, Pa., runs 106 pages. In March, the company issued a 10-page supplement after scrutiny from the Food and Drug Administration.

Aside from the difficulty of the task, there is a more basic reason scopes are not always cleaned thoroughly. Hospitals often are not checking the work, said Michelle J. Alfa, a clinical microbiologist at St. Boniface Research Centre in Winnipeg, Manitoba.

"Most of the health-care facilities in the U.S. and Canada don't actually monitor how well the cleaning is done by the staff," said Alfa, who validated the testing method used in the 3M study. "They don't really know."

Physicians warn that any concerns about the cleanliness of endoscopes must be balanced against patients' need for the slender, life-saving devices, which feature miniature cameras and narrow channels through which tools can be inserted to take tissue samples from deep inside the body.

Duodenoscopes are used 500,000 times a year to examine and drain fluids from the pancreatic and bile ducts, including in patients who are gravely ill with cancer. There is no other way to get the job done short of cutting open the patient, which would be far riskier.

Gastroscopes are used to diagnose such problems as internal bleeding and tumors, and colonoscopes are familiar to anyone age 50 and up as a prime screening tool in the prevention of colon cancer.

Professional medical societies caution that the rate of infection transmission from endoscopes is very low, as reported by hospitals.

Even for duodenoscopes, which have been linked to outbreaks of deadly, drug-resistant "superbugs" in Seattle, Los Angeles, and the Chicago suburb of Park Ridge, Ill., the total number of reported infections is well under 1 percent of those treated with the devices.

But that low figure is misleading, says biomedical engineer Lawrence Muscarella, a Montgomeryville infection-control consultant.

That's because bacteria can be transmitted to a patient and merely become "colonized" - taking up residence in the body - without immediately causing a problem, he said.

An infection could take hold weeks or even months later. For instance, a patient might have a scope procedure that seems to go well. Months later, that patient goes in for unrelated surgery and is given a course of antibiotics. If the medication wipes out the patient's native intestinal bacteria, that creates an opportunity for those old colonized microbes to flourish, creating a potentially devastating, drug-resistant infection.

Bottom line: By the time many infections manifest themselves, health-care providers and their patients have no idea they were transmitted by the scope, Muscarella said.

"How many are we not capturing?" he asked.

Even when hospitals go looking for problems, they cannot necessarily make the case linking scopes to infection.

In March, Thomas Jefferson University Hospital said that from January 2013 to June 1, 2014, it had identified eight patients treated with duodenoscopes who also became infected with bacteria resistant to potent antibiotics called carbapenems. Two patients died.

But after an investigation that involved laboratory testing, hospital officials said they found no proof the scopes were to blame.

There was no trace of the superbugs on any of the scopes in question, hospital officials said. However, the devices had been reprocessed multiple times since being used on the patients who developed infections, so any such trace likely would have been removed.

Historically, most infectious outbreaks tied to dirty endoscopes have been attributed to a failure to follow some part of the cleaning and disinfection procedure.

Berkeley College's Charleman says a properly trained technician may need two hours per scope to follow all the steps to ensure it is ready for reuse, though times may vary if the hospital uses automated washers for any part of the process.

Charleman said he knew of occasions when rushed technicians have left dirty scopes in a sink overnight, or have used less than the recommended amount of germicide in order to save money or because they ran out of chemicals.

In other cases, technicians report pressure from physicians to get the scopes ready for use more quickly, he said.

"I'm $13 an hour, and I've got the surgeon who built the hospital screaming at me," he said. "What am I going to do?"

"People will skip steps," said Kofi Poku, an instructor at Berkeley.

One solution is certification, as required by New Jersey law, Charleman said.

Pennsylvania State Rep. Mauree Gingrich (R., Lebanon) has sponsored a bill requiring surgical-processing technicians to be certified. But the measure was opposed by the Hospital and Healthsystem Association of Pennsylvania.

A spokeswoman for the association said the group had not considered whether the measure would force hospitals to pay workers more. Rather, she said, the group sought only to "preserve workforce flexibility."

In practice, prominent area hospitals tend to hire certified techs even though not required by law.

But certification and training are not guarantees. This year, the FDA said that even when guidelines were followed to the letter, the complex internal mechanisms in duodenoscopes can still harbor bacteria.

The agency is working with manufacturers Olympus, Fujifilm, and Pentax Medical on other possible solutions.

Meanwhile, the best that hospitals and workers can do is maintain constant vigilance and recognize that these complex devices can't be rushed back into service, Charleman said.

"It's tedious, but attention to detail needs to be maintained," he said.

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@TomAvril1