Guest Post by Maryn McKenna
The UCLA Health System announced earlier this week that seven patients—two of whom died—became infected by highly drug-resistant bacteria that remained on pieces of medical equipment after disinfection, and 179 more were exposed to the bacteria and are at risk of developing infections.
The outbreak is one of several that have occurred in the United States in connection with duodenoscopes, complex flexible tubes that are used to treat problems in narrow ducts in the liver and pancreas. In each outbreak, despite the devices being cleaned, patients have been infected with superbugs known as CRE, short for carbapenem-resistant Enterobacteriaceae: a group of bacteria that reside benignly in the gut but have acquired an array of genetic defenses against antibiotics, including to the last-resort drugs carbapenems. CREs remain vulnerable to only one or two antibiotics, and CRE infections can kill two in five patients.
On Thursday, the Food and Drug Administration issued a warning about the difficulty of cleaning the devices, which it said are used at least 500,000 times per year in the US. The agency said it has been notified of 135 patient infected with CRE by duodenoscopes since January 2013 and added, “It is possible not all cases have been reported.”
The UCLA episode follows a large outbreak at a Seattle hospital and a separate one in Illinois along with smaller ones in other states. It is causing alarm because the superbugs transmitted by the scopes are a growing problem in the US, and because there can be such a long lag time—weeks or months—between when patients are exposed and when they develop symptoms of infection.
For a better understanding of the problem, I talked to Dr. Alexander J. Kallen, a medical epidemiologist in the division of the Centers for Disease Control and Prevention that handles infections transmitted in healthcare.
Maryn McKenna: Are all these outbreaks similar?
Alexander Kallen: They’re related in that they all involve a small number of scopes—duodenoscopes, which are specialized endoscopes—with persistent contamination, which ended up in each case with 100 to 200 people exposed. Most people did not develop infections; they ended up colonized with the bacteria, but that is still a problem from a community standpoint (because they may be able to pass the bacteria along).
MM: Is there any other relationship among them?
AK: All three large outbreaks that we’re aware of, while they were CRE, were all different types of CRE—and all types that are unusual in the United States. In Illinois, which we at the CDC investigated, it was a type called NDM, in Los Angeles it is a type known as OXA, and in Seattle it was a type known as Amp-C. These are very unusual organisms, so to have a cluster of them definitely prompts an investigation. And they may turn out to be a canary in the coal mine for the difficulty of cleaning these scopes. If what had been passed between these patients because of the scopes was regular old E. coli, we would never have noticed, because it is not an unusual bug.
MM: Do you have any sense of where the infections originated?
AK: They were likely imported originally by people who got healthcare outside the United States. But we looked hard in Illinois for instance to try to identify the original person and were not able to.
MM: Surely this isn’t the first time there have been outbreaks of illness, even of resistant bacteria, from endoscopes?
AK: No. But the outbreak we investigated in Illinois in 2013, which we reported in the Journal of the American Medical Association, is the first time that we know of where there was transmission of a highly resistant pathogen, from a scope, unrelated to an infection-control breach. You almost always see that someone forgot this step or that step. But in these last three outbreaks, there was persistent contamination despite not identifying a breach, and that is fundamentally different. It starts to raise the suspicion this is more a fundamental issue with these types of scopes, rather than just failures to adhere to recommendations for cleaning.
MM: These scopes are obviously complicated. It is possible that they just can’t be sterilized?
AK: Technically they’re not sterilized, because they aren’t intended for use in sterile spaces in the body the way surgical instruments are. They undergo high-level disinfection, a step below sterilization. All these devices are required to have instructions for cleaning that are validated by the FDA, but it is possible that what is validated via tests in a lab under certain circumstances is one thing, and performing the steps in practice is something different. That may also be true for a scope that is brand new versus one that has been used for a year or two, that it acquires persistent contamination that once established can be very difficult to eradicate. In our investigation in Illinois, the scope that was sent to us had been out of use for weeks or months and we were still able to recover bacteria from it.
MM: At the CDC, you’ve been watching the CRE problem build for 15 years. What do these outbreaks mean for that larger epidemic?
AK: It’s important to say that the spread from duodenoscopes is a tiny portion of the CRE problem. But it highlights that the central issue with CRE is person to person spread between people in medical facilities. The people who are at risk, and who get CRE, tend to be people who have complex medical problems and spend a lot of time in hospitals, nursing homes, long-term acute care facilities. In the Illinois investigation, people were infected in the hospital and then were sent out to long-term care and transmitted CRE to their roommates.
MM: Do you see any hope for controlling further spread?
AK: CRE is still rare in most places in the US, but we have not previously been able to identify outbreaks early enough to intervene. There is a movement in the CDC and in some parts of healthcare to change the approach to preventing the transmission of multi-drug resistant organisms by collecting very granular data and sharing it regionally among institutions. I personally think that has a great chance of success.
Maryn McKenna blogs for National Geographic’s the Plate and is writing a book about antibiotic use in agriculture for National Geographic Books.