CDC: Superbug NDM-1 Spreads Within a US Hospital

Last night, prompted by Michael Coston’s excellent primer on NDM-1 (one of a set of short courses he publishes periodically), I scrolled through the literature to see what had happened recently with the spread of the “Indian superbug” — actually a gene and enzyme that were first spotted in 2008 and create resistance to almost all antibiotics. (My past posts on NDM-1, going back several years, are here.)

There was a lot to see: Cases in countries as varied as Belgium, Japan, Oman, Singapore and China. Indications that transmission of NDM-1, which at first indicated some travel or family connection to South Asia, has become a pan-European problem with clusters in several countries. Concern that international travelers are transporting bacteria containing the gene without realizing it. And, disappointingly, reassurances from within India, in a new study, that it can “easily combat” NDM-1 — though the fact that a study was conducted, as opposed to the problem just being denied out of existence, must be an encouraging sign.

That tour through the literature made me curious what has been happening in the United States since NDM-1 was first identified in patients here two years ago this week, and I made a note to check when I got back to work today. And then the Centers for Disease Control and Prevention forestalled me, by announcing this morning that there have been 13 cases in the United States so far — including two in which the infection apparently spread within the same hospital.

Here’s the new news, via the CDC’s Morbidity and Mortality Weekly Report, or MMWR:

A woman who lives in Rhode Island but was born in Cambodia went back to Southeast Asia to visit in May 2011. She was still there in December 2011 when she was diagnosed with spinal cord compression and hospitalized in Ho Chi Minh City. She came back to the United States in January, was immediately hospitalized again, and was diagnosed with lymphoma and started in-patient chemotherapy. By February, she was exhibiting signs that she was carrying highly resistant bacteria in her bladder — important, because for most of her hospitalizations, she had been catheterized, which means that healthcare personnel were much more exposed to her urine than if she were using a toilet or even a bedpan.

In early March, a sample of Klebsiella pneumoniae from her urine, sent by the Rhode Island hospital to the CDC, was found to contain NDM-1. The woman was discharged March 26. On March 30, one of the seven patients who were on the hematology/oncology unit at the same time was discovered to be carrying NDM-1 as well. CDC analysis confirmed it to be the same strain.

So: This was probably predictable. It is also very much not good. Here’s why: First, NDM-1 is extremely drug-resistant; out of the whole vast armament of antibiotics, it responds in most cases only to an old and toxic drug called colistin and a new and sometimes less-effective one called tigecycline. Second, it resides on a snippet of DNA that has been shown to hopscotch easily among bacterial species, including nearly ubiquitous E. coli. And third, the bacterial species in which NDM-1 has been identified tend to be ones that are especially good at surviving on hard surfaces in hospital rooms — bed rails, IV poles, computer touchpads — and take aggressive, attentive cleaning to remove.

The CDC’s report today does not conclude how the NDM-1-containing bacteria got transferred to the second patient. It does note that the two patients were cared for by different physicians and nurse practitioners, and did not stay in the same room either at the same time or subsequently. It also observes that the first patient was allowed to stroll the floor and chat while she she was under suspicion of harboring another serious resistance factor, KPC, and was not put into isolation until the NDM-1 was confirmed — and that she had “at least one” episode of incontinence while outside her room. (It also notes that, after transmission was detected, 23 members of the nursing staff who cared for both patients were asked to volunteer for tests to see if they were carrying NDM-1, and only one complied.)

I’ll let my infection-control readers — come on, I know you’re out there — judge from your professional standards whether the hospital did anything wrong in allowing the patient to leave her room or in not insisting that all its staff be tested afterward. I’d love to hear your comments.

I do think though that this cases raises several interesting questions. The first is travel history: At this point, must anyone with medical history in South or Southeast Asia  be considered an infection risk? The second is patient control: On what evidence do you put patients into isolation and confine them to their rooms, and should it be sooner than is done now?

Final question: These grave antibiotic-resistance factors are continuing to come across US borders (when they don’t arise here to start with). If we can’t detect and stop them, then hospitals are going to have to be more reliably rigorous in containing them. Any hospital will tell you that they already take infection prevention seriously. What else will they have to do — and how much more will it cost?

Cite: Carbapenem-Resistant Enterobacteriaceae Containing New Delhi Metallo-Beta-Lactamase in Two Patients — Rhode Island, March 2012. Morbidity and Mortality Weekly Report (MMWR). June 22, 2012 / 61(24);446-448



Leave a Reply

Your email address will not be published. Required fields are marked *