Five Percent of D.C.’s Enterobacterial Isolates Are CRE?

I’ve discussed before how difficult it is to measure the frequency of CRE (carbapenem-resistant enterobacteriaceae–E. coli and relatives that are usually resistant to all treatment, with the possible exception of colistin). This is, in part, due to a ‘denominator problem’: many clinical isolates aren’t included in the calculation, leading to possible overestimates of the frequency of CRE. With that as prelude, we bring you this story about a D.C. initiative to measure CRE at the city’s hospitals (boldface mine):

That was the finding of a citywide study completed over 15 weeks examining the prevalence of the multidrug-resistant bacteria called carbapenem-resistant Enterobacteriaceae, or CRE. Of about 1,000 patients who were tested across the District, there was a 5.1 percent prevalence rate of CRE, according to results released by the D.C. Hospital Association….

The study — which included Children’s National Medical Center, George Washington University Hospital, MedStar Georgetown University Hospital and MedStar Washington Hospital Center, among others — was conducted in response to growing global concerns about the threat of antibiotic resistance, officials said.

CRE is particularly alarming because it is easily transmissible, is often resistant to the antibiotics of last resort and has a particularly high mortality rate. To date, there has not been a significant CRE problem reported in the District, although the National Institutes of Health Clinical Center in Bethesda battled a deadly CRE outbreak in 2011.

Across the District, the CRE study found acute care hospitals had a slightly lower prevalence of CRE among patients compared with sub-acute care facilities, at 4.8 percent and 5.7 percent, respectively.

The hospital association declined to release hospital-specific data to the public, saying individual facilities have been alerted to their prevalence rates. Nelson said none of the facilities represented great outliers in their prevalence rates.

Dr. Roberta DeBiasi, division chief of infectious disease at Children’s National Health System, said she was not surprised by the results of the study…

The hospitals used DNA testing technology from Gaithersburg-based OpGen Inc. (NASDAQ: OPGN) to more quickly identify bacteria that were multidrug-resistant — or had genes that could potentially lead them to become resistant, officials said.

The rapid testing allowed hospitals to identify patients who were colonized with multidrug-resistant bacteria. That means they have not been sickened by it, or are silent carriers, DeBiasi said. Those patients are of particular concern because they can create the possibility of unidentified transmission between patients.

While it’s incredibly difficult to tell what was actually observed–and this study, to the best of my knowledge, has not been publicly released–a five percent colonization rate of CRE seems incredibly high. Keep in mind the sub-acute care facilities (long-term hospital treatment) didn’t have much higher rates of carriage. Either there’s something really weird with the sampling design (or detection method), or else we have a real problem that’s about to explode. I can’t see how a five percent CRE carriage rate in asymptomatic people–again, I can’t tell if that’s an accurate statement–will, probably sooner rather than later, result in a five percent CRE infection rate. And that’s a real crisis.

The findings of this study need to be made public so experts can understand this better. Despite the reporter’s best efforts, it’s really hard to understand what the study found.

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