CRE outbreaks: What should we learn?

Infections with Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria are associated with significant morbidity and mortality and are increasing in incidence globally. KPC- and New Delhi Metallo-beta-lactamase (NDM)- producing bacteria collectively are referred to as carbapenem-resistant Enterobacteriaceae (CRE). They are difficult to detect and treat, and thus are an important issue in hospital infection prevention.

Studies emphasize the importance of early intensification of infection control to interrupt the transmission of KPC-producing Klebsiella pneumoniae, but it is clear that infection control efforts aren't always effective at blocking transmission of the pathogen. A dramatic demonstration of this occurred in 2011 in an outbreak at the US National Institutes of Health Clinical Center. A paper by Snitkin and co-workers describes the process that unfolded in the NIH outbreak and the role that whole-genome sequencing (WGS) of isolates played in understanding how the outbreak progressed despite early implementation of infection control procedures. The study illustrates how WGS can provide evidence for unexpected transmission routes, and concludes that "integration of genomic and epidemiological data can yield actionable insights and facilitate the control of nosocomial transmission."

I think there are additional lessons from this and similar outbreaks, including that it is less than clear how, mechanistically, infection travels from host to host. The NIH staff took every intervention that could be expected to stop the spread, but those failed to break the chain of transmission. There is very limited science behind most infection prevention interventions. We don't understand in a detailed way the trips taken by pathogens as they sojourn from one host to the next, the relative probabilities of survival along the pathways, and other important facets of the contagion process.

These gaps need significant attention -- and funding for both research and education -- if we are to identify the most effective and efficient methods for control and prevention.

(image source: CDC)