The best IPC article of 2018: a blogoff with Brett Mitchell

In honour of Infection Prevention 2018, Brett Mitchell and I are having a blogoff so that you can choose the best IPC article of 2018. This post presents my case, Brett’s post (here) presents his case, and there’s a vote below so that you can choose. The results will be published next Monday morning at Infection Prevention 2018…

So, here’s what I was looking for in the best IPC article of 2018:

  • A key topical issue with findings that challenge and change our practice
  • An intervention study with a clinical outcome
  • Appropriate and high-quality design and methods

The article that has got me thinking more than any other that I have seen in 2018 is this one, by Mathers et al., investigating the role of contaminated wastewater, sinks, and drains in the transmission of CPE. Before this article was published, there was building evidence that contaminated wastewater contributed to CPE transmission. We knew that wastewater was frequently contaminated with CPE, and an elegant experiment showed graphically that there was a theoretical risk of human to human transmission of CPE via contaminated drains. However, the missing piece of the jigsaw was whether CPE contamination of wastewater and drains was a cause of cross-transmission or an innocent bystander. In order to disentangle these possibilities, you need an intervention study.

Intervention studies (as opposed to observational studies) are vital in science, right through from primary school experiments to particle accelerators. You change a variable and observe the impact. If you want to understand whether or not gene X is involved in a biological process, you knockout or modify gene X and observe whether the process stops or changes. (By the way, if Brett happens not to have chosen an intervention study, then I win, by default…!) And it’s the same with CPE contamination of wastewater and drains: the only way to really know whether this is a transmission route for CPE is to do a better job of managing wastewater and drains and observe whether CPE transmission reduces. And this is exactly what the team in the US did. They found that installing hopper covers and sink trap unblockers resulted in a 49% reduction in K. pneumoniae CPE acquisition, and, remarkably, a 71% reduction in K. pneumoniae clinical cultures (more on the details of the study in a previous post, here).

The study isn’t perfect. It’s not one of the gargantuan cluster randomised controlled trials such as the BUGG or BETR-D studies that offer the potential to really put an IPC issue to bed (although, interestingly rarely actually do). In fact, there was no randomisation at all, which is a major methodological limitation. Also, the study design was pre-post without a concurrent control group. This makes it difficult to be sure there weren’t other factors influencing CPE transmission around this time. And there are issues with generalizability too. The study was conducted in an ICU setting, and it’s quite rare to have a hopper (or sluice) in the patient room. This means that the findings won’t be directly transferable to many healthcare settings.

Despite the limitations, I have chosen this article because CPE contamination of wastewater and drains is a hot topic in IPC with important unresolved questions. This is the first study that I’ve seen to provide compelling evidence that CPE contamination of wastewater and drains is an important driver in of CPE transmission and ultimately clinical infection. And these findings will change our day to day IPC practice. The study design is adequate, with an intervention and a strong clinical outcome (although randomisation and a control group would have been even better). Put another way, it’s quite difficult to read this study and not have some sleepless nights thinking about the CPE that may be lurking in your sinks, drains, and hospital wastewater!

And so to the vote…here.

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