Dispersal of CPE from contaminated sinks and drains: a refection from Infection Prevention 2019

I’ve spent the last couple of days up in Liverpool for Infection Prevention 2019. One of the highlights was a talk by Dr Paz Aranega-Bou on the issues around contamination of sinks and drains. Paz flagged a paper just published in JHI investigating the dispersal of CPE in a sink/drain test risk at PHE, showing the CPE can make its way from contaminated drains to sink and surrounding surfaces via splashback.

Figure 1: PHE’s model test rig for sink and drain contamination in hospitals

The issues related to Gram-negative (and especially CPE) contamination of sinks and drains have created a bit of a back-catalogue on this blog. I think it’s fair to say that this is a clear problem without an obvious solution. We have many gaps in our understanding around CPE contamination of sinks and drains, and the model hospital sink/drain rig at PHE provides a system for filling some of these knowledge gaps. The study used settle plates to illustrate splash-related journey of CPE out of the sink (in splash-forming units, sfu!). One of the major factors associated with higher levels of dispersal was slow drainage. Dispersed CPE was even detected from optimally designed hand hygiene sinks, with the drainage inlet at the back (albeit at a lower level than from sinks with drain inlets underneath the faucet.

Now, for anybody who works in a ward, you’ll know that slow drainage is a frequent problem due, in part, to old plumbing in many parts of the NHS, but also due to the exotic variety of things that get put down the sink (drinks, body fluids, small medical devices, sharps (I’m not even joking – Paz showed a photo of this…, hopes and dreams etc). In fact, one study showed that precisely 4% of the uses of hand washing sinks was for hand hygiene!

Finally, Paz reported the findings of an as-yet unpublished evaluation of sink and drain contamination with CPE in 10 UK hospitals. I was surprised to see that 10% of the sinks were contaminated with CPE (23% with CRE) (I thought this would be lower); Citrobacter and Enterobacter were predominant (together accounting for 60% of the bacteria identified); and patient areas significantly more likely to be contaminated (which is now surprise).

So, what do we do about contaminated sinks and drains? There’s an argument that we should accept that contamination will be there – we use sinks and drains to get risk of contamination with CPE from hands and to dispose of contaminated materials, so we’re not going to stop them becoming contaminated. Instead, we should focus on improving behaviours around the use of sinks and drains to minimise the risk of dispersal (e.g. make sure they’re free-flowing, declutter the sink surrounds, and – here’s a radical idea – use hand hygiene sinks only for hand hygiene). However, there is some evidence that novel engineering solutions and enhanced disinfection can make a pretty impressive reduction in the level of contamination. So, based on current evidence, scant though it is, I think an approach including both looking at ways to reduce the level of contamination through engineering solutions and enhanced disinfection combined with improving human behaviours / workflows around how sinks are used is the best way forward. Oh, and let’s not forget the option to take out sinks altogether in some areas!

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