In this era of increasing patient choice, let’s imagine you were offered the choice between two identical looking hospital rooms. Your chances of picking up a multidrug-resistant organism (MDRO) are approximately doubled if you choose the wrong room. But you have no way of knowing which room is safest.

So what explains this lottery? The key information you have not been told is the MDRO status of the previous room occupants. One of the rooms was previously occupied by a patient with C. difficile, and if you choose this room, your risk of developing C. difficile infection doubles. And it’s not just C. difficile – this same association has been demonstrated for MRSA, VRE, Acinetobacter baumannii and Pseudomonas aeruginosa. Underpinning this association is the uncomfortable fact that cleaning and disinfection applied at the time of patient discharge is simply not good enough to protect the incoming patient.

A review and meta-analysis published in the Journal of Hospital Infection neatly summarises the data from these studies. Pooling data from 6 ‘prior room occupant’ studies, 6.2% of 4643 patients  admitted to rooms where the prior room occupant did have an MDRO acquired an MDRO of the same species, compared with 3.2% of 34,886 patients admitted to rooms where the prior room occupant did not have an MDRO. Put another way, this meta-analysis finds that, overall, the increased risk from an MDRO-colonised prior room occupant is approximately 2-fold (odds ratio 2.14, 95% CI 1.65-2.77) (see Figure below, which is not from the study, but gives you a sense of scale).

Figure: Scaling the increased risk from the prior room occupant.

Although poor quality discharge cleaning / disinfection seems to be the smoking gun here, there are other plausible explanations. Patients who are sickest and therefore most likely to acquire an MDRO may be statistically more likely to be placed in a particular bed, under the watchful eye of the nursing station. Similarly, some bedspaces may be inherently less safe than others due to other factors (e.g. cramped conditions, poor access the critical equipment, proximity to handwash sinks). Furthermore, a common criticism of these studies is that molecular typing has rarely been used to ‘cement’ the patient-room-patinet transmission pathways. And when it has, it has ruled out a fair number of apparent patient-room-patient transmissions.

If we were bench scientists trying to prove the role of a particular gene in a process, the accepted way to do this is to knockout the gene and watch the process change or stop altogether. We can apply a similar logic here: if poor quality discharge cleaning / disinfection is really responsible for the ‘prior room occupant’ epidemiological association, then doing a better job of discharge cleaning / disinfection ought to mitigate this increased risk. There are now two studies that put this theory to the test. Datta et al. (which was included in the review) showed that the increased risk of MRSA and to a lesser extent VRE can be mitigated by improving conventional methods. Passaretti et al. (which was not included in the review – for reasons that are not clear to me!) demonstrated that the increased risk from the prior occupant was eliminated altogether by performed discharge disinfection using hydrogen peroxide vapour (HPV). (In fact, in this study, patients admitted to rooms disinfected using HPV were less likely to acquire MDROs even when compared with patients admitted to rooms where the prior room occupant was not known to have an MDRO, probably due to unrecognised MDRO colonisation and MDROs surviving on surfaces from distant room occupants.)

We have known about this association with the prior room occupant for some time – around 10 years in fact. But I don’t think this alarming fact is in the consciousness of many hospital staff – and much less the public. I feel pretty strongly that this is not an acceptable situation: that a patient’s risk of acquisition is influenced by the MRDO status of the previous occupant of their room. And I forecast a storm when the public get hold of this!

Image: Lucky number generator.