The primary outcome of this study was transmission of ESBL-producing Enterobacteriaceae to wardmates, which was defined as rectal carriage of an ESBL-producing Enterobacteriaceae isolate that was clonally related to the index patient's isolate in at least one wardmate. The primary analysis was done in the per-protocol population, which included patients who were adherent to the assigned room type. A 10% non-inferiority margin for the risk difference was used to assess non-inferiority. The results indicate a crude risk difference 3·4%, with a 90% CI ranging from 3.1% in favour of multiple bed rooms to a 7.1% difference in favour of single rooms. Therefore because a difference of 10% was ruled out within the confidence interval the authors concluded that multiple bedded rooms were non-inferior to single rooms in preventing transmission.
In a related editorial the authors note several limitations – including no assessment of compliance with hand hygiene, the fact that screening occurred within 7 days after known exposure which could lead to underdetection of colonisation, high rates of non-adherence to allocated room and the fact that a 10% non-inferiority margin was quite large compared with the observed rate of transmission in the single room (5%). The authors also question the generalisability of the findings beyond healthcare settings with high hand hygiene compliance, a high quality of environmental cleaning, and a low prevalence of ESBL-producers that are not Escherichia coli