Supplementary Material 6.Details on the decolonization strategy, outcome, and more detailed financial consequences.

Regarding the choice of the assessed decolonizing agent, octenidine works well on MRSA [1-4] even in presence of mupirocin resistance. Mupirocin resistance is well established [5], is increasing in incidence, and contributes to decolonization failure, although direct comparisons of the decolonizing effects of mupirocin and octenidine are lacking. In turn, octenidine resistance has not been described for MRSA and octenidine shows better activity in MRSA biofilms than mupirocin [6]. In previous studies, octenidine-based decontamination in the nostrils was reported to be associated with decolonization success in two out of three patients [7, 8]. To the authors’ best knowledge, there is no study directly comparing the decolonizing effects of mupirocin and octenidine in the nostrils.

In addition, octenidine is used in Rostock for body surface decontamination and, therefore, the noseointment is in line with the remainder of the decolonization procedure. While mupirocin is applicable to the nostrils, mucous-membrane-compatible disinfectants have to be used for the throat anyway.

Poor decolonization rates as observed in this study have been described previously as compliance-dependenteffects [9]. Further reasons in this study includeswab acquisition by staff trained for screening, with resulting increased detection rates [10], and the use of optimum swab material [11].

Re-introduction of failed patients during initial decolonization into another round of decolonization isconsistent with current German MRSA precaution guidelines by the Robert Koch Institute from 2014 [12];however, it contradictsre-imbursement regulations thatinclude a standard time range for hospitalization. The secondround is no reason for keeping the patient in the hospital. A second round performed by the general practitioner can only be suggested by the hospital staff and, due to lack of information flow, cannotbe followed up by them.

Cost calculations may vary depending on national requirements and would go beyond the scope of this study. Cohort isolation of MRSA carriers would modify the costs as opposed to single-room isolationmeasures. Yet, the prevalence of MRSA carriers among the local population of Rostock is low (1 to 1.2%according to the unpublished results of the joint HiCare project) so there are hardly ever two or more MRSA carriers simultaneously present on one ward, which renders cohort isolation impossible.

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