Methods

Over five afternoons in May and June 2022, one hundred consecutively selected voluntary HCWs were interviewed, and microbiological samples of their used attire were collected upon return to the automated clothing delivery and disposal system. The interview consisted of a standardized electronic survey on a laptop provided on-site; the collected data were automatically transmitted to a dedicated Research Electronic Data Capture (REDCap) database. The survey contained details on use of the respective work attire, clinical department, and distance from their workplace to the clothing delivery system. In parallel, a physician and a nurse from the infection prevention and control unit performed standardized microbiological sampling on the outermost layer of each used attire set using Eswab® Collection kit Regular (Becton Dickinson, Eysins, Switzerland) at a maximum of four sampling sites across four types of attire, all made of cotton including scrubs, pocketed coats, and two types of pocketless polo shirt (Figure 1). Swabs were applied in a Z-shaped line once horizontally and once vertically within a 10 x 10 cm area, which was delimited using a template for standardization. Samples were cultured on selective plates, incubated for 48 hours at 35 °C, with CO₂ supplementation when required. Bacterial growth was semi-quantitatively scored from 1 to 4 crosses following standard laboratory protocols, identified by MALDI-TOF, and tested for antibiotic susceptibility using the Kirby-Bauer method according to EUCAST criteria. Possible skin contaminants were identified according to guidance from the Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) Patient Safety Component Manual. ⁷ Fungi were excluded from the analysis. At Bern University Hospital, the laundry exchange process is fully automated: HCWs can retrieve new clothing and return used attire at a dedicated automatic delivery system, which are subsequently laundered by an external company using a standardized process (60 °C for 50 mins). The formal recommendation at our institution is to change work clothing daily, or immediately if visibly soiled, but no monitoring of compliance is performed. Unlike practices in some other countries, wearing or washing work attire outside the premises is not permitted. Our primary objective was to perform a descriptive analysis of the participants and to illustrate the distribution of bacterial contamination at different locations on HCW attire. Our secondary objective was to use uni- and multivariate logistic regression models to identify factors associated with the frequency of attire changes (end point: changing attire on the same day) and contamination with clinically relevant pathogens. Variables were included via forward selection and then backward deletion, with p < 0.1 as the inclusion criterion. Variables were checked for collinearity before inclusion in the model. All analyses were performed with R (version 4.0.2). A P value < 0.05 was considered statistically significant.

Figure 1. A. Representation of the number of samplings with evidence of growth of at least one pathogen at the four sites B. Total count of all individual microorganisms detected per site (a single site can show growth of more than one pathogen and skin  commensal). At the site “sleeve, wrist height”, no growth was detected in 2 samples (not shown on the graph for the sake of compression). The hatched area indicates the sampled zone. The asterisk (*) denotes the dominant side.