The commercially available antimicrobial foil PURZON060B produced by HEXIS S.A. (Frontignan, France) was used for the study. The flexible, transparent and 60 µm thick polyvinyl chloride foil contains an integrated silver-based agent (containing 2% silver ions) developed and manufactured by SANITIZED AG (Burgdorf, Switzerland). Detailed specifications of the antimicrobial foil PURZON060B are provided at https://hexis-graphics.com/documents/fichestechnique/document_en/aut_PURZON060B_FTP_anglais.pdf. Last access June 3, 2021.
The prospective and comparative study was conducted in one surgical and one medical ward at the University Hospital Basel from March through May 2020. Based on a previous study , a reduction of > 50% of the bioburden or important pathogens was considered as clinically meaningful.
On each ward, high-touch surfaces in three patient rooms were coated with the antimicrobial foil. The following high touch surfaces were selected: overbed table, nightstand, armrest of a resting chair, dining table, toilet ring and toilet flusher. The corresponding control surfaces were defined on the same furniture, either adjacent or on the other side (e.g. left and right armrest). The right or left position of the foil or control surface was selected alternately. Since the toilet ring and the toilet flusher had to be fully covered with foil for technical reasons, the controls were taken from an adjacent patient room. Overall, 12 overbed tables, 12 nightstands, 8 armrests, 7 dining tables, 4 toilet rings and 4 toilet flushers were coated with antimicrobial foil, resulting in 47 coated test surfaces and 47 uncoated control surfaces. The self-adhesive antimicrobial foil was applied by trained technicians.
Samples for microbiological investigations were collected every Monday and Wednesday after 5 pm with flocked swabs moistened with NaCl solution prior to use and after swabbing put in eSwab® transport medium (Copan, Brescia, Italy). Guided by clean 25.2 cm2 metal templates, the test foil as well as the control surfaces were swabbed. The swabs were immediately brought to the microbiology laboratory and stored at 4–8 °C overnight before processing.
Out of the eSwab® fluid, 250 µl were inoculated on each of the following culture media: trypticase soy agar, ChromID® CPS® Elite and ChromID® S. aureus Elite (bioMérieux, Marcy-l’Étoile, France). The media were incubated at 36° ± 1 °C for 42–48 h. Colony-forming units (CFU) were counted and suspected pathogenic isolates were identified with matrix-assisted laser desorption/ionization – time of flight (MALDI-TOF) mass spectrometry (MALDI Biotyper®, microflex™ LT/SH smart, Bruker Daltonik, Bremen, Germany). The microbiological analysis focused on the following important pathogens: S. aureus, Enterococcus faecalis, E. faecium, other Enterococcus spp., haemolytic streptococci, Enterobacterales, Pseudomonas spp., and A. baumannii group.
Policy of cleaning and disinfection of the environment
All patient rooms are cleaned once daily with a detergent and single-use microfiber pads. Washrooms are routinely disinfected with Deconex® 50FF (Borer Chemie, Zuchwil, Switzerland), an aldehyde-free certified disinfectant based on ethanedial, pentanedial and didecyldimethylammonium chlorid.
Data was collected in a spreadsheet, imported into and analyzed with Python 3.7.7 (pandas 1.0.3, scipy 1.4.1, numpy 1.18.4). Culture results were reported as log10 CFU /cm2. The mean log10 reduction was calculated as difference between the log10 of the mean CFU of samples taken from the antimicrobial foil and the control surface. The median log10 reduction was calculated respectively. For the comparison between CFU on the antimicrobial foil versus the uncoated control surface, the values were compared by Wilcoxon signed rank test and for nonrelated samples by Mann Whitney U test. P values < 0.05 (two-sided) were considered statistically significant.