Gp cards

Species identification was performed using the Vitek 2 Compact automated system and GP cards (Biomerieux, Marcy l’Etoile, France). S. aureus methicillin resistance was detected by the disc-diffusion method using cefoxitin discs (Becton Dickinson, New Jersey, NJ, USA), as recommended by EUCAST (version 8.1). S. aureus isolates were stored in freezers (−70 °C) for further analysis using TSB (tryptic soy broth; BTL, Warszawa, Poland) containing 50% glycerol (POCH, Gliwice, Poland).

Samples were collected from the tested surfaces (25 cm²), inside of a tap, drain traps and drain gratings using sterile swabs moistened in a sterile NaCl solution and/or using contact plates (Oxoid, Wesel, Germany). Identification to the level of genus was possible based on microscopic and macroscopic assessment of bacterial colonies as well as biochemical tests: ID Color Catalase (BioMérieux, Marcy-l’Étoile, France)—the reagent detects the presence of catalase, thus enabling the differentiation of bacteria that possess this characteristic, Bactident Oxidase test (MERCK, Darmstadt, Germany)—for the detection of cytochrome oxidase in microorganisms. Identification of the isolated strains to the level of species was carried out using an automatic identification system VITEK^® Compact 2 (BioMérieux, Durham, NC, U.S.). GN cards (BioMérieux, Durham, NC, U.S.) were used for identification of Enterobacterales and a select group of nonfermenting Gram-negative organisms, GP cards (BioMérieux, Durham, NC, U.S.) were applied for the identification of enterococci, streptococci, staphylococci and a selected group of gram-positive organisms. All identified strains were stored for further tests in temperature −80 ± 10 °C, in microbanks (Pro-Lab Diagnostics, Richmond Hill, ON, Canada).