Study design graphic representation.

Six Italian hospitals from different geographical regions were enrolled in the study (North: Feltre, Tolmezzo, Vigevano; Centre: Rome; South: Foggia, Messina). Five hospitals were randomly allocated in two Intervention groups (I₁, I₂) and one further hospital represented an external control (_extC): I₁-group included Roma, Foggia and Feltre hospitals, entering the study on January 1^st 2016; I₂-group included Vigevano and Tolmezzo hospitals, entering 5-months later, on May 1^st 2016; _extC hospital was represented by Messina hospital, receiving no intervention and monitored from May 1^st 2016. The phases of the study are indicated by colours: orange, 6-months pre-intervention period (pre-PCHS); light green, stabilization period, when PCHS was introduced; green, 6-months post-intervention period (PCHS), when PCHS was routinely applied. Sampling campaigns for microbiological analyses are indicated by circles: conventional microbiological analyses were performed monthly (black circles), and molecular analyses were performed quarterly (red circles) in all enrolled hospitals.