Fig. 1

a Schematic representation of reprocessing procedures in dental care: critical steps (modified from [19, 20]); proposed sampling points are reported to monitor the different phases. Transport and decontamination are critical to assure both instrument and operator safety. They are performed by validated protocols and registered chemicals, following official guidelines or hospital approved protocols; cleaning by a washer-disinfector or manual steps is essential to remove those traces that could inhibit the sanitation efficacy. Inspection is visually performed by a magnifying device and is required to evaluate residual particulate contaminants, salt deposits or marked discolorations. Sterilization (autoclaving 121 °C for 30 min) is preceded by a packaging process. Dotted lines indicate sampling points for the monitoring of process main steps; b Sampling and analysis of mfDNA. In accordance with previously described protocols [23, 24], moistened sterile swabs were used to sample target surfaces. After washing in a PBS buffer, the bacterial wall was disrupted by glass beads using a mechanical pestle. DNA was purified by conventional kits and analyzed by real Time PCR