Pulsed-field gel electrophoresis (PFGE) analysis and dendrogram

PFGE analysis was performed as previously described [35]. Briefly, enterococci DNA embedded in an agarose plug was digested overnight at 25 °C using SmaI (Roche, Basel, Switzerland), and then subjected to PFGE using a CHEF-MAPPER (Bio-Rad, CA) according to the manufacture’s protocol. The guidelines proposed by Tenover et al. were used for the interpretation of PFGE results [36]. The genetic relatedness was analyzed using the Dice coefficient and the dendrogram, and was calculated with the clustering algorithm of Unweighted Pair-Group Method with an Arithmetic Mean (UPGMA) using FP Quest Software (Bio-Rad) [37, 38]. A lambda PFG Ladder (New England BioLabs, MA) was used as the Molecular Marker (MM).