These bacterial strains were kindly supplied by Synbiotec S.r.l., Spin-off of Camerino University (Camerino, Italy), as freeze-dried commercial probiotics. They were isolated from fecal samples of Italian elderly subjects during an EU project named Crownalife, as previously described (Verdenelli et al., 2009). L. rhamnosus IMC 501® and L. paracasei IMC 502® have been studied for their probiotic properties such as gastro-intestinal transit (acid and bile tolerance), in vitro adhesion to cell line, antimicrobial activity, antibiotic susceptibility,plasmid profile and in vivo colonization and persistence on human gut