Antimicrobial susceptibility of vancomycin-susceptible and -resistant enterococci isolated in Italy from raw meat products, farm animals, and human infections

The susceptibility of vancomycin-resistant (VRE) and vancomycin-susceptible (VSE) enterococci to 10 antimicrobial agents was evaluated. The strains, belonging to different species, were isolated in Italy from raw meat products, farm animals, and human clinical infections in the years 1997–2000. High frequency of resistance to tetracycline and erythromycin was observed in all the groups of strains. On the contrary, chloramphenicol was the only drug that showed a relatively low rate of resistance in all the groups examined. In general, the resistance rates observed for VSE did not differ from those observed for VRE of the same species and origin. Some differences could be noticed among the different enterococcal species, with Enterococcus faecium strains being usually more resistant to beta-lactams, and Enterococcus faecalis strains more resistant to gentamicin. However, the strongest differences were observed when the strains were compared according to their source, the human isolates being usually more resistant than the isolates of animal origin. No significant difference was observed between isolates of swine and poultry origin. Among VRE E. faecium, multiple resistance was much more frequent among the human strains (90%) than among poultry (48.9%) and swine (26.5%) strains. These results show that in Italy VRE isolates from human clinical infections are usually more resistant than isolates from meat products and farm animals, and possess different antimicrobial resistance profiles.