Detection and Characterization of Vancomycin-Resistant Enterococci in Farm Animals and Raw Meat Products in Italy

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Abstract
The emergence of vancomycin-resistant enterococci (VRE) in Europe has been ascribed to the long-time use of the glycopeptide antibiotic avoparcin as feed additive in food animals, until its ban in 1997 in EU. The presence of VRE in food of animal origin is believed to represent a potential risk for the consumer. We studied the fecal carriage of VRE in broiler chickens and slaughter pigs in Italy before the avoparcin ban and evaluated the impact of avoparcin withdrawal on the presence of VRE in raw meat products. Broilers and pigs were both found to be frequently colonized by VRE, as 36% and 24.6% of the flocks or the herds, respectively, were positive. Molecular typing of VRE strains by PFGE showed that animals housed in different pens within the same farm were colonized by clonally related strains. After the avoparcin ban, a decrease in the rate of VRE contamination in meat products was observed. Such a decrease was statistically significant in poultry (from 18.8% to 9.6%) but not in pork products (from 9.7% to 6.9%). The majority of VRE from all sources carried the vanA resistance gene and included Enterococcus faecium, E. faecalis, E. hirae, E. durans, and E. gallinarum. None of the strains carried the vanB gene, whereas constitutively resistant vanC-positive strains were frequently found. Our results show that avoparcin withdrawal has been successful in reducing VRE contamination in meat products. However, this measure needs to be complemented by a prudent use of glycopeptide antibiotics in human medicine.