Continuing high prevalence of VanA-type vancomycin-resistant enterococci on Norwegian poultry farms three years after avoparcin was banned

Avoparcin was used as a feed additive in Norwegian broiler and turkey produ ction from 1986 until 1995. It was banned due to the selection of VanA-type vancomycin-resistant enterococci (VRE) in animal husbandry and to reduce t he potential for human exposure to VRE. The aim of the present study was to investigate the prevalence of VRE carriage in Norwegian poultry farmers an d their poultry three years after avoparcin was banned. Corresponding faeca l samples from poultry and humans on farms where avoparcin had previously b een used (exposed farms, n=73) and farms where avoparcin had never been use d (unexposed farms, n=74) were analysed for the presence of VRE. For each f arm, one sample from the poultry house and one sample from the farmer were obtained. VRE were isolated from 72 of 73 (99%) and eight of 74 (11%) poult ry samples from exposed and unexposed farms, respectively. VRE were isolate d from 13 of 73 (18%) and one of 74 (1%) farmer samples from exposed and un exposed farms, respectively. All VRE isolates were highly resistant to vanc omycin and possessed the vanA gene, as shown by PCR. The high prevalence of VRE is in accordance with previous Norwegian studies, and shows a remarkab le stability of the VanA resistance determinant in an apparently non-select ive environment.