Indentification of gene or genes causing the plasmid-mediated narasin-resistance in broiler isolates of E. faecium.. Narasin resistance in Enterococcus faecium

The polyether antimicrobial substance Narasin is used as a coccidiostat in broilers. Enterococcus spp. have been isolated that are resistant to the substance and it has been proposed that this resistance maintains the vancomycin resistance also often seen in broiler isolates, although no vancomycin is used. The narasin resistance has been showed to be tranfereable with plasmids in a conjugation experiment. By sequencing both narasin-resistant and narasin-susceptible transconjugants the genes responsible for this were identified. It was found to be caused by an ABC-transporter system of two genes.