Glycopeptide resistance in Enterococcus faecium from broilers and pigs following discontinued use of avoparcin

The use of the glycopeptide growth promoter avoparcin was discontinued in D enmark in 1995 following concerns that vancomycin-resistant Enterococcus fa ecium occurring as a result of its use could be transferred to humans via f ood. The present study is an analysis of results obtained by the continuous surveillance of an antimicrobial resistance in Denmark (DANMAP) with the a im of determining the effect of the ban on the occurrence of glycopeptide r esistance among E, faecium isolated from broilers and pigs, Among isolates from broilers, the proportion that were resistant to glycopeptides has show n a statistically highly significant decline between the end of 1995 and th e first half of 1998, whereas in pigs the ban appears to have had no such e ffect. One possible explanation is that the broiler industry generally uses all in-all out production compared with continuous production in pig herds . Alternatively, the results indicate that the different outcomes may resul t from different co-selection patterns in pigs and broilers. In pigs, the a ntimicrobials most commonly used favored co-selection of glycopeptide-resis tant strains of E. faecium while in broilers the antimicrobials most widely used selected for glycopeptide-susceptible strains. The results show that intervention to reduce antimicrobial resistance may not always be effective and preventing resistance problems therefore becomes essential.