Withdrawal of growth-promoting antibiotics in Europe and its effects in relation to human health.

The glycopeptide avoparcin, bacitracin, the macrolides spiramycin and tylosin, and the streptogramin virginiamycin were withdrawn as growth promoters in the European Union between 1995 and 1999 on the basis of the Precautionary Principle. Relevant resistance thereupon diminished among enterococci (the indicator organisms) isolated from animal and human faeces. However, animal enterococci were shown to differ from those that caused human infections, although their resistance genes were sometimes indistinguishable and thus probably have a common origin. Before the ban, human clinical isolates of enterococci resistant to vancomycin or teicoplanin were uncommon in many, but not all, parts of Europe and resistance to quinupristin/dalfopristin in the case of Enterococcus faecium was very rare. After the ban, these resistances increased in prevalence almost universally, to the detriment of human health. Campylobacters, normally susceptible to macrolides, increased in prevalence before and after the ban. Analyses suggest that the added risk to human health from resistance among enterococci and campylobacters selected by growth promoter use is small, whilst the benefit to human health from their use, hitherto largely ignored, might more than counterbalance this.