dalfopristin, an approved antimicrobial for use in humans (McDonald et al., 2001). The researchers believed that the use of virginiamycin, an antibiotic of the streptogramin group, in farm animals had created a reservoir of streptogramin–resistant E. faecium in the food supply, which could contribute to foodborne dissemination of resistance as the clinical use of quinupristin–dalfopristin increases.
Substantial evidence supports that certain types of resistant organisms, such as vancomycin-resistant enterococci, emerged initially in animals because of the use of similar drugs for growth promotion or prophylaxis (O’Brien, 2002). Consideration of this association led to a ban on the use of avoparacin, a vancomycin analogue, in Europe (Wegener et al., 1999). The decreased use of antimicrobials for growth promotion or prophylaxis in many European countries has been associated with a subsequent stabilization in resistance or a gradually decreasing resistance in animal flora (Aarestrup et al., 2001). WHO has called for all antimicrobials used for disease control in food animals to be prescribed by veterinary health care providers, and for termination or rapid phase-out of antimicrobials used for growth promotion if they are used for human treatment (WHO, 2000f). Various other groups have suggested that because of the increasing risk of antimicrobial resistance, the subtherapeutic use of antibiotics for growth promotion should be banned (some would include use for prophylaxis in the ban as well) if they are also used in humans (Union of Concerned Scientists, 2002; Alliance for the Prudent Use of Antimicrobials, 2002).
The main argument against a ban is the potential economic hardships to livestock and poultry producers, which would result in higher costs for consumers. According to the IOM Committee on the Use of Drugs in Food Animals, such a ban would increase the price of meat by an estimated 0.013 to 0.06 cents per pound; this translates to $4.84 to $9.72 per person each year, depending on the meat and the cut (IOM, 1999b). Yet, evidence suggests that animals can be raised efficiently without the use of growth-promoting antimicrobials (Emborg et al., 2001; Wierup, 2001).
Critics of the ban also argue that it would result in poorer production efficiency and an increased incidence of infectious disease in animals. However, it has been noted that subtherapeutic antibiotics are most effective in animals under the stress of inadequate nutrition and suboptimal sanitary conditions (Braude et al., 1953); therefore, improved hygiene and changes in animal husbandry practices to control disease could potentially eliminate the need for growth promoters (Emborg et al., 2001). In Denmark, the elimination of antimicrobial growth promoters from broiler chicken feed did not result in a change in death rates or a decrease in kilograms of broilers produced per square meter. Danish scientists also reported that the decreased use of virginiamycin and avilamycin in animals was followed by decreases in resistance to these drugs (Aarestrup et al., 2001).