The human health implication of the use of antimicrobial agents in animal feeds.

ABSTRACT

Antimicrobials given in subtherapeutic levels in feed are credited with having contributed to lower cost of meat, milk and eggs. The practice often is associated with the acquisition of resistant enteric flora by the involved animals, and this may in turn contribute to the human reservoir of antimicrobial resistant coliforms and salmonellae. Associated farm workers may transiently acquire resistant flora and on rare occasions develop salmonellosis. Although irrefutable evidence of growth promotant properties of antibiotics in animal feed was provided 30 to 40 years ago, additional studies on mechanisms of the effect are presently needed. It may be possible to identify factors effective in promoting growth without deleterious effects on flora. A national surveillance programme of antimicrobial utilisation (both subtherapeutic and therapeutic) among food producing animals should be established. Molecular epidemiologic research efforts will need to be undertaken to establish whether genetic information of animal origin importantly contributes to the human environmental pool of antimicrobial resistance. In the meantime, it does not appear that the use of drugs as feed additives, while allowing their unrestricted use for therapy in both animals and persons, would favorably influence the problems of antimicrobial resistance of salmonellosis in human populations.