The use of antimicrobial agents is likely to lead to selection of resistance whether administered to humans, animals or plants. Zoonotic organisms such as non-typhoid Salmonellae, Campylobacter spp. and enterohaemorrhagic E. coli (e.g., O157) can, by definition, be transferred to humans from animals. Therefore, it stands to reason that resistant zoonotic organisms can also be transferred to humans. The transfer of antimicrobial-resistant non-zoonotic bacteria or their genetic material from animals to humans via the food chain is also possible. However, data demonstrating the magnitude and importance of such transfer and whether such transfer occurs via consumption of contaminated meat or via contamination of water or vegetables by animal excreta are limited. Humans are also a potential reservoir of antimicrobial-resistant microorganisms.

The extent to which food-producing animals contribute to human exposure to antimicrobial-resistant microorganisms is difficult to quantify. However, when evaluating the safety of antimicrobial products for use in food-producing animals, regulatory authorities should consider the potential for such products to select for resistant bacteria. Therefore, guidance is needed for drug sponsors on the type of information that should be provided to the regulatory authorities. This information should help to characterize the potential for the use of the product to select for antimicrobial-resistant bacteria of human health concern. The information provided should be used as part of an overall assessment of the potential impact of the product on human health.

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