Many organizations and agencies, including the Canadian Veterinary Medical Association, have developed or are developing prudent use guidelines to cover all antimicrobial usage. If bacteria acquire resistance to more than one antimicrobial they are called multiple resistant. Although these two terms are often used interchangeably, technically there is a difference. Antibiotics are natural substances produced by microorganisms that, at low concentrations, are able to inhibit or kill other micro-organisms. Antimicrobials are any natural, semi-synthetic or synthetic substances, including antibiotics, which inhibit or kill microorganisms without harming the host.
Antimicrobial resistance is an issue worldwide.
In 1986, Sweden banned antimicrobials in feed for the purpose of promoting animal growth. In December 1998, four additional antimicrobials were added to the EU's list of banned substances for inclusion in livestock feed. This brings the number to 16 drugs banned by the EU on the basis of managing health risks, including antimicrobial resistance. In the U.S., the Food and Drug Administration is proposing changes in how some antibiotics can be used in veterinary medicine as well as changes to the approval process for new antimicrobial drugs. Health Canada is responsible for the approval and registration of all antimicrobials for use in agriculture.