The guidelines also recommend limiting performance claims – increased rate of weight gain and improved feed conversion, for instance – to certain antimicrobials that are never or rarely used in human medicine.

How does FDA determine which antimicrobials are “medically important”? Basically, the agency asks five questions about each antibiotic:

1. Is it used to treat enteric pathogens that cause foodborne disease in humans?
2. Is it the sole therapy or one of few alternatives to treat serious human disease or a drug that is an essential component among many antimicrobials in treatment of human disease?
3. Is it used to treat enteric pathogens in non-foodborne disease?
4. Is there cross-resistance within the drug class or linked resistance with other drug classes?
5. How easily does resistance to a drug cross over to other genera and species of organisms?

Making the Grade

If the answer to questions 1 and 2 is yes, the antimicrobial is considered “critically important”. If either question draws a nod, the antimicrobial is considered “highly important”. If the answer to questions 1 and 2 is no, but yes to questions 3, 4 or 5, the antimicrobial is rated “important” to human health. All other antimicrobials are considered non-medically important.

Under the new guidelines, producers will be advised to obtain a VFD order before any medically important antibiotics are used in poultry, and then these antimicrobials should only be used to prevent, control or treat a disease indicated on the product label.

A list of FDA’s current rankings of commonly used poultry antimicrobials in available online from Poultry Health Today [click here].

FDA insists this list is “not static”, however, and that it will periodically be updated as necessary, taking into consideration such factors as the development of new antimicrobials for human therapy, the emergence of diseases in humans or changes in US prescribing practices.