Disease-causing bacteria are becoming more resistant to antibiotics, a fact many blame on the food animal industry.
As human resistance to antibiotics grows, you pay the price
The trend lines are clear: Across the globe, there are disease-causing bacteria in humans that are becoming increasingly resistant to antibiotics.
To be sure, overuse and inappropriate use by doctors and their patients is largely to blame. But a finger is also increasingly being pointed at agriculture—particularly the industry’s nontherapeutic use of antibiotics for growth promotion and feed efficiency.
While there is little such use in milk production, especially in lactating cows, the dairy industry is not immune from pressure. Routine use of antibiotics in replacement dairy animals is one target of new drug regulations.
The fear of resistance is both real and growing, said microbiologists speaking at the Antibiotic Use in Food Animals conference in Chicago in October. The conference was sponsored by the National Institute for Animal Agriculture to promote dialogue between groups that support and oppose antimicrobial use in agriculture.
In the U.S., methicillin-resistant Staph. aureus (the dreaded MRSA) has grown from 27% of samples in 1997 to 51% in 2009. Over the past decade, resistance to penicillin in Europe has jumped from 10% of samples to 15%. In the Asia-Pacific region, it has almost doubled, from 18% to 32%, reports Robert Flamm, a microbiologist at JMI Laboratories in North Liberty, Iowa.
Antimicrobial resistance is complex, and even microbiologists admit they don’t fully understand all the underlying mechanisms. In its simplest form, however, resistance is merely selection. Antimicrobials kill susceptible bacteria, allowing resistance bacteria, though small in number, to survive and multiply.
More complex resistance occurs when resistant bacteria share their DNA with other microbes, which can be totally unrelated.
Livestock is in the crosshairs because of the amount of antimicrobials used on farms. On a tonnage basis, livestock producers use the majority of antibiotics.
In the U.S., for example, 28.8 million pounds of antibiotics were sold for animal use in 2009, according to a survey by the Food and Drug Administration (FDA). Roughly 11 million pounds of that amount, or 38%, were ionophores, which are not considered a threat in human drug resistance.
Even so, the remaining 17 million to 18 million pounds represent 60% to 70% of all drugs sold that are a concern on the human health side. That’s a huge number.
As a consequence, FDA is moving forward with guidance documents that will eventually eliminate the use of "medically important" antimicrobials for growth promotion and feed efficiency. Ionophores will not be included in this group, says William Flynn, deputy director for science policy at FDA’s Center for Veterinary Medicine in Rockville, Md.
But the new guidelines will mean much more judicious use of antimicrobials that are administered through feed or water. The drugs will be used only for the treatment, prevention or control of disease, and a licensed veterinarian will have to be involved.
"FDA acknowledges that this could result in an increase in animal disease, and we therefore need to be able to address this concern," Flynn says.
- December 2011