Antibiotic Resistance in Food Animals: FDA Takes Strong Stance, But Public Health May Remain At Risk Until Congress Acts

cattle-grazing-usda-copyLeadership at the U.S. Food and Drug Administration (FDA) made it abundantly clear last week that the low-dose usage of antibiotics in food animals, simply to promote growth or improve feed efficiency, needlessly contributes to the emergence of antibiotic resistant bacteria and poses a serious threat to public health. Despite the fact that the FDA is taking a hard-line stance on the issue, I find it frustrating to see that the agency appears to be hamstrung from taking the necessary steps to mandate industry end the risky practice. Even more exasperating is that it appears that the FDA may actually relax a current directive that already regulates antibiotic use. However, unlike many critics, I don’t believe that this is an example of the Obama administration buckling under industry pressure. Rather, I view it as a loud and stern call for Congress to take action. Producers concerned more about profit than protecting public health are not going to cut their dependence on non-therapeutic antibiotic use in food animals unless lawmakers pass strict legislation.

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AVMA Member Hopeful Association Will Revisit Antimicrobial Position

Raymond J. Tarpley, D.V.M., Ph.D.
U.S. industrial animal agriculture routinely incorporates low-dose concentrations of antimicrobials into the feed or water of healthy production animals for the purposes of growth promotion and feed efficiency, an application approved by the U.S. Food and Drug Administration (FDA). This practice selects for resistance among bacteria exposed to antimicrobials, and there has been concern that such resistance could negatively impact public health. Considerable evidence is accumulating that these resistant organisms (and/or antimicrobial residues) move beyond the food animal production operation via 1. food products, 2. soils (upon which animal wastes are applied), 3. water (waste runoff into surface streams and seepage into underground aquifers), 4. crops (antimicrobial uptake from soil), 5. air (blown out of animal holding facilities by industrial tunnel fans), 6. insect carriage (e.g., flies), 7. rodent carriage and 8. human carriage (e.g., farm personnel).

During a time when bacterial resistance to an array of antimicrobials is increasing, renewed attention has been directed toward the threat that resistance arising from low-dose use of antimicrobials on food animal production farms could pose for human and veterinary pharmaceuticals, particularly with fewer novel antimicrobials reaching the market. We now know that resistance to antimicrobials can develop rapidly, extend to other antimicrobials in the same or a different class, and be shared among bacteria through multiple genetic exchange mechanisms within or between genera, culminating in multi-drug resistance in some organisms. While the FDA has recognized the threat that resistance might present, regulatory action has been slow to evolve on this problem, particularly in an atmosphere of industry pushback. Nevertheless, discontinued use of antimicrobials for non-therapeutic use has been called for by the World Health Organization, the World Organization for Animal Health, the Food and Agricultural Organization, the American Medical Association, the American Public Health Association, the American College of Preventive Medicine, the Council of State and Territorial Epidemiologists, the Infectious Diseases Society of America and others. Read More >

AVMA leadership missing key facts on antibiotics in food animals

Dr. Ron DeHaven, CEO and Executive VP of the American Veterinary Medical Association (AVMA)*, spoke last week to the pork industry in Kansas City, MO. DeHaven opposes legislation to ban the use of non-therapeutic (growth promoting) antibiotics and antibiotics with human uses from food animal production. DeHaven used this opportunity to spread misinformation about the reality and consequences of non-therapeutic antibiotic use and food safety.


Early MRSA infections.

DeHaven seems to understand the biological basis for antibiotic resistance, by saying “antimicrobial resistance is caused by widespread use of antimicrobials in food production systems, and hence the more we expose microorganisms to antibiotics the more likely they are to develop that resistance.” The problem arises in his dismissal of the impacts of using antibiotics in food animals—a practice that experts recognize as a public health threat (Silbergeld et al., 2008).

In his talk DeHaven said, “there really is no scientific evidence to confirm just how, if, and to what extent that exposure represents a risk to human health… there has been really no case of human infection with resistant bacteria that has been proven to be caused by the use of antimicrobials in food animals.” This statement is disingenuous and does not acknowledge published findings to the contrary (Voss et al., 2005; Huijsdens et al., 2006) demonstrating MRSA (Methicillin-resistant Staphylococcus aureus) transmission from pigs to a pig farmer, and between pig farmers and their family.

Reported cases of disease are only the tip of the iceberg, therefore we expect that many more cases of community associated (i.e. non-hospital) antibiotic resistant bacterial diseases have originated from factory farms. A recent study in the Journal Emerging Infectious Diseases shows that community associated diseases are increasing at an alarming rate— over 33% increase annually for MRSA in the US from 1999 to 2006 (Klein et al., 2009). While all cases of MRSA may not originate on factory farms, we can’t rule out factory farms and as one source of MRSA (Nunan and Young 2007).

In addition to MRSA, resistant E. coli have been detected in cattle and pigs given antimicrobial drugs (Alexander et al., 2008; Rosengren et al., 2008). When antibiotics are given to food animals, as much as 75% of those drugs are excreted in waste, which contributes to the environmental burden of antibiotic residues and the development of resistant bacteria in the environment (Chee-Sanford et al., 2009). Regulations to reduce or ban antibiotics used in food animals appears to be one clear way we can reduce one source of resistant bacteria.

At the end of his talk, DeHaven takes a stance in support of greater oversight of drug delivery to animals by veterinarians. This would be laudable, except for a giant loop-hole he introduces when saying “veterinary involvement needs to be consistent or proportionate with the risk of those antibiotics.” This insinuates that continuing the practice of selling antibiotics over-the-counter (OTC) in feed to farmers, with no veterinary oversight, is acceptable. The AVMA is investigating other ways of relaxing food animal veterinary oversight, with increased involvement of veterinary technician and electronics prescriptions of antibiotics. With region-specific shortage of mixed animal veterinarians in the US, can you blame the AVMA for feeling squeamish about its options for taking care of the burgeoning numbers of food animals? Read More >