A New Look at Antibiotic Resistance

In response to the widespread use of antibiotics in animals raised for food, not only for disease treatment but also for prevention and growth promotion, governments have stepped in to reduce the practice to therapeutic use only and combat antibiotic resistance. While this has provided some positive outcomes, there are a number of other considerations that should be kept in mind as well, namely ensuring that consumers — who are driving the initiative toward “No Antibiotics Ever”— truly understand the issue, and addressing the fact that overuse of antibiotics in humans also has contributed to antibiotic resistance.

In a recent TAG newsletter, I discussed the latest report on the U.S. National Antimicrobial Resistance Monitoring System (NARMS) program, which highlights antimicrobial resistance patterns in bacteria isolated from humans (by CDC), raw retail meats (by FDA), and animals at slaughter (by USDA). In brief, the 2015 report showed that overall resistance remains low for most human bacterial infections, and there have been measurable improvements in resistance levels in some key areas. For example, from 2014 to 2015, the proportion of retail ground turkey isolates resistant to at least one antimicrobial declined from 73% to 57%. Additionally, 76% of Salmonella isolated from humans had no resistance to any of the 14 antimicrobial drugs tested.

However, the report also showed some negatives, e.g., multidrug resistance increased from 9% to 12% of human  Salmonella, and between 2011 and 2015, and erythromycin resistance in  Campylobacter coli increased from 2.7% to 12.7% in isolates from humans and 3.4% to 12.8% from chicken carcasses.

Interestingly, just as FDA’s use of whole genome sequencing (WGS) has increased in its testing of environmental samples from food facilities, the WGS method also was recently incorporated into NARMS, enabling resistance genes to be tracked over time. Because NARMS research has shown that antibiotic resistance can be predicted reliably from the genomic sequence, FDA is developing tools to make these large data sets easier to understand.

It also will be interesting to see the results of the next NARMS report, which should show an impact of FDA’s Guidance for Industry #213, which called for the voluntary removal of growth promotion indications from the labels of medically important antimicrobial products used in the feed or water of food-producing animals and bringing the remaining therapeutic uses under veterinary oversight. The guidance was introduced in December 2013 and was due to take full effect by January 1, 2017.

THE UK EXAMPLE. But the U.S. is not the only government which has turned its attention to antibiotic use — it’s not even the most successful. A report published in late October by the UK government cited a 27% drop in use of antibiotics in food-producing animals in that country since 2014. The reduction from 62 mg/kg in 2014 to 45mg/kg in 2016 brought sales to their lowest level since records began, and exceeded the government target of 50 mg/kg two years early. Additionally, sales of antibiotics considered critically important for human health dropped, accounting for less than 1.0% of all antibiotics sold for use in animals in 2016.

The reductions were the result of a  UK government strategy  launched in 2013 to reduce the development and spread of antibiotic resistance in animals and humans. As part of the strategy, the government has provided expert advice to the farming industry and veterinary profession, encouraging more responsible use of antibiotics to safeguard them for the future.

While I would never disparage such positive results, I do believe we need to take care in communicating with consumers the issues of, and potential solutions to, antimicrobial resistance. There is no doubt that consumers are driving the trend in “Antibiotic Free” and “No Antibiotics Ever,” but I believe that consumers totally misunderstand this whole issue and are confusing residual residue of antibiotics in meat with the overall use of antibiotics.

Reducing antibiotic use in animals, ensuring only therapeutic use with veterinarian oversight, and assuring that producers are following regulations for drug withdrawal periods maximum  residue limits  (MRLs) are of increased importance today, but it is no more practical to completely ban antibiotic use for animals than it is to do so for humans. Like humans, animals get sick and, in some cases, require antibiotics for treatment and to not infect the entire flock or herd.

THE HUMAN FACTOR. That said, we do need to limit antibiotics to necessary, therapeutic use — in animals and humans. Too often, the human factor is overlooked in antibiotic-resistance discussions, but that overuse is just as responsible for today’s issues as is that for animals. In fact, the UK report notes the human factor as having greater culpability, stating, “Increasing scientific evidence suggests that the clinical issues with antimicrobial resistance that we face in human medicine are primarily the result of antibiotic use in people, rather than the use of antibiotics in animals.”

That doesn’t mean that animal use is to be let off the hook, of course. And while the U.S. has taken steps and begun to see reduction, I think we also should take a good, hard look at the UK programs. Its 27% reduction in use of antibiotics in food-producing animals in two years is highly commendable. And nowhere in its standard is it saying to eliminate antibiotic use to “No Antibiotics Ever,” rather it acknowledges that “Modern medical and veterinary practice relies on the widespread availability of effective antimicrobials to prevent and treat infections in humans and animals.” And its goal is that of “ensuring that antibiotics are used responsibly and less often” to “conserve and steward the effectiveness of existing treatments.”