Mythematics: Distorting data for shock value
This is a guest post written by Karin Schmid, Beef Production Specialist with the Alberta Beef Producers, in collaboration with Dr. Reynold Bergen, BCRC Science Director.
Everyone loves a good statistic, and it is surprisingly easy to warp data to fit a particular message. It happens time and again, slandering beef production on animal welfare, public health and environmental issues, and most recently around the topic of antimicrobial resistance.
Misleading data on antimicrobial resistance
Earlier this month the Environmental Working Group (EWG) released a report on antimicrobial resistance in retail meat samples. The report referred to research conducted by the National Antimicrobial Resistance Monitoring System (NARMS), which is similar to our Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). The EWG report states “government tests of raw supermarket meat published last February 5 detected antibiotic-resistant bacteria in 55% of ground beef.”
The 55% refers to 263 out of 480 ground beef samples that contained Enterococcus faecalis bacteria resistant to at least one antimicrobial. E. faecalis is a gram-positive bacterium that lives in the gastrointestinal tracts of humans and other mammals. It can cause serious infections in humans, including endocarditis, bacteremia, urinary tract infections and meningitis, among others. It is the most common Enterococcus bacterium found in ground beef.
The rest of the story
What the EWG report does not mention is that the 263 ground beef samples resistant to one antibiotic were resistant to lincomycin. E. faecalis is naturally resistant to that antibiotic. In fact, CIPARS does not measure resistance to lincomycin in enterococcus because E. faecalis would naturally be resistant to lincomycin even if it was never exposed to that particular drug.
In fact, when you look at the drugs that should affect E. faecalis, the NARMS report found no resistance to drugs of “Very High Importance” in human medicine and less than 2% demonstrated resistance to more than three classes of antimicrobials. The highest level of resistance (18.2%) for E. faecalis was to tetracycline, which is used to treat acne in people.
The NARMS report found similar results for E. coli; fewer than 1% were resistant to drugs of “Very High Importance” in human medicine and less than 2% were resistant to more than three classes of antimicrobials. Nearly 80% of E. coli isolates were susceptible to all antimicrobials tested. The NARMS data also show that levels of resistance to antimicrobials in retail beef samples from 2002-2011 in both enterococcus species and E. coli has been relatively stable and declining in some cases.
This U.S. data supports what we have discovered in Canada both through the Public Health Agency of Canada’s CIPARS and through research supported by Alberta Beef Producers (ABP) and the Beef Cattle Research Council (BCRC).
Canadian data from industry funded studies show that less than 1% of E. coli isolates collected from feedlot cattle are resistant to drugs of “Very High Importance” in human health, and less than 8% are resistant to more than three antimicrobials.
Healthy Cattle Prior to Processing
CIPARS has also found that less than 1% of E. coli isolates collected from healthy cattle entering Canadian processing plants are resistant to drugs of “Very High Importance,” and less than 2% are susceptible to more than three antimicrobials.
CIPARS data demonstrates that E. coli resistance in retail beef to drugs of “Very High Importance” is also below 3%, and fewer than 3% are resistant to more than three antimicrobials.
Further research proposed under the second Beef Cattle Industry Science Cluster will compare the precise genetic fingerprint of resistant bacteria isolated from cattle with resistant bacteria isolated from sick people to compare if those genetic mechanisms which cause resistance are related, although this will not confirm if resistance is being transferred from cattle to humans or vice-versa.
Misleading data on antimicrobial use
It is often quoted that “80% of antimicrobials sold in the United States are used in food producing animals, and the vast majority of this use is for animals that are not sick.”
This statistic compares two sets of data that are not comparable. The number estimated for animal use is based on different methodology than the estimate for human use. In addition, 45% of that animal use calculation is comprised of drugs not used in human medicine, such as ionophores and other compounds not approved for use in humans. The largest class of antibiotics sold in 2010 for animal use was tetracycline (42%), while tetracycline use in human medicine accounts for about 1% of the total amount sold based on weight. In actuality, the statistics show 87% of antibiotics used in animals are either never, or very rarely, used in human medicine.
The U.S. Food and Drug Administration (FDA) clearly warns against comparing the human and animal data on their website.
Putting data into context
Even when the information is technically correct, the interpretation of that information is critical to a thorough understanding of the issue at hand. While the statistics stated by the EWG are accurate, the report is misleading. The fact that E. faecalis is naturally resistant to lincomycin should have been communicated to the public. It is also deceptive to include antimicrobials that are never used in human medicine in a discussion about human health.
When drawing a conclusion based upon statistics, it is crucial to ensure that the facts and statistics used to back up a certain position are not twisted to provoke a false belief.
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