The role of perspective in evaluating science

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Last week’s conference in Kansas City, titled “Bridging the Gap between Animal Health and Human Health,” helped advance a dialog between animal agriculture, human medicine, public health and consumer groups regarding antibiotic resistance. It was clear though, that the dialog will need to accelerate before we can expect any semblance of consensus or progress toward resolving the issue of how antibiotics should or should not be used in animal agriculture.

The conference, hosted by the National Institute for Animal Agriculture (NIAA), featured an impressive array of speakers including medical doctors, veterinarians, other scientists, retailers and representatives of consumer-advocacy groups and meat companies. Individual speakers outlined the science behind antibiotic resistance, government and industry efforts to monitor antibiotic use and resistance, regulatory measures and consumer perceptions of the issue, which often have little or nothing in common with the science behind the issue. Science alone will not “bridge the gap” on this issue.

But even among scientists with the technical background to conduct and evaluate research into the causes of antibiotic resistance struggle with inconsistent methods and measurements and conflicting results.

Discussions throughout the conference illustrated the complexity of the issue. Guy Loneragran, DVM, a veterinary epidemiologist and professor of food safety and public health from Texas Tech University, and Morgan Scott, DVM, PhD, a Kansas State University E.J. Frick professor of epidemiology, provided an interesting point- counter-point discussion focusing on several key scientific papers regarding cause and effect in antibiotic resistance. For each case, one of the scientists argued in favor of the research methodology and conclusions while the other played “devil’s advocate,” pointing out flaws or weaknesses in the research.

Loneragan and Scott addressed several reports that have influenced scientific discussions of antibiotic resistance and the role of animal agriculture in recent years. These included a case in Quebec, where poultry producers were using in ovo injections of ceftiofur for disease prevention in chicks. After prevalence of ceftiofur-resistant Salmonella Heidelberg became common in poultry meat and humans, producers voluntarily stopped using the product in that way, and incidence of resistant pathogens dropped significantly. Reports concluded that suspending the preventative use of the antibiotic resulted in lower incidence of resistant pathogens on meat and in human illness. Scott played the role of advocate in this case, maintaining the evidence showed the drop in incidence of resistance corresponded with the change in practices. Loneragan, playing the “devil’s advocate” in this case, pointed out that levels of use of the antibiotic before the voluntary suspension were unknown, and that producers would not stop a practice that works without making other changes to account for it. Those changes could have played a role in resistance trends. Also, after initially dropping off, the incidence of resistant pathogens on meat began moving upward again, even before some producers began using the antibiotic again at lower rates.

Another example examined the Belgian experience, where a ban on all antibiotic use for growth promotion resulted in an increase in use for treating sick cattle, at least in the short term. Other examples focused on a series of papers on genomic and phenotypic modeling for interspecies transmission of resistant pathogens, third-generation cephalosporin-resistant E. coli and livestock-associated methicillin-resistant Staphylococcus aureus (MRSA).

The two scientists traded off, either arguing in support of the research conclusions or against. Both provided convincing and well-reasoned arguments to support their “positions,” illustrating how people with different opinions or perspectives, even those with the background to understand the research, can interpret the implications of these studies differently. If scientists can misinterpret the data, just think of what the consumer media or activist groups can do with it.  

Following the exercise, Loneragan and Scott summarized that antibiotic resistance should be taken seriously and approached with rigorous scientific discipline. Most antibiotics are derived from existing micro-organisms such as soil bacteria, and resistance has been occurring as long as there have been bacteria on the earth. Any antibiotic use selects for less-susceptible and sometimes resistant bacteria, but the selection process resistance is highly complex, as is determining cause and effect based on observational data. Over-simplification in interpreting data can lead to unintended consequences.

NIAA will provide the slide presentations and voice over from the conference over within the next two weeks on their website at animalagriculture.org. A White Paper summarizing the symposium will be released and available online around Dec. 31.


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