Tuesday, September 18, 2012

The Other Side of Antimicrobial Resistance

An editorial was recently published by Bill Marler’s group entitled “Letter from the Editor: Antibiotic Resistance.”(1) For the most part, I agree with this article. However, there are a few points that I think need clarification. I will use a “point-counter point” approach, although not all of these counterpoints are arguments.

Point: “Antibiotics are integral in the treatment of many food-borne diseases, making this an important issue for the food safety community.”

Counter point: Yes, antimicrobial resistance (AMR) is a big deal. Antimicrobials are used in treating infections. However, they are not the first line of defense for treating food-borne illness, even in cases requiring hospitalization. Instead, the primary course of treatment is fluid therapy.(2) Therefore, even if we could erase AMR in food-borne pathogens, it is unlikely that there will be a significant improvement in the outcome of food-borne illness cases.

Drug-resistant infections take a staggering toll in the United States and across the globe. Just one organism, methicillin-resistant Staphylococcus aureus (MRSA), kills more Americans every year than emphysema, HIV/AIDS, Parkinson's disease, and homicide combined. Nearly 2 million Americans per year develop hospital-acquired infections (HAIs), resulting in 99,000 deaths - the vast majority of which are due to antibacterial-resistant pathogens. Two common HAIs alone (sepsis and pneumonia) killed nearly 50,000 Americans and cost the U.S. health care system more than $8 billion in 2006.
Counterpoint: The impact of AMR is staggering. Resistant infections have been a problem since the discovery of penicillin, which is the reason for the invention of multiple types of antibiotics.(3) It is also important to realize that very few of the bacteria listed in the above paragraph are related to livestock and food. In addition, several other medically important bacteria, such as Pseudomonas aeruginosa, Streptococcus pneumoniae, and Mycobacterium tuberculosis, have resistance patterns that cannot be explained from livestock antimicrobial usage.(4)

Point: “Antibiotics are becoming less and less effective, in part due to over-prescription and inappropriate use.”

Counter point: I don’t really disagree with this point but I would like to “fine tune” it a bit. As soon as an antibiotic is first used, resistance begins to develop. Bacteria evolve under the selection pressure of antibiotic exposure. It is how they survive. Inappropriate or unnecessary use means extra pressure on the bacterial population, thus increasing the speed of evolution.

To the extent that agriculture is guilty for antimicrobial resistance, we repent. It is important to note that many producer groups are making major efforts to become more prudent in antimicrobial use, just like what is being done in human medicine.

Point: “If I am reading scientists correctly, there are multiple theories for antibiotic resistance and agreement that some occurs naturally in the environment. Some of these theories involve antibiotic uses by both humans and animals.”

Counter point: Both points are correct. The ability to resist antibiotics has been around since the first microbe. Many types of antimicrobial resistance were recently discovered in four million year old dirt that had never been touched by man or beast.(5) Subsequently, any antimicrobial usage, even if appropriate, allows the resistant strains to become more prominent.

Point: “Yet, is it just me, or is antibiotics used in animal agriculture the only thing we hear about when antibiotic resistance comes up? Am I wrong to look at antibiotic resistance as a big circle with animal issues maybe involving a 25 percent slice with lots of other unknowns out there?”

Counter point: No counter argument here. You are correct! Agriculture is taking way too much of the heat for its contribution to antibiotic resistance, and all published risk assessments show this contribution to be negligible. I would venture to say the percentage is much less that 25%. One paper I published shows the average American is more likely to die from a bee sting (1 in 6 million) than to get a few extra days of diarrhea due to macrolide (a common animal antibiotic) use in livestock.(6,7)

Point: “I just have this feeling that allowing animal diseases to go untreated would not contribute to food safety.”

Counter point: Again, I agree. Failure to treat or prevent illness leads to needless animal suffering. Additionally, some new research is showing that healthy animals that have recovered from a respiratory or infectious illness are more likely to be contaminated with foodborne pathogens such a Salmonella or Campylobacter.(8,9)

Point: “Antibiotic resistance is complex issue. Help direct our coverage by suggesting people we should talk to and places we should go. Where's the cutting edge research being done? This is not just some problem on the farm we haven't solved. It's bigger, broader, and more complex. Now, please submit your answers.”

Counter point: Amen brother. There many questions that have not been addressed. If society was not so busy pushing draconian and meaningless solutions such as the PAMTA (Preservation of Antibiotics for Medical Treatment Act) or collecting usage data without good data on resistance, then resources would be available to answer many of your thoughtful questions.

1Flynn, D. 2012. Letter from the Editor: Antibiotic Resistance.

2Food Poisoning Center, Sanford, FL. 2011. What is the treatment for food poisoning?

3D’Costa, V. et al. 2011. Antibiotic Resistance is ancient. Nature 477:457-461

4Bywater, R.J., Casewell, M.W. 2000. An Assessment of the impact of antibiotic resistance in different bacterial species and of the contribution of animal sources to resistance in human infections. Journal of Antimicrobial Chemotherapy 46(4):643-645. http://jac.oxfordjournals.org/content/46/4/643.full.pdf+html

5Bhullar, K. et al. 2012. Antibiotic Resistance is Prevalent in an Isolated Cave Microbiome. PLoS One 7(4): 1-11.

6 Ropeik D. et al. (2002). RISK! A Practical Guide for Deciding What’s Really Safe and What’s Really Dangerous in the World Around You. Houghton Mifflin Company, Boston, 2002.

7 Hurd, H. S., et al. (2003). The Public Health Consequences of Macrolide Use in Food Animals: A Deterministic Risk Assessment. Journal of Food Protection, 67:5, 980-992.

8Hurd, HS, Yaegar MJ, Brudvig, JM, Taylor, DT, Wang, B. 2012. Lesion severity at processing as a predictor of Salmonella contamination of swine carcasses. American Journal of Veterinary Research 73(1):91-97.

9Hurd, HS, Brudvig, J, Dickson, J, Mirceta, J, Polovinski, M, Matthews, N, Griffith, R. 2008. Swine Health Impact on Carcass Contamination and Human Foodborne Risk. Public Health Reports. 123:343-351.

Thursday, September 13, 2012

New CAST video released, "The Direct Relationship between Animal Health and Food Safety Outcomes."

The Council of Agricultural and Science Technology recently released a video entitled, "The Direct Relationship between Animal Health and Food Safety Outcomes." The video discusses how changing factors that affect animal health (including nutrition, welfare, housing systems, and antibiotic use) can have a significant impact on public health.

This video supplements the CAST paper released earlier this year. The video can be found at the link below:

Monday, September 10, 2012

Organic versus conventional meat: is one better than the other?

Organic is no safer or better than conventional. This is the findings of a systematic review recently published by Stanford University looking at the topic of whether or not food raised organically is superior to food raised by conventional methods.(1) This publication is encouraging to see, as the authors examined hundreds of studies on the topic, not just on a few hand-picked studies. Meta analysis is a powerful objective method for analyzing a collection of conflicting evidence on a scientific topic.

Why is this organic question important? The organic market is seeing a massive increase in sales. According to the paper, the organic sales market went from $3.6 billion in 1997 to $26.7 billion in 2010.(2,3) The debate over organic food continues to heat up. The cost of organic food is usually 2 to three time more. But is it worth the extra cost?

The systematic review looked at two relevant points about how we might define “better”.

The first point is whether or not organic meat has less food-borne pathogens than conventionally raised meat. In analyzing the various studies, the authors did not find any significant difference in the amount of food-borne pathogens present. For example, in chicken 67% of organic samples were contaminated with Campylobacter versus 64% of conventional samples. Salmonella contamination was 35% for organic chicken versus 34% for conventional and E. coli contamination was 65% of organic samples versus 49% of conventional samples.(4)

The second point is whether or not there is antibiotic resistance bacteria present in organic meat, and if the amount of antibiotic resistant bacteria is lower in organic meat. All types of meat, including organic, have the potential to have antibiotic resistant bacteria.(5) While the review reported that conventionally raised chicken and pork are 33% more likely to have antibiotic resistance than organic meat, the findings weren’t statistically significant.1 This means that there is simply not enough data to prove the difference is more than chance. Also, just because meat has antibiotic resistant bacteria, does not mean that harm will necessarily result. A long chain of events must happen for human health harm to occur. First, the antibiotic resistant pathogens need to survive each processing step as well as cooking. Then the consumer needs to ingest the resistant bacteria, and have illness as a result that required antibiotic treatment. The harm would only result if all of these things happened and the bacteria did not respond to the antibiotic therapy.(6)

Bottom line, today’s modern farmer is not going to wipe out the human race. WHEW!

1Smith-Spangler, et al. 2012. Are Organic Food Safer or Healthier Than Conventional Alternatives?
Ann Intern Med 157:348-366.

2Dimitri, C. Oberholtzer L. 2009. Marketing U.S. Organic Foods: Recent Trends from Farms to Consumers. U.S. Department of Agriculture Economic Research Service, Economic Information Bulletin no. EIB-58.

3Organic Trade Association. 2010. U.S. Organic Industry values at nearly $29 billion in 2010.

4Miranda JM, et al. 2008. Antimicrobial resistance in Escherichia coli strains isolated from organic and conventional pork meat: a comparative survey. European Food Research and Technology. 226:371-5.

5Adams, J.U. 2012. Drug-Resistant Bugs found in Antibiotic-Free Meat.

6Hurd, H.S. et al. 2004. Public Health Consequences of Macrolide Use in Food Animals: A Deterministic Risk Assessment. Journal of Food Protection. 67(5):980-992.