Straight From the Horse's Mouth

Duane A. Lienemann, UNL Extension Educator, Webster County February 20, 2010 Edition Last week I ended this column promising some information that counters what Katie Couric and other media reports used to associate the use of antibiotics in livestock production with antibiotic resistance in humans. There are so many contradictions, let’s start out with MRSA. While CBS and Couric wanted to pin MRSA infections on the livestock industry, she conveniently forgot to tell the public that there are actually three general categories of MRSA. First, there is no doubt that the more virulent forms of MRSA are a serious human health problem. These forms are most commonly found in healthcare settings such as hospitals, dialysis centers and long-term care facilities and are often referred to as “healthcare or hospital-acquired” strains. They can cause serious, invasive illness and even death, particularly in people with weakened immune systems. There is a second, less virulent, form of MRSA commonly found throughout the general population (25-50 percent of people) that can also be found in cats, dogs, and horses. These are typically referred to as “community-acquired” forms and are often linked to shared areas, such as locker rooms. These two forms are commonly found in humans. Then there is the third form of MRSA that is less invasive than the healthcare-associated forms, and are found more commonly in livestock and rarely in humans. MRSA is not just MRSA! This livestock form (Strain 398) does not transmit as easily between people as the other two types. It has however been found in some people who have close contact with livestock (pigs, calves, and poultry), although there is no data to indicate that these people have a higher-than-normal illness rate. This “398” strain has not been found in human disease surveillance for MRSA conducted by either the U.S. Centers for Disease Control and Prevention (CDC) or monitored hospitals. It is very unlikely that the people interviewed for the CBS story had the livestock-associated MRSA. It’s much more likely these people had the very common community-acquired strain of MRSA from being in close contact with infected people – not animals. Remember they are talking about “Methicillin-Resistant Staphylococcus Aureus”. The types of antibiotics used in modern livestock production are not associated with the development of MRSA. To my knowledge, Methicillin has never been used in food animal production in the U.S.! The drug-resistant infections referred to by CBS and the other media outcries have little, to no, relationship to any antibiotic use in animal agriculture. Once again I point out that the types of drug-resistant infections that are lethal are often associated with hospital-acquired infections – and the antibiotics used in those facilities – not from livestock or the use of antibiotics in livestock! What really got my dander up is that CBS tried to link these “antibiotic resistant antibiotics” to the meat in our food supply. Couric said in the report that “Evidence of MRSA has been found in the nation's meat supply. But it's unclear how widespread it may be, because only a small fraction is tested for MRSA.” What a load of crap that is! MRSA is not a food-borne illness, thus testing meat is unnecessary. The CDC and the European Food Safety Authority agree that the risk of MRSA from handling or eating meat is extremely low. Except to plant fear in consumers, why did she say that? I found information from Dr. Alyn M. McClure, Arizona DVM, very interesting. It points out the scientific odds of a person to have an antibiotic treatment failure due to acquiring a food-borne bacterial disease from eating or handling meat. According to the study some bacteria are naturally resistant to certain antibiotics; others acquire resistance by genetic mutation over time; and some acquire resistance after exposure to an antibiotic used in human medicine or animal production. This is what really caught my eye. He said that according to the study, the following things would have to happen: The antibiotic would have to be used in the animal; The animal would have to develop a resistant bacterial strain; The resistant strain would have to survive through food processing/handling; The resistant strain would have to survive through food preparation; The resistant strain would have to transfer to the human; The resistant strain would have to colonize; The resistant strain would have to cause a disease; and the antibiotic treatment would have to fail! Let’s put that in the Las Vegas odds category. What is the probability of a person experiencing a treatment failure due to antibiotic use in swine? Here are some risk comparisons by annual probability: Being struck by lightening 1 in 550,000; Dying from a bee sting 1 in 6 million; Dying from a dog bite 1 in 18 million; Acquiring resistant campylobacter from macrolide-treated swine resulting in treatment failure <1>The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: