Antibiotic use and antimicrobial resistance; personal experience, policies and regulatory response.
Antimicrobial compounds are a natural phenomenon in any microbiome. As an example, in the human microbiome it is estimated as many as 1011 organisms per milliliter are found in the large intestine. A healthy human microbiome, immune system and stomach acidity are the first lines of defense against any pathogenic organisms on food or in water.
In nature, antibiotic-producing gene clusters are common. It is estimated screening 10,000 common soil actinomycetes would result in identifying 2,500 that produce various antibiotics (Clardy et al. 2009). It is understandable why many bacteria naturally have and express antibiotic resistant genes. Using an antibiotic does not create antibiotic-resistant genes in and of itself. Bacteria naturally evolved to have genes that allow them to survive natural antibiotic warfare in response to competition from other bacteria and fungi.
The key to fighting antibiotic resistance is to use these tools carefully, including not overusing any one antibiotic. Any level of antibiotic use in humans or animals will select for microorganisms that are already resistant. Microorganisms can transfer resistance genes to other organisms through various mechanisms, such as plasmids.
Antibiotic use in livestock becomes an issue
Antibiotic use in animal agriculture has been of interest to me for over 40 years. My interests increased as I administered antibiotics on a family dairy and swine operation.
When I completed my PhD at Michigan State University, I accepted a position as an Area Livestock Agent for the Michigan State University Cooperative Extension Service. In this role I received training to help swine producers deal with “sick building syndrome.” We knew high death losses were an issue on some farms. Despite great veterinary care and a lot of antibiotics, nothing was slowing the suffering and death loss on these farms.
The root cause was poor building design. Improper airflow was causing pigs to become sick and die. The solution was science-based air flow systems. This opened my eyes to the motives behind using too many antibiotics. In some cases, antibiotics were being used as a virtually worthless crutch.
In 1987, I accepted an appointment as National Program Leader for Animal Science with the United States Department of Agriculture (USDA) Cooperative Extension Service in Washington, DC. In this role, I helped the USDA Food Safety and Inspection Service (FSIS) deal with a spike of violative sulfamethazine residues in market hogs. As I investigated the root cause, I realized that while raising pigs myself I was not aware sulfamethazine was to be withdrawn 15 days before harvest. I also learned that if pigs defecated outside, sulfamethazine residues in soils associated with areas that held water pigs could drink were sometimes high enough to result in violative tissue residues. These experiences reminded me of the importance of proper antibiotic use education.
This awareness motivated me to serve as the USDA representative to the Food Animal Residue Avoidance Data Bank (FARAD) (CDC NARMS 2020). To this day, FARAD continues to provide free information to veterinarians and livestock professionals to ensure antibiotics are used judiciously.
Animal rights and antibiotics
In the 1990, animal rights groups
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