Some 7.7 million pounds of antibiotics are sold to treat sick people in a single year in the U.S., based on 2011 International Monetary Fund data, McKenna reported. According to the FDA, nearly 30 million pounds were sold for use in meat-producing animals; most was given for growth promotion, not for therapeutic use, and with little oversight, she said.
The use of antibiotics in livestock dates back to the 1940s. Researchers searching for ways to make animal feed more efficient and less costly tried using the newly developed broad-spectrum antibiotic aureomycin, later to become chlortetracycline. In 1948, the researchers observed that chicks given aureomycin weighed three times as much as the others. Soon, penicillin and other antibiotics would also be used to fatten livestock and, in 1961, the Food and Drug Administration approved antibiotic use for growth promotion.
“That you can cause these animals to reliably gain weight faster on the same feed, or less feed, is something that was done incredibly quickly, so quickly in fact that there was almost no consideration of the [hazards],” said McKenna.
Antibiotics in art. Before the advent of antibiotics, in the late 19th century, scientists collected blood serum from animals to treat diphtheria, an often fatal childhood disease. This picture, drawn by Fritz Gehrke, shows serum taken from horse blood, in Marburg, Germany. The artwork is part of an NLM exhibit (see details below).
|McKenna with Dr. Jeffrey Reznick, chief of NLM’s History of Medicine Division
In the 1960s, the United Kingdom established the first government-supported committee to study antibiotic use in agriculture after people became seriously ill and some died from salmonella and E. coli poisoning linked to cattle farms. Around that time, FDA began to study the issue.
|NLM’s “From DNA to Beer: Harnessing Nature in Medicine & Industry” exhibit explores the problems and potential inherent in technologies that use microorganisms for health and commercial purposes. This image, “The Era of Antibiotics” by Robert A. Thom, was commissioned by Parke, Davis & Co., for its 1950s ad campaign, “Great Moments in Pharmacy.” See the exhibit at www.nlm.nih.gov/exhibition
Over the years, concern intensified over the potential impact of animal antibiotics on human health. Veterinarians cautioned about putting even small doses of antibiotics into animals in an uncontrolled environment, said McKenna. In fact, antibiotics used to promote growth in animals often were given at low levels over extended periods—known as sub-therapeutic dosing—creating the dangerous under-dosing scenario Fleming warned about nearly 70 years ago.
Then experimental proof started to surface that sub-therapeutic dosing of farm animals can threaten human health. In 1977, the Department of Health, Education and Welfare (later renamed the Department of Health and Human Services) responded by proposing to withdraw licenses for penicillin and tetracycline for growth promotion in animals, but the plan wasn’t implemented.
Other groups began to echo their concerns, from county health departments to the National Academy of Sciences. Despite increasing public and political pressure and further research from health organizations, “The agriculture industry, which benefits from growth-promoting antibiotics that make meat less expensive to produce, is unpersuaded by any of the research and has been unpersuaded for decades,” said McKenna.
In 2004, a curious case of resistance appeared on a farm in the Netherlands, which used more antibiotics in meat animals than any other EU country, said McKenna. A young girl tested positive for a drug-resistant staph infection (MRSA strain ST398), which unlike other MRSA strains was resistant to tetracycline. Interestingly, tetracycline wasn’t used to treat human MRSA in the Netherlands but was used routinely in pigs. That means the only place this strain could’ve developed its unique resistance pattern was in pigs, said McKenna. This case also reinforced that resistant bacteria generated by antibiotic use on farms can move off farms and infect people with no connection to farming.
In 2006, the EU banned antibiotics as growth promoters in animals. The U.S. took a different approach. In 2010, the FDA asked the veterinary pharmaceutical sector to voluntarily stop using antibiotics in animals for food production purpos es. After a follow-up, Guidance 213, issued last December, 25 of 26 U.S. pharmaceutical manufacturers told the FDA they’d comply and change their labeling.
Neither the U.S. voluntary guidance nor the EU ban addresses or regulates antibiotics given to farm animals for disease prevention and control purposes, noted McKenna. It’s also unclear whether U.S. companies will continue to comply with the FDA’s voluntary directive.
The true test will be whether we see a real decrease in antibiotic-resistant infections in animals and people. The less antibiotics are used overall, the greater the chance to help protect these drugs so they keep working to save lives across the world.