In a talk about her most recent bestseller “Big Chicken: The Incredible Story of How Antibiotics Created Modern Agriculture and Changed the Way the World Eats,” Maryn McKenna told the story of how feeding antibiotics to poultry and other meat animals has caused greater antibiotic resistance in human consumers and consequently, increased public health concerns.

McKenna is an independent science journalist and a Senior Fellow at the Schuster Institute for Investigative Journalism, located in the Brandeis library. She has written for a variety of publications and has given a TED talk on antibiotic resistance that has more than 1.5 million views and has been translated into nine languages. She presented on bacterial resistance and her book in Rapaporte Treasure Hall on Feb. 26 with the Schuster Institute’s Founding Director, Florence Graces, moderating the discussion. After a presentation on McKenna’s work, she took questions from the audience and held a book signing.

McKenna described the history of antibiotics in farming. She began in 1948 when scientist Thomas Jukes discovered that feeding chicks small doses of the antibiotic aureomycin would cause them to gain twice as much weight as normal chicks. This was termed “growth promotion,” and lead to the widespread use of antibiotics on chicken farms.

Widespread use of antibiotics can be cause for concern with regard to public health, said McKenna. “On a global average…at least twice as much antibiotics are going into livestock as they are going into people,” she said, and every time an antibiotic is used, “we are taking a risk that disease bacteria will adapt to the drug and become resistant.”

McKenna emphasized the importance of recognizing that healthy chicks and not sick chicks were being fed antibiotics. When using antibiotics, she said, “we’re balancing the risk of resistance against the benefit of curing an infection.” If antibiotics are given to an animal that is not sick, however, “we shift the balance almost entirely over to risk.”

In an example of the consequences of widespread antibiotic use, McKenna explained how the first drug-resistant bacteria, penicillin resistant staph, emerged in 1947 and caused outbreaks in British hospitals, then Australian hospitals and finally American hospitals. Resistance had arrived in the world of medicine, but as McKenna observed, “no one seemed to consider that it might happen in farming, too.”

The problem manifested itself first in dairy farms where children who drank milk from penicillin-fed cows developed penicillin allergies from overexposure, said McKenna. As drug resistant foodborne illnesses continued to spread, the United Kingdom, in 1971, became the first government to restrict farm antibiotics.

There is researching pointing to the dangers of antibiotic feeding, said McKenna, including an experiment conducted by American scientist Stuart Levy, which, in 1976, demonstrated that resistant bacteria was moving from meat into kitchens, homes and people. It also showed that bacteria could travel through animal manure and get into the atmosphere.

McKenna then focused on the modern day use of antibiotic feeding, suggesting that Americans didn’t take the issue of resistance very seriously because “we always assumed that however bad resistance might get, there would always be another drug to fix it.” McKenna was clear that the issue is serious. She asserted that pharma companies have mostly backed off antibiotic production since 2004, reluctant to spend 10-15 years getting a new drug on the market when “bacteria birth a new generation every twenty minutes.”

McKenna warned that a “post-antibiotic world’ would mean loss of what most consider to be modern medicine like surgery or stents. Antibiotic resistance would most immediately endanger the most vulnerable patients like those with cancer, HIV or a transplant. Even a slightly weak immune system suddenly could become life threatening.

While McKenna admitted that large scale protein production and antibiotic use are growing around the world (especially in developing countries), she believed that ultimately, the “narrative arc of the story turns toward the positive.” In 2014, the poultry producer Purdue announced they would be going antibiotic free, and they did so without losing any profits. Many other poultry companies and popular fast food chain restaurants followed suit.

McKenna attributes the unusual compliance of these meat producers to ditch antibiotics to “consumer pressure.” According to McKenna, school systems, health care systems, families, and farmers overwhelming communicated such a strong desire for antibiotic free meat that large companies could safely make this change knowing that “there would be a market waiting for them on the other side.”

McKenna concluded with the heartening image of the public actively advocating for the conditions of their consumption, but also cautioned that the antibiotic resistance movement will always exist as a problem, and increasingly as a global one.

The event was sponsored by the Schuster Institute for Investigative Journalism, the Environmental Studies Program and a variety of other student and administration groups at Brandeis.