May 08, 2025 Antimicrobial Resistance: A Serious Global Health Threat – Part 2

Animal agriculture underwent significant changes before and after World War II, evolving into a more intensive operation. During this transition, farming animals, primarily chickens and pigs, shifted away from pasture-based systems. Instead, these animals were confined within buildings for their entire lives.

With animals housed at high densities, producers fed them new industrial feeds that contained essential vitamins, newly discovered at the time. These vitamin discoveries enabled agricultural producers to remove animals from pastures and instead raise them on factory-produced feedstuffs, which resulted in high feed conversion ratios—the amount of meat produced per unit of feed consumed.

One key figure in identifying these essential vitamins was Dr. Thomas Jukes, who worked on animal nutrition for Lederle Laboratories, a pharmaceutical company, after World War II.

In one of Jukes’ experiments towards the end of 1948, he studied the effects of different diets on the growth of baby chicks. The chicks did not thrive on a new, less expensive animal feed that used soy meal, so he was exploring the impact of various feed supplements on their growth. At the same time, Lederle was involved in the post-WWII race to discover new antibiotics, inspired by the success of penicillin. For instance, the chief pathologist at Lederle Laboratories requested a former colleague in Missouri to collect random scoops of dirt from the University of Missouri campus. One of these samples contained a bacterial species that produced a golden yellow compound capable of killing a wide range of bacteria, even more than penicillin. This bacterium was named Streptomyces aureofaciens (meaning “gold-making”), and the new antibiotic discovered from it, the first of the tetracyclines, was named aureomycin.

After cultivating a bacterium to produce aureomycin, the leftover mash contained low levels of the antibiotic alongside various nutrients produced by the bacteria, which could potentially supplement soy meal feed. In his experiment at the end of 1948, Jukes used a feed supplemented with ground raw liver, known at the time to contain a vital animal protein factor—vitamin B12—and compared it to a feed enhanced with the leftover mash from the aureomycin production vats. To his surprise, the chicks fed the aureomycin mash grew significantly faster than those receiving the liver supplement. Further investigations revealed that the small amounts of antibiotic present in the mash were the key factor contributing to the accelerated growth of the chicks.

Lederle quickly began promoting aureomycin as a supplement for animal feed, characterizing it as a vitamin rather than a drug. Jukes’ discovery gained more attention after he presented a talk at the American Chemical Society. A New York Times reporter attending the meeting wrote a front-page article on April 10, 1950, titled “‘Wonder Drug’ Aureomycin Found to Spur Growth by 50%.” In the article, the science correspondent quoted a report from Lederle, which emphasized the discovery’s “enormous long-range significance for the survival of the human race in a world of dwindling resources and expanding populations.” The company also claimed that “no undesirable side effects have been observed.”

The use of antibiotics in animal feed has contributed to the growth of intensive animal confinement practices. According to medical historian Claas Kirchhelle, there are three key advantages to adding antibiotics to animal feed. First, antibiotics help combat pathogens. Second, their prophylactic use can stop the spread of infections among animals. Third, when given regularly in low doses, antibiotics can promote animal growth and reduce the feed needed.

However, there are also significant downsides to this practice. Antibiotic-treated feed can mask poor animal husbandry practices, residues from antibiotics in animal products can cause allergic reactions in consumers, and the widespread use of antibiotics can lead to the development of bacterial resistance.

Jukes was a passionate advocate for science and a vocal critic of anti-science arguments and their proponents. He participated in many public debates on issues such as creationism, the banning of DDT, and the risks associated with antibiotic-supplemented animal feeds. For instance, in 1973, he wrote an article discussing the implications of administering low levels of antibiotics to livestock. He argued that there was no evidence linking this practice to transferable resistance in microorganisms that could pose public health risks. However, three years later, a landmark study published by medical researcher Stuart Levy and his colleagues, as reported by the National Academy of Sciences in 2016, demonstrated a direct connection between antibiotic use on farms and the emergence of antibiotic resistance in humans.

Jukes passed away in 1999, so he did not witness the widespread emergence of antimicrobial resistance throughout the globe in the 21st century. He also missed the alerts issued by public health agencies and authorities worldwide regarding the increasing bacterial resistance to available antibiotics.

(Part 3 will address efforts to regulate antibiotic use in Europe and the USA to reduce the spread of antimicrobial resistance.)