The Bureau of Investigative Journalism and The Guardian found that beef suppliers for fast food giants like McDonald's, Taco Bell and Wendy's, have been sourcing meat from U.S farms that use antibiotics.
Both organisations obtained this information from unpublished U.S government records.
The antibiotics being used are known as HP-CIAs, which The World Health Organisation has listed as a vital antibiotic to human medicine that should not be used in livestock farming. HP-CIAs are commonly used in the final line of defence in fighting off infections. If they are used in the food, the effectiveness will wear off, posing a critical problem to human health.
U.S Senator Cory Booker stated that the overuse of medically important antibiotics on factory farms is a "deadly public health threat".
"Giant agribusinesses have built a system that is dependent on the misuse of antibiotics to maximise their profits, with no regard to the serious harm they are causing".
While industrial farmers have often used antibiotics to prevent the spread of disease and allow livestock to grow quicker and larger than normal, the threat of antibiotic resistance is becoming an increasing problem for modern medicine. In the U.S, more than 2.8 million people develop antimicrobial-resistant infections every year. Implications of antibiotic resistance include longer-lasting and more complicated illness, which leads to the need for stronger and more expensive drugs.
The annual death toll from antimicrobial-resistant infections in the U.S is estimated to be 35,000 people.