McDonald’s – the world’s largest fast food chain – today announced that it is committing to serving chicken raised without antibiotics used in human medicine in all of their U.S. restaurants within two years.

This comes on the heels of new leadership for the company. Steve Easterbrook began as CEO of McDonald’s on Monday, and brings to the role a legacy of healthier food and environmental initiatives within the company’s United Kingdom division.

“We’re listening to our customers,” Marion Gross, senior vice president of McDonald’s North American supply chain, told Reuters. She said the company is working with its domestic chicken suppliers, including Tyson Foods Inc, to make the transition.

Today’s announcement marks a big step forward in protecting the effectiveness of medically important antibiotics for people, according to the Natural Resources Defense Council (NRDC). Jonathan Kaplan, director of NRDC’s Food and Agriculture program, says that “by the country’s largest fast food chain committing to working with their suppliers to keep these drugs out of the barns used to raise the chickens for their nuggets, salads and sandwiches, they are setting the bar for the entire fast food industry. (This) may be at a tipping point for better antibiotic stewardship in the poultry industry.”

Whenever an antibiotic is administered, scientists and public health experts worry that it can kill weaker bacteria and enable the strongest to survive and multiply. Frequent use of low-dose antibiotics, a practice used by some meat producers, can intensify that effect. This can support the development of so-called superbugs, who develop cross-resistance to critical, medically important antibiotics. According to the U.S. Centers for Disease Control and Prevention, such superbugs are linked to an estimated 23,000 human deaths and 2 million illnesses every year in the United States, and up to $20 billion in direct healthcare costs.