BRISTOL, ENGLAND - JANUARY 07:  In this photo-illustration a man holds a burger purchased from a fast food outlet on January 7, 2013 in Bristol, England.  A government-backed TV advert - made by Aardman, the creators of Wallace and Gromit - to promote healthy eating in England, is to be shown for the first time later today. England has one of the highest rates of obesity in Europe - costing the NHS 5 billion GDP each year - with currently over 60 percent of adults and a third of 10 and 11 year olds thought to be overweight or obese.  (Photo by Matt Cardy/Getty Images)
What goes into the fast food meat you eat?
01:27 - Source: CNN, Getty Images
CNN  — 

Many of our favorite fast food and restaurant chains continue to contribute to the growing threat of antibiotic resistance, according to a report released Thursday by advocacy groups.

The World Health Organization calls the development of bacteria that can’t be killed by some of our current medicines “one of the biggest threats to global health, food security, and development today.”

Fifteen of America’s favorites received an “F” for their lack of action in reducing the use of beef raised with antibiotics, including Burger King, DQ, Jack In the Box, Pizza Hut, Olive Garden, Chili’s, Sonic, Applebee’s and the pizza chains of Domino’s, Little Caesars and Pizza Hut.

Only Chipotle and Panera Bread, who were early leaders in using only antibiotic-free beef and chicken, received an “A.”

This is the fifth year that six public interest groups have graded the 25 largest US fast food chains on where they stand on antibiotics. The report, called Chain Reaction V, focuses on antibiotic use in both poultry and beef food items.

Antibiotics are routinely given to animals to keep them healthy while they fatten up for slaughter. In fact, nearly two-thirds of the medically important antibiotics sold in the US go to food animals.

When antibiotics are overused, some bacteria learn to survive, multiply, and share their resistance genes with other bacteria even if those have not been exposed. Those so-called “superbugs” enter our system when we eat undercooked meat or veggies that have been exposed to irrigation water contaminated with animal waste.

And suddenly, antibiotics that once cured our infections no longer do their job.

Despite the severity of the problem, the US lacks appropriate laws to regulate overuse of antibiotics in our food chain. Thus advocacy groups have turned to some of the largest buyers of raw beef and chicken – restaurants – and asked them to use their purchasing power to force change.

Fewer antibiotics in chicken we eat

And it works. A huge success story over the past five years is the reduction of chicken raised with antibiotics in many of our favorite restaurants, said Lena Brook, director of food campaigns for the Natural Resources Defense Council, one of the groups who sponsor the study. Others include Consumer Reports, the Milken Institute School for Public Health and the Center for Food Safety.

According to the report, 90% of the chickens raised last year received no medically important antibiotics. Compare that to 2014, when “nearly half of the nine billion broiler chickens produced in the US annually were raised on a full array of antibiotics, including medically important drugs,” the report stated.

For consumers, that means antibiotic-free chicken is served in 13 of the 25 restaurants included in the study, including such heavy hitters as Chick-fil-A, KFC, McDonald’s, Burger King, and Wendy’s.

Four more restaurants are on their way to keeping their commitment to serve antibiotic-free chicken. However, eight restaurants still have no policy in place.

The early push by Chipotle Mexican Grill and Panera Bread, followed by Chick-fil-A, McDonald’s and Subway, began a domino effect that encouraged major chicken supply companies to get on board, the report said.

“In spring of 2015 Perdue and then Tyson made a really big splash when they committed to limiting antibiotic use in their chicken suppliers and they’re two of the five largest chicken companies in the country,” Brook said. “So now we’re looking for that kind of shift in the beef industry.”

High use of antibiotics in beef

It’s only the second year that the report has focused on beef, but some progress has been made. As in past years, the only two As were awarded to Chipotle Mexican Grill and Panera Bread.

The two chains have consistently stood above the rest by making sure that the beef, poultry and pork used in their foods are raised without antibiotics.

Despite their success with chicken, most of the top burger chains and restaurants, such as Burger King, DQ and Jack in the Box, failed to take any action to reduce the use of beef raised on antibiotics in their supply chains. Others didn’t respond to the survey at all, just like last year.

Subway and McDonald’s received a “C” for making a commitment to begin the process of using antibiotic-free beef in their food items.

Having a major player like McDonald’s announcing they plan to create a comprehensive antibiotic use reduction policy is a “gamechanger,” the report said.