Antibiotics are in your beef, at least if you eat at major fast food chains, according to a new report.

Among the 25 top fast food chains, most were graded “F” by U.S. PIRG, a nonprofit public interest research group.

The worst antibiotic offenders included Starbucks, Burger King, Dominoes, Pizza Hut, Arby’s and Applebee’s, among others.

Taco Bell was graded “D.” Subway and McDonald’s were both given a grade of “C.”

The only two food chains that got “A” grades on antibiotics in their beef were Panera and Chipotle.

Healthy livestock are often fed antibiotics as a prophylactic measure against illness, the report explains, which encourages the production of bacteria that can resist antibiotics.

“The overuse of antibiotics in food animal production contributes to the rise and spread of antibiotic resistant bacteria and is considered one of the world’s greatest public health threats,” the report says.

More than 700,000 people worldwide die each year from drug-resistant diseases, the WHO said in April. In the U.S., the CDC said each year “at least 2 million people get an antibiotic-resistant infection, and at least 23,000 people die.”

“The overuse of antibiotics in livestock production significantly contributes to the rise and spread of antibiotic resistance,” U.S. PIRG said.

To arrive at the grades, U.S. PIRG surveyed the top 25 fast food chains on how they sourced their meat and on corporate policies regarding use of antibiotics.

The report found that while there has been some progress in reducing the use of antibiotics in poultry, and the rankings to change when considering all kinds of meat at fast food chains.

For example, Chick-fil-A, known for its chicken sandwiches — and for a 2014 commitment to ending the use of antibiotics in its poultry — takes the top grade when looking at all meats.

But when focused on beef, while noting some “positive shifts,” U.S. PIRG said “policies among restaurant chains, but these are in the early stages of adoption for the most part.”

“The pace of progress is slow and not in line with either the urgency of the health threat posed by antibiotic resistant bacteria,” the report says.

Connecticut Media Group