Consumer groups scorched nearly every fast-food burger chain in the country for continuing to buy beef raised using antibiotics in ways that make them less effective on humans.

Only two small but up-and-coming chains, Shake Shack and BurgerFi, received A grades in an annual report card issued Wednesday by a coalition of five consumer and environmental groups.

Wendy’s received a grudging D-minus for sourcing 15% of its beef from a supplier that has reduced use of one antibiotic, tylosin. The remaining 22 top burger chains failed.

Overuse of antibiotics by both the food industry and human medicine has led to the proliferation of drug-resistant superbugs that kill 23,000 people in the U.S. and increase healthcare costs by $20 billion annually, according to the Centers for Disease Control and Prevention.

A 2007 study, for instance, showed that use of tylosin in poultry flocks left strains of campylobacter bacteria that were resistant to a human equivalent of the drug.