This is according to the second annual Chain Reaction report and scorecard, released on Tuesday by a group of consumer, environmental and health organisations. The report grades America’s top 25 restaurant chains on their policies and practices regarding antibiotics use and transparency in their meat and poultry supply chains.

Antibiotics have been in the spotlight this week as world leaders at the UN signed a pledge to tackle the problem of resistance to these drugs, which causes people to die from antibiotic-resistant infections. Part of the solution is to restrict the use of the drugs in food supply chains.

Nine of the surveyed companies, twice as many as last year, received passing grades, largely due to their transition to chicken raised without antibiotics or chicken raised without medically-important antibiotics. But the organisations behind the report said restaurant chains surveyed this year made little progress on beef or pork.

“This year's scorecard shows positive signs of change in the fast food industry,” said Sasha Stashwick, Senior Advocate for Food & Agriculture at the Natural Resources Defense Council (NRDC). “But amid the steady drumbeat of company after company acting to end routine antibiotics use in their chicken supplies, chicken giant KFC now stands out as a major laggard.”

Cameron Harsh, Senior Manager for Organic & Animal Policy, Center for Food Safety: “This year’s progress is encouraging, but companies and consumers can only move the dial so far – it is time for the US government to step up and mandate reductions in antibiotic use for the industry writ large.

"Without strong, enforceable regulations for antibiotic use in place, there is undue burden on the public to hold companies to their commitments, and to pressure the laggards in the industry to stop dragging their feet," he added.