Physicians are concerned about the agricultural practice of giving antibiotics to healthy animals for growth promotion and disease prevention, according to a poll conducted by the Consumer Reports National Research Center poll. The national poll, conducted last month, questioned 500 family practice and internal medicine physicians and found that 93 percent said they are concerned about animal antibiotic use. Eighty-five percent of the doctors said they had treated a patient with a suspected or confirmed case of an antibiotic-resistant infection within the past year. “This poll underscores how important it is to preserve the effectiveness of antibiotics,” said Jean Halloran, director of Food Policy Initiatives at Consumers Union, the policy and advocacy arm of Consumer Reports. “We’re calling on supermarket chains — which have huge leverage with meat producers — to help end the overuse of antibiotics in livestock.” On Thursday, Consumers Union also delivered a letter signed by 2,000 medical professionals to Trader Joe’s headquarters in California asking that the grocery chain only sell meat from animals raised without sub-therapeutic antibiotics.