With painstaking effort, a group of Chicago hospitals has managed to cut by half the number of infections caused by an especially deadly type of superbug. Now U.S. health officials want that kind of campaign to go national. The White House on Friday told the U.S. Centers for Disease Control and Prevention to slash rates of infections from antibiotic-resistant bacteria by 2020 as part of a plan to prevent patient deaths and curb overuse of antibiotics administered to humans and animals. The CDC is pointing to the success of the Chicago Prevention Epicenter, one of five such CDC-funded programs nationally that coordinate research between local scientists and public health officials.