WASHINGTON -- Government officials want the nation's healthcare providers to step up efforts to halt the spread of a drug-resistant "nightmare bacteria" that attacks the bloodstream and kills up to half of patients who become infected.In the first half of 2012, nearly 200 hospitals and acute-care facilities treated at least one patient for the lethal "superbug" known as CRE, according to new data from the U.S. Centers for Disease Control and Prevention.Dr. Tom Frieden, director of the CDC, called CRE a "nightmare bacteria" because of its high mortality rate, its resistance to nearly all antibiotics and its ability to spread its drug resistance to other bacteria that otherwise would be vulnerable to vaccines.Patients receiving long-term or complex medical care in hospitals and nursing homes are at the greatest risk for CRE infection. The bug is spread mainly by unclean hands, but medical devices like ventilators and catheters increase the risk of infection, Frieden said.CRE stands for carbapenem-resistant Enterobacteriaceae, part of a family of more than 70 bacteria that live in the digestive system. A strain of the superbug killed seven patients in 2011 at the National Institutes of Health Clinical Center in Bethesda, Md., but the deaths were not disclosed until 2012.In their wake, the CDC issued recommendations for healthcare facilities to stop the spread of the bacteria, and many saw dramatic declines in CRE infections as a result, Frieden said.But many facilities haven't adopted the recommendations, and the bacteria continue to spread. If the healthcare community doesn't do a better job of containing it, experts say, it could advance beyond hospitals and nursing homes, where it has been concentrated. The fear is it could follow the pattern of another bacterial superbug, known as MRSA, which has turned up in schools, gyms and other public facilities.