WASHINGTON — Government officials want the nation’s health care 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.

“It’s not often that our scientists come to me to say that we have a very serious problem and we need to sound an alarm. But that’s exactly what we’re doing today,” Frieden said Tuesday in a telephone press briefing.

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 because they allow the bacteria to get deep into a patient’s body, 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 health care 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 health care 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.

“Compliance with hand-washing, with using gowns and gloves properly, remains a challenge, and it’s something that we call on health care facilities to work with their providers” to do a better job of, said Arjun Srinivasan, the CDC’s associate director for hospital-associated infection prevention programs. “We have the weapons at our disposal right now to stop this from becoming a bigger problem.”

Nancy Foster, vice president of quality and patient safety policy at the American Hospital Association, said hospital testing should be a facility’s decision, based on the prevalence and risk of CRE in the area. The added cost of testing and the protocol that comes with it is often an expense that many hospitals would struggle to fund, but Foster said the AHA supports hospitals looking for creative ways to finance those efforts.

Over the last decade, the proportion of Enterobacteriaceae bacteria that is resistant to carbapenem antibiotics has grown from 1 percent to 4 percent, while the prevalence of the most common CRE has grown from 2 percent to 10 percent.

“That’s a very troubling increase,” Frieden said. “The good news is that we still have time to stop CRE. Many facilities can act now to prevent CRE from emerging, or if it has emerged, to control it.”

He called on health care facilities to adopt a “detect and protect” strategy. Among the steps: increasing patient testing, including incoming and transferring patients, and requiring immediate notification of results; following special hygiene guidelines when dealing with CRE-infected patients; and dedicating rooms, staff and equipment for CRE patients.

Another step would be removing medical devices, like catheters, as quickly as possible to avoid infection, and prescribing antibiotics more carefully to avoid overuse, which increases drug-resistant infections.

Betsy McCaughey, chairman and founder of the Committee to Reduce Infection Deaths, a patient advocacy group, said Frieden’s recommendations were disappointing and “half-baked” because they didn’t call for universal mandatory CRE screenings at hospitals and public reporting of the data.

“Any patient planning to go to in a hospital has a right to know if there are germs in that hospital,” McCaughey said.

Only six states – Tennessee, Oregon, Minnesota, Colorado, Wisconsin and North Dakota – require reporting of CRE infections in hospitals, Frieden said, adding that the CDC supports those measures.