A "nightmare bacteria" that became increasingly resistant to strong antibiotics and killing half of the patients infected surfaced in nearly 200 U.S. hospitals according to public health officials on Tuesday.

The Centers for Disease Control and Prevention called the new bacteria CRE which stands for Carbapenem-Resistant Enterobacteriaceae.

"Our strongest antibiotics don't work and patients are left with potentially untreatable infections," Dr. Tom Frieden, director of the Centers for Disease Control and Prevention, said in a statement before an afternoon news conference.

"These are nightmare bacteria that present a triple threat," he said. "They're resistant to nearly all antibiotics. They have high mortality rates, killing half of people with serious infections. And they can spread their resistance to other bacteria."

CDC stated it has been mostly found in hospitals and nursing homes and not in the community at-large.

About 4 percent of hospitals and 18 percent of nursing homes have treated at least one patient with the infection, within the first six months of 2012.

"The good news," Frieden added at an afternoon teleconference, "is we now have an opportunity to prevent its further spread." But, he continued, "We only have a limited window of opportunity to stop this infection from spreading to the community and spreading to more organisms."

CDC said with proper precautions and better practice can control the spread of germs.

"Doctors, hospital leaders and public health [officials] must work together now to implement the CDC's 'detect and protect' strategy and stop these infections from spreading," Frieden said.