A family of bacteria has become resistant to even the newest antibiotics, Centers for Disease Control and Prevention said. In many cases, these infections are impossible to treat. The agency has called the family of these antibiotic-resistant bacteria as "nightmare bacteria".

The bacteria, known as Carbapenem-Resistant Enterobacteriaceae (CRE), can kill almost half of all the people that it infects. Also, the bug can spread and help other bacteria of its kind become resistant to medication, making them superbugs as well. The bacteria usually affects people who have been hospitalized for a long period of time.

"CRE are nightmare bacteria. Our strongest antibiotics don't work and patients are left with potentially untreatable infections. Doctors, hospital leaders, and public health must work together now to implement CDC's "detect and protect" strategy and stop these infections from spreading," said CDC director Tom Frieden, M.D., in a news release from the agency.

Enterobacteriaceae are quite common, and live in our guts. Over the past few decades, some strains have got resistant to a kind of antibiotic called carbapenems, which is worrisome as this antibiotic is our last resort weapon to fight an infection. Previously, CDC has tracked down the spread of a CRE from just one hospital to many healthcare settings in as many as 42 states.

CDC's findings have been published in the Vital Signs report, where the agency has described the growth and spread of CRE in the U.S.

"We have seen in outbreak after outbreak that when facilities and regions follow CDC's prevention guidelines, CRE can be controlled and even stopped. As trusted health care providers, it is our responsibility to prevent further spread of these deadly bacteria," said Michael Bell, M.D., acting director of CDC's Division of Healthcare Quality Promotion.

CDC had earlier released a toolkit that provides more information about CRE and ways to prevent a CRE outbreak.