The United States’ first known case of a superbug that cannot be killed by a last resort-style kind of antibiotic was detailed in a report by the U.S. Department of Defense on Thursday.

Centers for Disease Control and Prevention Director, Dr. Tom Frieden, announced the case at the National Press Club in Washington.

49-year-old Pennsylvania woman showed the presence of a rare kind of E. coli infection that is resistant to antibiotics, even Colistin, which doctors sometimes use as a last resort when other antibiotics fail.

The woman went to a clinic in Pennsylvania, and a sample was forwarded to Walter Reed National Military Medical Center. Walter Reed found the bacteria in her urine. No other details were available, including how the woman became infected. She has not traveled outside the United States within the past five months.

The CDC and the Pennsylvania State Health Department mobilised immediately to investigate the case and to trace the contacts the patient may have had to see if the bacteria had spread.

The CDC also said it is looking for other potential cases in the health care facility the patient visited.

The bacteria have been identified in other infections outside the United States. Doctors saw cases in

One report suggests that this kind of infection can result in the deaths of half the patients who become infected.

Antibiotic resistance has become a growing problem in this country. The World Health Organization has warned that it is one of the biggest threats to global health today.

Frieden warned that although this is the first case in the United States, we should expect to see more such superbugs in the near future. Frieden, who often warns doctors against overuse of antibiotics, urged scientists to develop new drugs quickly.

Each year in the United States, at least 2 million people become infected with other kinds of bacteria that can’t be beaten with most antibiotics, and at least 23,000 people die each year as a result of those infections, according to the CDC.

“The medicine cabinet is empty for some patients,” Frieden said. “It is the end of the road unless we act urgently.” (CNN)

•Photo shows CDC Director, Dr. Tom Frieden.