For the first time ever, researchers have found a person in America who carries a bacteria resistant to last-resort antibiotics. This is an alarming development that the top U.S. public official says could imply “the end of the road” for antibiotics.

The resistant strain was discovered last month in the urine of a 49-year-old woman from Pennsylvania. Defense Department researchers said she carried a strain of E. coli that is resistant to the antibiotic colistin — an antibiotic of last resort for particularly dangerous types of superbugs — according to a study published Thursday in Antimicrobial Agents and Chemotherapy, a publication of the American Society for Microbiology.

The authors wrote that the discovery “heralds the emergence of a truly pan-drug-resistant bacteria.”

Superbugs such as these can kill up to 50 percent of patients who become infected. The Centers for Disease Control and Prevention has called CRE — a family of bacteria which health officials have dubbed a “nightmare bacteria”— one of the country’s most urgent public health threats, The Washington Post reported.

The CDC is working with Pennsylvania health authorities to interview the patient and her family in an effort to find out how she may have contracted the superbug.

To read more about this superbug case, click here