Antibacterial resistance is no breaking news — it rapidly has become one of the scariest public health crises on the planet, with the potential to affect every country, race, and socioeconomic class. In most cases, the term "resistant" means a bacteria cannot be killed by the most commonly used antibiotics (think penicillin), and doctors are forced to use last line of defense drugs to take care of the problem. There have been cases overseas where a bacteria has resisted even these last-resort antibiotics, but never before had such pathogens made their way to the United States. However, the U.S. Department of Defense released a report Thursday saying that doctors have identified this dreaded superbug in a Pennsylvania woman.

The woman exhibited a rare type of E.coli infection that is resistant even to Colistin — a drug Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, said is reserved for use against “nightmare bacteria.”

The 49 year old went to a Pennsylvania clinic where a urine sample was taken and forwarded to Walter Reed National Military Medical Center. No other details about the case are available, including how she was infected. However, authorities say she had not travelled outside the U.S. within the past five months. According to Newsweek, the infection was detailed in a study appearing in Antimicrobial Agents and Chemotherapy, a journal of the American Society for Microbiology. The bug in question had first been infected with a DNA fragment called a plasmid, which carries a gene called mcr-1. The gene can then be transferred into the bacteria, conferring a resistance to colistin.

“(This) heralds the emergence of truly pan-drug resistant bacteria,” the study said. “To the best of our knowledge, this is the first report of mcr-1 in the USA.”

The CDC said it is looking for other possible cases in the clinic the patient visited, and they, along with the Pennsylvania State Health Department, have mobilized to investigate the source of the bacteria. Dr. Gail Cassell, a microbiologist and senior lecturer at Harvard Medical School, told Newsweek that the potential spread and impact of the bacteria won’t be known until experts learn how the Pennsylvania patient was infected.

“It is dangerous and we would assume it can be spread quickly, even in a hospital environment if it is not well contained,” she said, adding that people could protect themselves by thoroughly washing their hands, and any produce they plan on eating.

Every year, the U.S. sees at least 2 million people infected with drug-resistant bacteria, and about 23,000 people die from those infections, according to the CDC. Frieden warned that this may be the first case of a truly drug-resistant bacteria in the U.S., but it won’t be the last. He has cautioned doctors against the overuse of antibiotics in the past, and is now urging scientists to begin development of new drugs.

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

Source: McGann P, et al. Escherichia coli Harboring mcr-1 and blaCTX-M on a Novel IncF Plasmid: First report of 1 mcr-1 in the USA. Antimicrobial Agents and Chemotherapy. 2016.