The ultimate superbug has reached American shores.

Doctors have discovered a powerful strain of E. coli that is resistant to the antibiotic of last resort, colistin, in the urinary tract of a Pennsylvania woman who sought treatment at a military hospital.

It’s not clear how the patient, who hasn’t recently traveled out of the US, contracted the bug.

Medical experts fear the pan-resistant bacteria will easily overpower current drugs.

“It basically shows us that the end of the road isn’t very far away for antibiotics,” CDC Director Tom Frieden told the Washington Post.

With Post wires