After two confirmed U.S. cases of a superbug that thwarts a last-resort antibiotic, infectious disease experts say they expect more cases in coming months because the bacterial gene behind it is likely far more widespread than previously believed. Army scientists in May reported finding E. coli bacteria that harbor a gene which renders the antibiotic colistin useless.

The gene, called mcr-1, was found in a urine sample of a Pennsylvania woman being treated for a urinary tract infection. On Monday, researchers confirmed preliminary findings that E. coli carrying the same mcr-1 gene were found in a stored bacterial sample of a New York patient who had been treated for an infection last year, as well as in patient samples from nine other countries. FULL REPORT