http://www.latimes.com/science/sciencenow/la-sci-antibiotic-resistance-20160711-snap-story.html

In early April, experts at a military lab outside Washington intensified their search for evidence that a dangerous new biological threat had penetrated the nation’s borders.

They didn’t have to hunt long before they found it.

On May 18, a team working at the Walter Reed Army Institute of Research here had its first look at a sample of the bacterium Escherichia coli, taken from a 49-year-old woman in Pennsylvania. She had a urinary tract infection with a disconcerting knack for surviving the assaults of antibiotic medications. Her sample was one of six from across the country delivered to the lab of microbiologist Patrick McGann.

Within hours, a preliminary analysis deepened concern at the lab. Over the next several days, more sophisticated genetic sleuthing confirmed McGann’s worst fears.

There, in the bacterium’s DNA, was a gene dubbed mcr-1. Its presence made the pathogen impervious to the venerable antibiotic colistin.