E. coli bacteria carrying the mcr-1 gene was found in a urine sample from a Pennsylvania woman with no recent travel outside of the U.S. The mcr-1 gene makes bacteria resistant to the antibiotic colistin, which is used as a last-resort drug to treat patients with multi-drug-resistant infections, including carbapenem-resistant Enterobacteriaceae (CRE). The mcr-1 gene exists on a plasmid, a small piece of DNA that is capable of moving from one bacterium to another, spreading antibiotic resistance among bacterial species. The CDC and federal partners have been hunting for this gene in the U.S. ever since its emergence in China in 2015. Read the complete CDC news release here.