Researchers say they identified a new form of resistance “to the very last-ditch drug colistin,” reports Maryn McKenna in National Geographic. “[I]t is present in both meat animals and people, probably comes from agricultural use of that drug, can move easily among bacteria, and may already be spreading across borders.” Colistin was introduced in 1959 but was little used because it can damage kidneys. When bacteria became resistant to a class of antibiotics called carbapenems, colistin became the antibiotic of last resort.
Because it’s inexpensive, colistin also is used to help food animals gain weight more rapidly in China and in some other countries. The study, published in the journal The Lancet Infectious Diseases, says researchers found colistin-resistant bacteria in a pig on a farm near Shanghai. The scientists broadened their search and found resistant bacteria in samples of raw pork and chicken, and in 1 percent of samples of hospital patients with infectious disease, says NatGeo. The gene that creates colistin resistance “is contained on a plasmid, a small piece of DNA that is not part of a bacteria’s chromosome. Plasmids move freely around the bacterial world, hopping from one bacterium to another; in the past, they have transported resistance DNA between bacterial species.”