Science Friday on New Superbugs

As posted in this blog last week, an article was published in the ASM Journal Antimicrobial Agents and Chemotherapy on May 26 that describes the first discovery in the United States of mcr-1 gene, responsible for colistin resistance, in E. coli in a patient with a urinary tract infection. Colistin is considered an antibiotic of last resort because, while it causes kidney damage, it has been used to successfully treat infections resistant to standard treatments. This announcement was met with a flurry of reports in the media, including many with wild inaccuracies, announcing that this was the ultimate multiple drug resistant superbug, which is isn’t. The patient was successfully treated using other standard antibiotics. The significance of this finding is that a bacterial isolate containing the mcr-1 gene on a plasmid was isolated from a patient here in the US (not just in China, where a similar case was reported in an article in the Lancet in November). Because the gene is on a plasmid, it can be easily passed to other bacteria that have additional genes for antimicrobial resistance, and the concern is that this will happen in the not too distant future. Even the author of this article on antimicrobial resistance in last week’s issue of the Economist was confused about the difference between plastids and plasmids. (Plastids are organelles with double-membranes found in the cells of plants and algae and plasmids are small circular strands of DNA found in the cytoplasm of a bacterium.) Rather than posting links to the many examples of weak science journalism that last week’s news generated, instead I want recommend this week’s episode of Science Friday, where they provide (as usual) a careful and thoughtful discussion of the significance of the finding in the context of potential solutions for a post-antibiotic future. You can listen to it here. And I recommend this nice blog post called Apocalypse Pig: The Last Antibiotic Begins to Fail that explores the role that the agricultural use of colistin (to promote the growth of livestock) may have played in the evolution and dispersal of the mcr-1 gene in China.