Evolution of Superbugs: Treating Anti-biotic Resistant Infections

The effectiveness of coliston, a drug of last resort in treating anti-biotic resistant infections, is threatened by new strains of E. coli, that are beginning to turn up in the United States.  Originally identified in hogs on a Chinese farm, the resistant strain has turned up in 30 countries.  Tom Philpott, in a recent article in "Mother Jones," discusses a new paper that asserts that the microbes have been in the US for at least two years.  The new strain is also resistant to carbapenems, a class of antibiotics also used to fight anti-biotic resistant microbes.  The new strain is particularly dangerous because its anti-biotic resistance moves quite readily between species by means of DNA fragments called plasmids.  The propagation of resistant microbes has been much accelerated by the use of anti-biotics in animal feed.  FDA figures show that 80% of anti-biotic production in the US goes to animal feed. Philpott notes an "Atlantic" article by Mary McKenna that showed that human UTI infections are increasingly linked to resistant microbes from poultry products.  The US poultry industry is beginning to cut down on the use of anti-biotics in feed and has never used coliston.  In China anti-biotic use including coliston is on the increase.


Coliston whose structure is shown below was discovered in the 50s and shelved because of side effects. As is evident from the structure the molecule is a cyclic pseudo peptide that must be injected.

The side effects seem to be temporary, and the severity of the threat of infection by resistant strains justifies the use of an injected drug and the risk of the side effects.  As always, the use of chemistry in medicine requires carefully controlled study and balance.  But without it we would be we would have limited defenses against communicable diseases.