As is customary before the impending death of important people drugs, WIRED has prepared an obituary for colistin—the antibiotic of last resort for curing otherwise drug-resistant superbug infections. The editors realized colistin’s days are numbered, like that so many other antibiotics before it, when bacteria resistant to colistin showed up on a Chinese pig farm. In the long-term, bacteria eventually will develop resistance to any antibiotic, but the more colistin is overused, the faster resistance will spread.


AWAITING FINAL Colistin, a toxic antibiotic used to treat only the worst drug-resistant infections, died on XX at age XX. It was a gradual death, coming after a series of XX colistin-resistant bacteria outbreaks at hospitals in XX countries. Colistin leaves distant relations among the class of antibiotics known as polymyxins, but no immediate family or friends. Indeed, the drug’s passing leaves medical professionals with few—if any—options for curing deadly multidrug-resistant infections AWAITING FINAL

XX confirmed the death, saying the cause was overuse of the antibiotic drug, the same problem that did in carbapenem, methicillin, and vancomycin.

Colistin’s rise to prominence was an improbable one. Born in 1959 to a flask of fermenting bacteria and a Japanese scientist, it nearly disappeared in the 1970s, when doctors deemed colistin too toxic. The antibiotic was a talented killer of bacteria, but also wreaked havoc on kidney cells, and in 1969, an overdose of colistin killed an otherwise healthy boy. The medical community shunned colistin for safer antibiotics. “It’s not an easy drug at all,” says Yohei Doi, an infectious disease expert at the University of Pittsburgh.

But in the early 2000s, as doctors became ever more desperate for weapons against increasingly tough bacteria, they turned to colistin again. Colistin was eager for a shot at redemption, especially given that it had a chance to one-up carbapenems, a class of newer antibiotics against which more and more bacteria were becoming resistant. When doctors encountered carbapenem-resistant infections, they had no choice but to summon colistin for one last mission. Colistin still caused kidney damage, but hey, that’s better than dying.

This whole time, though–unbeknownst to most medical workers in the West—colistin was leading a double life in China. That’s what led to its ultimate downfall.

Because colistin was so toxic, China never approved it for use in humans. So who used it? Pig farmers. Feeding pigs low doses of antibiotics fattens them—a practice common throughout the world, though usually with different antibiotics. China, the world’s largest pig producer, was the biggest consumer of the 12,000 tons of colistin used in framing each year.

In 2015, this double life caught up with colistin. Chinese microbiologists published a report in Lancet Infectious Diseases about finding bacteria resistant to the antibiotic on a pig farm and on raw meat. Colistin seemed unfazed. Scientists had in fact reported seeing colistin-resistant bacteria before, but the Chinese microbiologists’ report was different. When the resistant bacteria popped up earlier in a few places like the US, Hungary, and Greece, the gene that gave bacteria immunity against colistin lived in DNA tightly wound into chromosomes, where its hard for bacteria of different species—which is often promiscuous with genetic material—to swap.

In the pig bacteria, though, the resistance gene was on a small loop of DNA that lives outside a chromosome, called a plasmid. Bacteria pass those back and forth. “That’s hugely different,” says Joseph Dillard, a microbiologist at the University of Wisconsin, Madison. Scientists feared that the pig bacteria could meet other bacteria, swap plasmids, and create new strains of colistin-resistant bacteria.


Even worse, what if bacteria already resistant to carbapenem picked up the colistin-resistance plasmid? That fear came true, in XX. Banning the widespread of use of colistin in farming could have slowed its demise, experts say.


The ghost of carbapenem, when asked about colistin, said, “How many more antibiotics have to die before they learn their lesson?”


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A Once Powerful Antibiotic Goes the Way of All Flesh