In the news this week is the story that an antibiotic of last resort for curing otherwise drug-resistant superbug infections has succumbed to a resistant bacterial strain in China. The unfortunate discovery has led to a widespread call by scientists for urgent restrictions on the use of the class of anti-biotics called polymyxins, which includes colistin.

According to Reuters (LINK) “A new gene that makes bacteria highly resistant to a last-resort class of antibiotics has been found in people and pigs in China – including in samples of bacteria with epidemic potential, researchers said on Wednesday.” They go on to note that “China is one of the world’s largest users and producers of colistin for agriculture and veterinary use.”

The lead researcher team that discovered the findings, suggests “the progression from extensive drug resistance to pandrug resistance is inevitable, (And) although currently confined to China, mcr-1 is likely to emulate other resistance genes … and spread worldwide.”

Wired Magazine wrote an ‘autopsy’ of colistin, and notes that colistin has an interesting history:

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.

Here is the link to the wired story: