Doctors and scientists are warning that superbugs are on the rise, after a "disturbing" study in China found a strain of E. coli resistant to "last-resort" antibiotics.

The study, which was published in the Lancet Infectious Diseases journal, reported the findings from the routine monitoring of antibiotic resistance in farm animals in China.

In the study, researchers noted "a major increase of colistin resistance," and a strain of E. coli that could transfer this resistance to other strains.

Colistin, an antibiotic first discovered in the 1940s, is often referred to as a "last-resort" treatment, Dr. Allison McGeer, the director of infection control at Mount Sinai Hospital, told CTV's Canada AM on Wednesday.

Because of colistin's high toxicity, doctors prefer to use other treatments, she said. But when alternatives fail, doctors resort to colistin.

"(In the 1940s) it was used because we didn't have other antibiotics, but it had significant toxicity," McGeer said. "As soon as we had better antibiotics we just dropped it like a hot potato. It was gone. We didn't use it for many years."

But as more bugs became resistant to preferred treatments, doctors turned back to colistin, McGeer said.

"It's a measure of how desperate we are that we have gone back to using it because there aren't alternatives," she said.

And now, the scientists behind the Lancet study say bugs are adapting so that even colistin can't stop an infection.

"It's one more marker of how much trouble we're in," McGeer said. "We didn't think we were using it enough to be in trouble with resistance. So that's part of what makes this report so disturbing."

If colistin resistance becomes widespread, it could mean a rise in "infections that are completely not treatable." McGeer said.

This could impact life expectancy and how doctors keep patients infection-free after organ transplants, chemotherapy, and major surgical procedures, she said.

And while the world isn't necessarily headed for an "antibiotic apocalypse," McGeer said it is important for both doctors and patients to be aware of the threat of antibiotic resistance.

For doctors and scientists, McGeer stressed that research is necessary to keep antibiotics effective for longer, and to develop new antibiotics to keep up with mutating bugs.

"We're really having trouble in that area," she said. "We're going to need some pretty intensive research to catch ourselves up."

And as for patients, it's important to stay up to date with vaccines, wash your hands frequently, and ask doctors questions, McGeer said.

"If your doctor offers you antibiotics, he or she may be thinking in part that you want them," she said. "If you say to your doctor, 'You know, I know about antibiotic resistance. Do I really need to take this?' You'll get an honest answer."