Many patients are used to their doctors emphasizing the importance of finishing all of their antibiotics, even if they are feeling better, to combat the rise of antibiotic resistance — now considered a serious health threat around the world.

But a group of U.K. researchers say not only is there no scientific evidence to support that medical advice, but it could be having the opposite effect doctors intend and actually contributing to the antibiotic resistance problem.

Dr. Tim Peto, an infectious disease specialist at the Oxford Biomedical Research Centre and a co-author of the analysis published in this week's BMJ (formerly called the British Medical Journal), says like most doctors, he was taught to tell his patients to take their full course of antibiotics.

"It's part of the medical school teaching, it's in national guidelines. It's embedded everywhere," Peto told CBC News on Thursday.

Dr. Tim Peto, an infectious disease specialist and co-author of an analysis on antibiotic resistance published in the BMJ, says doctors around the world have been taught to tell their patients they must take their full course of antibiotics without any scientific evidence to back that up. (CBC via Skype)

Peto said the research team's goal was to look at how to reduce antibiotic resistance by minimizing the amount of antibiotics that people take overall. Having patients take antibiotics for longer than they need to increases the overall consumption of the drugs and therefore raises the risk of resistance, their paper suggests.

"A lot of people have very clear views that they have to complete the course of their antibiotics so as to avoid developing resistance to antibiotics," Peto said. "We tried to find out where this came from, this idea, and what the evidence behind it was."

The team looked for scientific research to back up the strongly held notion, Peto said, and found nothing of substance. They believe the idea actually stemmed from the Nobel Prize acceptance speech given by Alexander Fleming, the man who discovered penicillin, in 1945.

In that speech, the BMJ paper says, "Fleming painted a vivid clinical vignette in which an imagined patient with a streptococcal throat infection who takes insufficient penicillin, transmits the infection — now in resistant form — to his wife, and is thus responsible for her subsequent death from antibiotic resistant disease."

"[That has] really gotten embedded in everybody's psyche," Peto said. "What basically we want to say is, 'let's challenge that and say we don't think it's the case.'"

Dr. Andrew Morris, director of the antimicrobial stewardship program at both Mount Sinai Hospital and University Health Network in Toronto, agrees that physicians have long been telling patients to take antibiotics for longer lengths of time "based on no scientific evidence whatsoever."

"In general we've always thought that a little bit longer is a little bit better," Morris told CBC News. "I would say the conventional thinking — certainly what's been spread around for a long time — is that if you stop your [antibiotics] course too short you're going to help breed resistance."

Toronto-based antimicrobial specialist Dr. Andrew Morris says it 'intuitively' makes sense for patients to take antibiotics for a shorter length of time, but they should have a conversation with their doctor instead of stopping taking them on their own. (CBC)

Morris also agrees that line of conventional thinking could be contributing to the very problem it's meant to prevent.

"Resistance primarily emerges when bacteria are exposed to antibiotics," he said. "So the longer bacteria are exposed to antibiotics, the greater the risk of resistance developing."

The British researchers are not the first to challenge traditional medical thinking around antibiotic resistance. In February, Canadian health reporter Helen Branswell published a story on the Boston-based health website STAT, quoting infectious disease experts in the U.S. who were advocating for doctors to change the advice they gave patients around antibiotic use.

The World Health Organization has updated its public guidelines on taking antibiotics, removing a paragraph from November 2015 that said, "by taking the full course prescribed by your doctor, even if you start to feel better earlier, you increase the chances of killing all of the bacteria and reduce the risk of resistance."

Instead, the WHO's current guidelines tell people that, "feeling better, or an improvement in symptoms, does not always mean that the infection has completely gone. Your doctor has had years of training and has access to the latest evidence – so always follow their advice."

But public health agencies in various countries, including Canada, continue to promote the message that patients must always take their full course of antibiotics. The "prevention of antibiotic resistance" page of Health Canada's website says, "even if you feel better, finish your antibiotics as directed to make sure that all of the bacteria are destroyed."

Peto wants to see those kinds of public health messages changed, but acknowledges it will take careful consideration of the wording to make sure people don't simply just stop taking their antibiotics when they feel better without consulting with a doctor first.

In turn, doctors need better science garnered through clinical trials to show exactly how much antibiotic is required to treat specific bacterial diseases, so they can confidently prescribe the lowest amount, he said.

In addition, the BMJ analysis emphasizes that some diseases have already been clinically proven to require longer courses of antibiotics — and that patients take all the medication — including tuberculosis.

The research team was comprised of nine experts in infectious diseases, microbiology, health psychology and epidemiology, plus a project manager, from British universities and hospitals.