Course of antibiotics

Antimicrobial resistance

What happens when the drugs don’t work any longer?

Treatments for HIV, influenza and malaria are failing. Hospital-acquired infections are proving increasingly difficult to beat. The agents that cause them are fighting back. Even diseases that we thought we’d got the better of decades ago, like gonorrhoea and tuberculosis (TB), are making a comeback.

‘Antimicrobial resistance’ is how we refer to this upsurge in hard-to-treat infections – they’re hard to treat because the pathogens keep on evolving new ways to evade current drugs. At the same time there is a scarcity of new antimicrobial drugs in the drug development pipeline, which means that, as resistance grows, we must continue to use the working drugs we have left, and therefore risk those too becoming useless.

The overuse of antibiotics, potentially in livestock as well as in people, is thought to contribute to the quicker development of resistance. By reducing unnecessary drug use we may be able to slow the spread. For instance, antibiotics intended for treating bacterial infections are often prescribed to people with viral infections like the common cold, which do not respond to the drugs. But a 2014 study found that when doctors used on-the-spot tests to diagnose bacterial infections, they prescribed fewer antibiotics.

Another reason that resistance evolves is because not everyone who is prescribed a course of drugs actually completes it. (In fact, around half of all those who are prescribed medication to take themselves do not take it as prescribed, which includes stopping taking it altogether.) This may allow microbes to survive and mutate to produce the new strains that overcome the drugs.

Lead image:

Rob Brewer/Flickr CC BY


Further reading

About this resource

This resource was first published in ‘Epidemics’ in September 2007 and reviewed and updated in January 2015.

Microbiology, Health, infection and disease, Medicine
Education levels:
16–19, Continuing professional development