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Antimicrobial resistance is one of the biggest global threats to health, food security and development. This month, The Conversation’s experts explore how we got here and the potential solutions.

“What doesn’t kill me makes me stronger”, originally coined by Friedrich Nietzsche in 1888, is a perfect description of how bacteria develop antibiotic resistance. Contrary to a common belief, antibiotic resistance is not about your body becoming resistant to antibiotics.Resistance arises when bacteria are exposed to levels of antibiotics that don’t immediately kill them. They develop defences that prevent the same antibiotic from harming them in the future, even at higher doses.

How bacteria adapt

The ability for bacteria to adapt lies in part with their astonishing rate of reproduction. Some species, such as Escherichia coli, can replicate as quickly as every 20 minutes, depending on the environment. One bacterium can become more than 68 billion bacteria in 12 hours.

However, bacteria don’t faithfully reproduce their genetic code, and mutations can slip in every generation.While most changes are bad, sometimes they can help the bacteria grow in the presence of an antibiotic. This “new and improved” population quickly takes over. Additional mutations enable survival at even higher antibiotic concentrations.This evolution of resistance can be seen by growing bacteria on a large agar plate (a nutrient support that bacteria like to grow on) with zones of increasing antibiotic levels.

Watch how bacteria develop resistance to extremely high concentrations of antibiotics (Harvard Medical School).

Growth is halted when they first encounter the next zone, but once they have developed resistance they quickly expand until they reach the next region with more antibiotic.Bacteria in your body can easily develop resistance in a similar manner during the typical seven- to ten-day course of antibiotic treatment.

Author: Mark Blaskovich Professor, The University of Queensland