We Know Why Bacteria Become Resistant To Antibiotics, But How Does This Actually Happen?

Bacteria have been developing resistance to antibiotics for over a billion years. from shutterstock.com

Antibiotic resistance has the potential to affect everyone. Most people would have heard about antibiotic resistance and studies show many are aware the cause of the current crisis is due to their overuse. But few know how and where the resistance occurs.

A recent study revealed 88% of people think antibiotic resistance occurs when the human body becomes resistant to antibiotics. This isn’t entirely true. The resistance can happen inside our body as it is the host environment for the bacteria; but the important distinction is that the body’s immune system doesn’t change – it’s the bacteria in our bodies that change.

What is antibiotic resistance?

The Conversation

Antibiotic resistance happens when bacteria change in a way that prevents the antibiotic from working. Changes in bacteria, known as resistance mechanisms, come in different forms and can be shared between different bacteria, spreading the problem.

Bacteria and fungi naturally use antibiotics as weapons to kill each other to compete for space and food; they have been doing this for over a billion years. This means they are used to coming into contact with antibiotics in the environment and developing and sharing antibiotic resistance mechanisms.

Most antibiotics we use today are modelled on the ones naturally created by bacteria and fungi. In the past, if the bacteria didn’t encounter the antibiotic they developed resistance for, they could lose the resistance mechanism. But now, because we are overusing antibiotics, the bacteria are encountering them all the time and therefore keeping their resistance mechanisms. Hence the crisis.

Bacteria frequently now encounter antibiotics in the environment (such as the soil) as well as in our bodies and those of animals. Antibiotic resistant bacteria mostly survive these encounters and then multiply in the same manner.

This results in an increased chance of people being infected with antibiotic resistant disease-causing bacteria, which can lead to increased complications, prolonged hospital stays and an increased risk of death.

How resistance develops and spreads

Some bacteria are naturally resistant to certain antibiotics. For instance, the antibiotic vancomycin cannot kill Escherichia coli (E. coli), while metronidazole can’t kill the whooping cough-causing Bordetella pertussis. This is why different antibiotics are prescribed for different infections.

But now, bacteria that could previously be killed by certain antibiotics are becoming resistant to them. This change can occur in two ways:

  • Genetic mutation
  • Horizontal gene transfer.

Genetic mutation is when bacterial DNA, that stores the bacteria’s information and codes for its traits, randomly changes or mutates. If this change, that could be resistance to antibiotics, helps the mutated bacteria survive and reproduce then it will thrive and outgrow the unchanged bacteria.

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