How do antibiotics work?

An antibiotic is a drug that fights bacteria. Antibiotics can also be called antimicrobials, but this is a broader term that includes drugs that fight bacteria or other types of microbes, such as viruses or fungi. Antibiotics do not work against viruses, such as those that cause colds and flu.

Antibiotics work in many different ways. They might kill bacteria, or merely disable them or slow down their multiplication, giving the immune system more time to clear the infection. Many antibiotics stop the bacteria from making proteins, which is essential for survival and multiplication. Others interfere with their ability to copy DNA.

Penicillin, the first antibiotic to be developed as a medicine, blocks the construction of the bacterium’s cell wall. With this important part of its structure weakened, the cell can easily rupture. Daptomycin disrupts the integrity of the cell membrane, allowing ions or small molecules to leak in and out of the cell, which can also be lethal to bacteria.

Some antibiotics, described as narrow-spectrum, are only effective against specific types of bacteria, while broad-spectrum drugs can fight a wide range.

All antibiotics will have some effect on the bacteria that normally live inside our bodies and contribute to our health, the microbiome. As a side effect, they may kill some bacteria that are good for us, and make it easier for other bacteria to take their place.

We have hundreds of antibiotics, but they fall into about 15 major classes. Many are produced naturally by certain microbes to kill others. Most were discovered between 1940 and 1960. The rate at which we have developed new ones has slowed down dramatically.

Some bacteria have evolved resistance to certain antibiotics. Antibiotic-resistant bacteria are becoming more and more common, making infections harder to treat. This problem has been made worse by the overuse of antibiotics, both in medicine and farming.

Doctors often prescribe a course of antibiotics lasting one or two weeks, and tell patients to finish the course even if they feel better. Recent research suggests that shorter courses are just as effective at killing bacteria and are less likely to fuel antibiotic resistance. Sam Wong