How do antibiotics kill viruses?

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.