Why are antibiotics becoming less and less effective?

Bacteria are living organisms that evolve. Every time you use an antibiotic, susceptible bacteria die, but random mutants that can resist the drug survive and multiply. Excessive and improper use of antibiotics, both in humans and in animals in livestock farming, greatly accelerates this process. Resistant strains such as MRSA (a variant of the well-known skin bacterium Staphylococcus aureus that is resistant to many drugs at once) have by now spread worldwide.

Also dangerous is the fact that bacteria can pass resistance on to one another, even to entirely different species. They exchange small pieces of DNA that carry the resistance genes. This is the most common mechanism of spread. In this way, a harmless gut bacterium can receive resistance genes from a disease-causing bacterium and later pass them on again.

Bacteria have several tricks to outsmart antibiotics. They can actively pump the drug out of the cell before it causes damage. They can make their cell wall less permeable, so that the antibiotic does not even get inside. And some bacteria, such as the stomach bacterium Helicobacter pylori and the feared Pseudomonas (which is dangerous for people with a weakened immune system), produce enzymes that chemically break down antibiotics before they can work. Even the most powerful 'last-resort drugs' are rendered ineffective as a result.

On top of that, bacteria sometimes cluster together in a protective layer of slime, known as a biofilm, on wound surfaces or on implants. Antibiotics barely penetrate that layer. A small proportion of bacteria can also switch to a kind of dormant state: they stop dividing, and because antibiotics act precisely on actively dividing bacteria, these 'sleeping' cells survive the course of treatment. As soon as treatment stops, they become active again.

The resistance genes also do not stay neatly within hospital walls. They have been found in wastewater, in migratory birds, and even in remote ocean areas. At the same time, courses of antibiotics also damage the beneficial gut bacteria, making it easier for resistant bacteria to claim a foothold in your own body. Resistance is therefore not a problem confined to sick people or livestock farms, but a global, irreversible process that spreads along many routes simultaneously.