Antibiotics and resistance

Explanation

Antibiotics can kill susceptible bacteria; some instead inhibit their growth. They are ineffective against viruses, so an antibiotic does not treat the influenza virus. Antibiotics act on structures that only bacteria have, such as the bacterial cell wall and bacterial ribosomes. Viruses have no cell wall and no ribosomes of their own: they reproduce inside host cells using the host cell's machinery, so the antibiotic has nothing in a virus to act on. This distinction depends on the pathogen causing an illness, not on whether two illnesses share a symptom such as a cough.

A bacterial population can contain bacteria that differ in susceptibility to a particular antibiotic. Resistant bacteria can survive an exposure that kills susceptible bacteria. Not all bacteria start with the same resistance, and resistance to one antibiotic does not automatically mean resistance to every antibiotic.

During exposure, resistant bacteria survive more successfully. They reproduce and pass resistance to their descendants, so the resistant proportion of the population can increase. The antibiotic does not make all bacteria choose to become resistant.

Misuse and overuse create unnecessary opportunities for this selection and can accelerate the emergence and spread of resistant bacteria. Using antibiotics for viral infections can expose other bacteria to selection without treating the virus. A common misuse is not completing the full course: stopping when symptoms go leaves the more resistant bacteria alive, and they multiply. Antibiotics should be taken as prescribed until the course is finished, never shared or used for a viral illness.