system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do antibiotics work?

How does one antibiotic kill different versions of bacterial infection? And if so, why can't it kill ALL bacterial infection? And why can't it work on a virus?
gpt
They destroy or weaken various parts of how bacteria work.

For example, penicillin infiltrates the cell wall of bacteria and weakens the structure. This causes the bacteria to die.

Other antibiotics block bacterial replication or other cell functions. The key is to have one that blocks bacteria from growing while being inert to human cells.