How do antibiotics prevent bacteria and viruses?

There are several different mechanisms by which antibiotics kill or prevent the proliferation of bacteria.

For instance, penicillins and cephalosporins bind to specific sites in the bacterial cell wall and prevent the bacterium from making new cell wall, so the wall they have breaks down and the cell dies.

Others, like aminoglycosides, prevent the production of proteins in bacteria, so they cannot reproduce or grow.

Some, like fluoroquinolones bind to a protein that prevents the bacterium from being able to duplicate its DNA.

For as many different antibiotics, there are different mechanisms of action. Some kill the bacteria directly, and are called bactericidal and others prevent the bacteria from spreading and are called bacteriOStatic. BacteriOStatic antibiotics slow the growth of the bacteria and allow the immune system to kill it off.