The answer to why antibiotics do not work on viruses is very simple: it’s because viruses are not alive, and antibiotics target alive things. The reason why some docs prescribes antibiotics anyway lies in the fact that viral infections can progress to bacterial infections. The antibiotic is meant to head off or fight the bacterial infection. So, let’s talk about how exactly antibiotics work.
Antibiotics do one of two things: 1) they kill the bacteria (Bactericidal), or 2) they stop the bacteria from functioning normally (Bacteriostatic), as they are cells after all. This graphic which I did a LONG time ago for Scientific American shows the particular mechanism for the antibiotic Cipro, and furthermore, how the bacteria evolves to render Cipro ineffective. Basically, the mechanism of action for Cipro is that it cripples an enzyme called Gyrase, an enzyme that unwinds the DNA to allow replication to occur. If its DNA can’t be unwound, then the bacterium can’t replicate.
Now that you know the basics of why antibiotics work on bacteria, why do you think that antibiotics don’t work on viruses?
Answers and exploration, in next post.