Antibiotics are medicine that is made to kill microorganisms.
They are usually derived from fungi or synthesized artificially in labs. Example: Penicillin.
How Penicillin Kills Bacteria?
Penicillin is a cell wall inhibitor. It works by interfering with peptidoglycan. Peptidoglycan is an essential component of the bacterial cell wall. Thus, bacteria cannot synthesize its wall which makes them easier to be destroyed.
There are other antibiotics as well which works in the same way but they target other structures in the bacterial cell.
Why Antibiotics Does Not Kill Virus?
The virus works in a completely different way. They are dead outside the cell but can replicate by incorporating into the cell's DNA. Thus antibiotics do not have any target for viruses on which they can act.
There are new types of bacteria emerging that are becoming resistant to antibiotics. Antibiotics have a selection pressure on bacteria. Only those bacteria can survive who have enzymes that can destroy bacteria. Thus, these bacteria have a chance to replicate. Due to this the new generation of bacteria will have the genes to destroy antibiotics. This is producing new varieties of organisms on which antibiotics won't work.
Cause For Antibiotic Resistance
The cause of antibiotic resistance is the improper use of antibiotics. This is exposing bacteria to the drug which gives them the advantage to adapt to the antibiotic.
How To Prevent Antibiotic Resistance
Antibiotic resistance can be prevented by decreasing the use of drugs. It should be used only in case of need. Besides this proper drug dose should be followed. This will allow the complete removal of antibiotics from the body. Thus bacteria will not have a chance to mutate.