It depends on the antibiotic. Most antibiotics target a specific feature of a bacterium. For example, a particular broad spectrum antibiotic may target a component in the cell wall of a bacteria. Some of the good bacteria in your body may also have this receptor and be targeted by the antibiotic. Mostly, the benefit of good bacterium is that they compete for space within your body (for example, in the intestines if you have a lot of good bacteria they may compete for space and food sources with bad bacteria that you eat and therefore lessen your chance of getting food poisoning). You could replace some of the good bacteria that are killed off by eating a probiotic such as yakult. However the good bacteria grow back quickly on their own so I wouldn't worry too much.
If antibiotics kill all bacteria in your body, then how long will it take to get all of the good bacteria back
Antibiotics don't kill all bacteria in the body.
Reply:Antibiotics destroy harmful bacterias and prevent them from proliferating(multiplying),They do not kill any other bacteria except the harmful bacteria-
Reply:Have a lot of yogurt which will help you. If you are on antibiotics for a long time, you have to take an antifungal medication too, as fungus can grow in your guts, as a result of decrease of good bacterias.
Reply:I have some really terrible things happen to my body as the result of taking antibiotics.
Generally I counteract them with capsules I get from the chemist , they are called iner health plus and they contain millions of good bacteria. I actually feel much better fro taking them with the antibiotics, and you must store them in the fridge.
Reply:a few days or so
when you are taking antibiotics, it's also a god idea to eat lots of yogurt because lactobacilli are good for you and help fill the vacuum that killing off all the normal flora causes.