The way to prevent a cat bite from getting infected is to use a prescribed antibiotic immediately you see an infection. Speed is a critical aspect of the treatment. Strictly speaking this is not preventing an infection but reacting fast to it. This is the best advice because most cat bites don’t lead to bacterial infections. Nothing happens. The skin is broken but there is no redness and inflammation in the area of the bite. It resolves itself quickly.
But occasionally (I would say rarely) you’ll see redness and inflammation around the site of the bite and the area will become tender. The inflammation will grow in size. The cat has deposited bacteria in the skin where it grows.
The key as mentioned is to take antibiotics as soon as you see redness around the site of the bite. If you do that you’ll only need four tablets to resolve the infection in my personal experience. You may need more and your doctor will no doubt advise you to take the entire course of treatment but I don’t think you’ll need it. And antibiotics can mess up the gut bacteria which is good for digestion.
However, if you wait – and the longer you wait the more severe the problem becomes – you may, exceptionally, need a hospital stay and an intravenous drip of antibiotics.
You may have some antibiotics left over from some other illness. Use them if appropriate – you decide if it is appropriate. Use by date and type of antibiotic are factors.