Cooking, if adequate, destroys bacteria. If you are suspicious of fruits or vegetables, peel or boil them. Water in this country and most developed countries is safe from bacteria, although not always from other germs, because chlorination doesn't kill them all. But water elsewhere can kill you, or at least spoil a perfectly good vacation. Remember that ice is no more sanitary than the water it came from.
Some diseases are still worth quarantine.
Sexually transmitted diseases, many of which are bacterial, should also observe quarantine from intimate contact. If you have diabetes you are especially prone to infections that could cause the loss of a limb. The extra sugar in your blood helps germs grow. Diabetes reduces your blood circulation, making it harder for you to heal and fight infection, especially way out at the end of your leg. Studies have shown that meticulous foot care can prevent most amputations.