Urinary Tract Infection

The definition most of us use for an antibiotic is: any substance produced by a microorganism which harms or kills another microorganism. However, antibiotics DO NOT harm viruses. The reason that physicians sometimes prescribe antibiotics when you may have a viral infection, is because of the possibility that you may also acquire a bacterial infection because you are so ill with a virus - being ill places a person at risk for certain bacterial infections that are normally handled without any problem.

The overwhelming majority of antibiotic substances are natural products that certain bacteria and fungi (molds) produce and send outside of their cells. About 90% of the antibiotics in use today, are isolated from bacteria. There are a few antibiotics, however, which are completely synthetic... that is, are made from scratch in the laboratory. These particular antibiotics are designed to inhibit some process previously identified to be completely unique to bacteria, and necessary for the bacterium to remain alive.

For a bacterium or a fungus living out in the wild, if they can make something that removes or drastically "slows-down" the competition for the available nutrients, then they'll have an advantage. So, even though these microorganisms don't have the ability to decide what to make... through mutations and other events, it is possible for them to acquire such an ability to compete.. then, it is these organisms which survive more readily within the environment.