Bacteria are microorganisms, meaning that they are life forms. The word ‘antibiotic’ breaks down into: ‘anti’ (against) and ‘biotic’ (life). Antibiotics act to inhibit the growth of, or kill, microorganisms, preventing their spread and multiplication. The first – and still most common – antibiotics come from fungi (e.g., penicillin) and specifically fight bacteria. Before the development of antibiotics for widespread use, about 70 years ago, there was a high mortality rate from bacterial infections, such as tuberculosis, pneumonia, and sexually transmitted contagions.
Today, many forms of antibiotics exist to treat several different types of infections, including parasitic infections and some fungal infections. However, antibiotics do not work on viruses because viruses are not living organisms and so are ‘not alive’. Unlike living organisms with their own cells, viruses are segments of DNA (or RNA) that inject themselves into living cells, forcing those cells to do the work of reproducing more of the viral DNA.
This is why your physician will not prescribe an antibiotic for the common cold or flu. When we are sick, we often don’t know the full nature of the infection that is attacking our bodies. We just feel bad. This can be confusing because, for example, while a cold virus attacks our body, our immune system is working extra hard and we become vulnerable to developing other types of infections, such as pneumonia or strep throat, which are bacterial infections and usually treated with antibiotics.