Sunday, August 26, 2007

Why are Antibiotics Useless Against the Cold and Flu?

In 1928, Sir Alexander Fleming’s discovery of penicillin ushered in a medical revolution. For the first time, a drug was available to combat ancient scourges like the bubonic plague, leprosy, and tuberculosis, which were caused by bacteria.

Below is an illustration of a bacteria.

Although penicillin was very potent, it was limited in kinds of bacteria it could kill, and therefore, what diseases it could cure. Fortunately, scientists worked hard to develop the modern assortment of powerful antibiotics that we have today.

What are antibiotics?

Antibiotics are drugs that kill microorganisms. For something to be killed, it must first be alive.

Bacteria are alive because they have the basic machinery of life contained within a cell. This machinery allows microorganisms to make energy from sugar, read and copy DNA, make proteins, and reproduce.

Antibiotics work by destroying a bacteria’s machinery of life.

By destroying this machinery, bacteria will no longer be able to live.

Did you know that the machinery inside a microorganism is similar to machinery that is inside all of our cells? The antibiotics we take are chemicals that are specifically designed to destroy bacterial machinery and not our own! The next time you have to take an antibiotic, think about all the hard work put forth by biologist and chemists to make certain that you don’t get hurt when taking this medicine.


Viruses are smaller than bacteria and come in many shapes and sizes. In general, viruses have a protein coat, called a capsid, which protects the genetic blueprint (either DNA or RNA) on the inside.

Below is a cutaway illustration of the influenza (flu) virus.

Viruses lack the machinery to make energy, read and copy DNA, make proteins, and reproduce. Therefore, viruses are not alive!

***Antibiotics cannot kill a virus because it does not have any machinery of life!***

If a virus is not alive, then how do we get sick?

Viruses are the cause of the common cold and flu (influenza). To make us sick, a virus needs to insert its genetic material inside our cells. Once the viral DNA or RNA is inside a cell, it will use our cell’s machinery to construct copies of the viruses. DNA and RNA are the universal blueprints of life so our cells are unable to distinguish the viral genetic information from our own.

The cell will keep making copies of the virus until it runs of resources while pushing out the newly made viruses. Sometimes the cell will die during this process.

The only way to destroy a virus is to take an antiviral drug or have our immune systems destroy it (a subject for later post).

Now you know why the cold and flu cannot be cure by antibiotics!

-Dr. Dave

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