Zoom in on microorganisms

Reinforcements for our defense system

© Barbara Bélanger, Armand-Frappier Museum


Do you know why you can only catch chicken pox once in your lifetime? Actually, it is possible for the chicken pox virus to re-infect a person who has already had the disease…But his immune system will recognize and eliminate the virus so rapidly that the symptoms of the disease will never be felt. Vaccine production uses this principle to our advantage.

The goal of a vaccine is to show our body what the harmful microorganism looks like without, however, giving it the disease. To do this, we inject a healthy person with living weakened microorganisms, dead microorganisms, microorganisms that resemble the harmful microorganism, or fragments of microorganisms. The body will recognize the strange molecules and will eliminate them without getting infected. A very important step in this elimination is the production of memory cells that will remember the intrusive molecules. Later, if the real microorganism appears, the body will recognize it immediately thanks to these memory cells. This is how the body avoids disease!

Vaccines may be used against all types of harmful microorganisms, including viruses and bacteria. Some examples are the influenza vaccine (caused by the influenza virus), the one against hepatitis B (also caused by a virus) or the one against meningococcus (caused by a bacteria responsible for meningitis).

Antibiotic treatment on bacteriaZoomZoom
© Dennis Kunkel Microscopy, Inc.


Antibiotics are molecules produced by microorganisms to defend themselves against other microorganisms. We have simply used these antibiotics to increase our protection against microbes. It should be specified that antibiotics are only effective against bacteria (such as the bacteria that cause tuberculosis, salmonellosis and pneumonia). Viruses are not at all affected by antibiotics. There are, however, some anti-viral agents that can be used to treat viral infections such as those caused by the herpes or HIV viruses. Moreover, antifungal and antipaludism treatments are available to fight diseases caused respectively by fungi or parasites such as those that causes malaria.