Tuberculosis



More than 2000 years ago in ancient Greece, Hippocrates described a common illness that he called "phthisis". We believe this was the same disease that we today call tuberculosis, or TB. TB is a disease caused by a bacterial infection. It can affect many parts of your body, but is found most commonly (80% of the time) in the lungs, where it is called "pulmonary tuberculosis".

Over the centuries since Hippocrates, tuberculosis has been known as a major scourge of the human species, and of other species as well. During the first half of the 20th Century, TB was called "consumption" or "white plague", and it was the number one killer of Canadians. The historic menace of the "White Plague" continued for so many centuries because people had a poor understanding of the disease and poor medical tools with which to fight it.

Today, however, our understanding of tuberculosis together with our sophisticated medicine allows us the upper hand on this once dreaded disease. Humans have claimed a victory over tuberculosis in developed countries like Canada, thanks to medical science. The reason we can be so bold is not that this disease has disappeared, but because it can be cured!

What Causes Tuberculosis ?
Tuberculosis germs are too small to see without a microscope!
TB is caused by bacteria that belong to a special group of microorganisms called mycobacteria. The species of bacteria that most commonly infect humans is called Mycobacterium tuberculosis complex. Experts call it "MTB" for short. Canadians once developed tuberculosis from a different species also, Mycobacterium bovis. M. bovis is aare bacteria carried by cattle (called "bovine TB"), but this no longer occurs commonly in Canada. People living in other parts of the world may also develop TB from a bacteria called Mycobacteria africanum, but this type is not transmitted in Canada either.

Within this related group of germs called the mycobacteria are several other disease-causing bacteria referred to as "non-tuberculous mycobacteria". For example, the species causing leprosy (Mycobacterium leprae) belongs to this group.

Mycobacteria are long, rod-shaped cells that develop into long chains that look a bit like a string of sausage links when viewed under a microscope. Many bacteria cells are long and slender like this and are known as "bacilli". This is why the tubercle-forming TB bacteria are often called "Tubercle bacilli".

Here is what you see when you look at TB germs under a real microscope.

Unlike the cells of humans and animals, bacteria have walls around their cells, and the walls of mycobacteria are very special. They are made of 60% "mycolic acid", a special lipid substance that is only found in Mycobacteria, nowhere else. This mycolic acid makes the cells hydrophobic, or resistant to water--an effect that is much like pouring water over a surface that is covered with margarine. This property is important because it once made MTB difficult to stain for identification, and even today lab workers have to use a special technique to distinguish these bacteria.

Mycobacteria are aerobic, which means they like to grow in an environment with oxygen, and MTB like a bit of carbon dioxide as well. Mycobacteria do not like Ultraviolet (UV) rays from the sun. MTB is susceptible to inactivation from UV light and this is the reason why TB patients were once prescribed a sun tansuntan for treatment of their disease.

Like many mycobacteria, MTB is heat-sensitive. This is why the label on your milk carton will saysay, "heat pasteurized". For many years in Canada, milk producers have been required by law to heat all milk to a certain temperature for a specific length of time to kill all mycobacteria present. It is because of this pasteurization process that milk is safe to drink in Canada and other developed countries. If you are travelling to other countries, you need to make sure that any milk you drink is pasteurized or you might risk transmission of bovine tuberculosis.

How Pulmonary TB Develops

Tubercular infection typically goes through three stages in the human being:

** Note **

Please remember that the information presented in this forum is for your education only, and is not intended to extend medical advice or diagnosis. If you have questions or feel that you may be experiencing symptoms similar to those presented, please call the Berkeley County Health Department at (304) 263-5131 or your primary care provider for formal medical attention.