Tuberculosis - causes, symptoms, diagnosis, treatment, pathology

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It’s estimated that about two billion people worldwide are infected with mycobacterium

tuberculosis, often just shortened to tuberculosis or simply ‘TB’.

Two billion is a ton of people, but even though they’re infected, that doesn’t mean all

those people have symptoms, the vast majority, about 90-95%, aren’t even aware they’re

infected.

And this is because usually the immune system can contain it such that it isn’t able to

multiply, and often remains latent, or dormant, as opposed to active, which usually causes

symptoms and can be spread to others.

If the host’s immune system becomes debilitated at some point down the road, like with AIDS

or some other illness, or as a person grows older, it can be allowed to reactivate, or

basically wake up and become very serious, especially if it spreads through the body.

Mycobacteria are an interesting bunch, they’re slender, rod-shaped, and need oxygen to survive,

in other words, they’re “strict aerobes”.

They’ve got an unusually waxy cell wall, which is mainly a result of the production

of mycolic acid.

Because of this waxy cell wall, they’re “acid-fast”, meaning that it can hold

on to a dye in spite of being exposed to alcohol, leaving it bright red colored when a Ziehl–Neelsen

stain is used.

The wall also makes them incredibly hardy, and allows them to resist weak disinfectants

and survive on dry surfaces for months at a time.

Now Mycobacterium tuberculosis is usually transmitted via inhalation, which is how they

gain entry into the lungs.

Now, we breathe in all sorts of virus and bacteria all the time, but we’ve got defenses

that take care of most of them.

For one, air that we breathe in is turbulent in the upper airways, and drives most bacteria

against mucus which is then cleared pretty quickly.