Professor Dave here, let’s talk tuberculosis.
Consumption.
The King’s evil.
Scrofula.
Pott’s disease.
What do these terms have in common?
They all refer to tuberculosis.
Believe it or not, tuberculosis has inspired poets, artists, novelists, and composers over
the years.
While the term “tuberculosis” was coined by Johann Schonlein in 1834, scholars estimate
that the disease has been around for as long as three million years.
Tuberculosis, or TB, often presents like the flu, with symptoms such as chills, vomiting,
weakness, night sweats, a persistent cough, sore throat, or fever.
Literally anyone can get TB, and a cough lasting three weeks or longer is often a warning sign.
So what causes it?
TB is caused by Mycobacterium tuberculosis, a bacteria that is able to establish a lifelong
infection in a host.
These bacteria are weakly gram-positive aerobic rods.
Their cell walls are rich with lipids, making them highly resistant to detergents, antibacterial
antibiotics, and disinfectants.
M. tuberculosis enter the respiratory airways and get taken up into immune cells, where
they’re able to evade being killed by the immune system, continuing to replicate and spread.
In some cases, the bacteria can spread to lymph nodes, through the bloodstream, or to
other tissues such as bone marrow, spleen, kidneys, or even the central nervous system.
Multidrug resistant TB, which is often abbreviated to MDR-TB is a particular type of drug resistant
TB, meaning that the TB bacteria that a person is infected with are resistant to two of the
most important TB drugs, isoniazid, or INH, and rifampicin, or RMP.
The bacteria that cause TB spread through the air from person to person, through talking,
singing, or coughing.
A person can breathe in these bacteria from another person’s cough and become infected.
In fact, these bacteria can float in the air for several hours, depending on the environment.
It’s worth mentioning that TB is NOT spread by sharing food, shaking hands, kissing, or
sharing toothbrushes.
There are two types of TB conditions: latent TB and TB disease.
As we discussed in an earlier tutorial, a latent infection means that the bacteria live
in the body without making a person sick.
In the majority of people who breathe in TB and become infected, their body is able to
fight off the infection and stop it from growing.
Those with a latent infection don’t have symptoms, don’t feel sick, and most importantly,
can’t spread TB to anyone else.
However, if the bacteria become active and start multiplying in the body, that person
will go from having a latent TB infection to being sick with TB disease.
Those with TB disease typically do show symptoms and can spread TB bacteria to others.
Like with all diseases that are treated with antibiotics, it is very important that people
who have TB disease finish the full treatment of antibiotics, taking great care to use the
drugs as directed.
If they stop taking the drugs too soon because they feel better, they can very easily become
sick again, but this time, the bacteria are likely to have developed resistance to those
drugs, an example of natural selection in action.
Drug-resistant TB is much harder, and way more expensive to treat.
Multidrug resistant TB has developed largely due to misuse or mismanagement of TB drugs,
as in when the wrong treatment is prescribed, meaning the wrong dose, wrong length, or wrong
drug altogether, when patients don’t take their full course of drugs, or when the drug
supply runs out or the drugs are of poor quality.
“XDR-TB” is the abbreviation for extensively drug-resistant tuberculosis, which means resistant
to at least four of the main anti-TB drugs.
To diagnose TB, doctors use either a TB skin test, called a TST, or a TB blood test.
A positive TB skin or blood test simply means that the person has been infected with TB,
and does not specify whether the person has latent TB or TB disease.
Often, a chest x-ray or sputum sample, which means saliva, can help with diagnosis.
There is a vaccine to prevent TB disease that is used specifically in some countries to
prevent severe TB in children, though it is not generally recommended for adults.
So there’s a bit of information on tuberculosis, and an important lesson on proper antibiotic use.