World Tuberculosis Day

24 Mar

Today is World Tuberculosis Day, a day dedicated to raising awareness to one of the world’s deadliest diseases, because no holiday is complete if it doesn’t involve celebrating the misery of millions of people.
That’s why Christmas is so popular.

Tuberculosis is a disease caused by the bacteria Mycobacterium tuberculosis, which is one of those bacteria that is really awesome to talk about and really annoying to work with.
Really, really, really annoying.
Seriously, you have no idea.
It sucks.

The Disease

Despite how charming Doc Holiday made tuberculosis look, the disease is just as annoying as the bacterium. If you catch tuberculosis, treatment can take anywhere from 6 months to 2 or 3 years, depending on it’s drug resistance. Oh yeah, it’s highly drug resistant. And we only really have 8 types of drugs to treat it with (2 first line and 6 second line drugs) . Mutli-drug resistant TB (MDR-TB) is resistant to rifampicin and isoniazid, the first line of drug defense doctors use. Extensively drug-resistant TB (XDR-TB) is also resistant to three or more of the six classes of second-line drugs. Totally resistant TB was first reported in 2003, and was pretty rare. At first. Now it’s a bit more widespread.
Because it’s an annoying bastard.

Also, if the drug resistance and multi-year treatment isn’t bad enough, in the United States, you have no choice on whether or not you get treated. You HAVE to get treated, because the disease is such a danger to public health. Part of the drug resistance is due to people no continuing their treatment, which can be rigorous. And while there is a vaccine, it’s has varying degrees of effectiveness against pulmonary tuberculosis.

On top of everything else, many cultures have a huge social stigma against those who have it, even after they’ve been cured. During the treatment, they may be completely ostracized from their village and even their families who fear the disease. You can’t blame the people for wanting to protect themselves, but it also leaves the patient , leaving them with no emotional support structure and facing the shame of disease. They will often find themselves alone, and become very depressed and stop taking their treatment. It’s a problem Doctor’s Without Borders has to face every day, and has done their best to bring public attention to the multiple issues surrounding the disease with their adorably named project “TB And Me”.

Most people think that TB is a “third world problem.” But in reality, it’s everywhere. There are parts of London which have rates nearly as high as Chinese provinces. Alaska is facing a tuberculosis epidemic among their homeless and do random sweeps every few weeks. Even my father caught tuberculosis as a boy living in Colorado. It is highly contagious: a person with active TB can infect 10 to 15 people a year. It killed 1.7 million people in 2009. Over 2 billion people are infected, though not all of these cased are active. Of these 2 billion, 10% will develop an active infection during their lifetime.

The Bitchy Diva

It’s a Class III organism, which means you have to use a bunch of annoying precautions when working with it. Not only do you have to process the specimens under a biohood, you have to do it in a special room completely dedicated to working with tuberculosis, and only tuberculosis. This room separated from the rest of the lab by a series of doors and negative air pressure. You also have to wear a special mask so you don’t accidentally inhale it, since the infective dose of M. tuberculosis is fewer than 10 bacterium. And before you work with it, you have to spread bleach-soaked paper towels everywhere, so that if by chance even one bacterium falls onto the counter, it will immediately die a horrible, bleachy death.

We don’t mess around with tuberculosis. It’s not a fun and cute bacteria like E.coli. It’s a high maintenance bitchy little diva that will slowly and violently murder your lungs if it gets a chance.

Science Stuffs

Mycobacterium are a genus of Actinobacteria. There are over 70 species of Mycobacteria, but most people are familiar with M. tuberculosis and M. leprae, the causative agent of leprosy. While most clinically significant bacteria grow within 18-48 hours, Mycobacteria takes it’s time. Some species will form colonies within 7 days (termed “rapid growers,” because microbiologists have a skewed perception of time), while other may take 6 weeks or longer to grow. Maybe they like to take their time growing because they don’t want to come across as desperate. Or maybe they’re just stubborn and will grow when they’re damn well good and ready.
Either way, it’s really annoying.

One of the most significant characteristics of Mycobacterium is their cell wall, which is thicker than most other bacteria and completely stuffed with mycolic acids that give it a waxy appearance. The cell wall consists of the hydrophobic mycolate layer and a peptidoglycan layer held together by the polysaccharide arabinogalactan, which is one of those words I love watching drunk people try to pronounce.

M. tuberculosis is a bacillus and may be considered Gram-positive, but this is actually a huge misnomer. Due to the high lipid content of their unique cell wall and general stubbornness, they do not retain any portion of the Gram stain, and thus are neither truly Gram positive  or Gram negative. While they don’t truly retain crystal violet, upon staining they can appear to be weakly Gram positive, because it likes to laugh in the face of logic. Or they won’t stain at all and be referred to as “ghosts.” Again, either way, it’s really really annoying.

If only they were this cute.

A much more useful stain for this species is the Ziehl–Neelsen stain, commonly referred to as the acid-fast stain.
M. tuberculosis is acid-fast, meaning they are resistant to decolorization by acids during staining.  This is due the the lack of an outer cell membrane. It decided somewhere along the way that outer cell membranes were too mainstream, and never bothered getting one.


 M. tuberculosis is nonphotochromogenic, meaning it won’t produce a pigment in the presence or absence of light. Their colonies are buff-colored, dry, rough, and honestly rather ugly. They look like demented warts.


If growth conditions are optimal in broth cultures, M. tuberculosis will actually grow in long, rope-like strands, which we called “cording,” which is actually pretty cool. M. tuberculosis is strictly aerobic, requiring high amounts of oxygen, which is why it loves to invade your lungs.. They are nonmotile, and lack spores and capsules. In terms of biochemical identification, they are negative for catalase, including the 68 degrees Celsius catalase test which is commonly performed on Mycobacteria species. They are positive for niacin and nitrate.

M. tuberculosis was first described on 24 March 1882 by Robert Koch, a guy every biologist should recognize, if not for all his grand achievements in the field of microbiology, then at least for his dapper style.

 Note the fine beard and bow tie, which can both be used to clean microscopes. He received a Nobel Prize in 1905 for his discovery. In 1998 we sequenced it’s annoying little genome.

Doctors Without Borders have made several awesome infographic posters to help educate about TB rates:
TB-infographic-treatment
TB-effects-infographic2-final

Stop TB - In My Lifetime, World TB Day, March 24. http://www.cdc.gov/tb/events/WorldTBDay/default.htm

Click here to learn more about World TB Day!
Click here to learn more about Tuberculosis and it’s growing drug resistance.

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