When my younger sister,
now 16, was diagnosed with TB I was shocked. I knew that for school most
students needed to get tested in order to avoid transmitting this disease to
others, however, I did not really ever think about people having this disease
dormant in them. I always figured people would get TB from an infected
individual that was previously infected and so on. However, the dormancy
of this disease in my sister caught my attention. Does it mean she was born
with it? I don’t know. But I feel like this just might be the topic I need to
look into for my term paper. So to start off, there was an interesting post I read
on m.phys.org about an article that was published on the journal Nature Genetics in which the origin of Tuberculosis was discussed.
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| [1] M. tuberculosis bacterial colonies. Image credit: Centers for Disease Control and Prevention. |
At the beginning of my
search I was not aware of the amount of deaths caused by TB but I now know that
it is one of the deadliest diseases of humans, causing 1-2 million deaths per
year mostly in developing countries. But where did it come from? An
international group of researchers led by evolutionary biologist, Sebastein
Gagneux from the Swill Tropical and Public Health Institute, found the answer to
this question after using whole-genome sequencing of 259 Mycobacterium tuberculosis strains collected from different parts
of the world. They were able to construct the genetic pedigree of this
bacterium and trace its origins back at least 70,000 years ago in Africa! The
researchers also compared the genetic evolutionary trees from mycobateria to
the ones of humans and found that both have a very close relationship because of
the high number of similarities. These similarities indicate that both human
and TB bacteria emerged and migrated out of Africa. In addition, the expansion of
human populations living in large groups of people and the changes in
lifestyles may have created a perfect environment for the transmission of the
disease. The researcher’s results also depict that TB could not have been
transmitted from domesticated animals as previously thought since, “Mycobacterium tuberculosis emerged way
long before human started domesticating animals” [1].
Additional articles I've
come across indicate the high resistance to treatment by Mycobacterium but I will
discuss some of them later. However, the discovery of the evolutionary paths of
both humans and TB after the experiments of these researchers can help possibly
determine future paths the disease might take. This in turn could aid in the
production of new disease control measures and new medication advancements for its treatment. If
you all know a little bit more about TB I would love to hear your thoughts. I
know I will still research the dormancy of TB in people and try to figure out
how it was my sister contracted this disease.
Reference:
[1] Mycobacterium tuberculosis: Our African follower for over 70,000 years. Phys Org. September, 1, 2013. http://phys.org/news/2013-09-mycobacterium-tuberculosis-african-years.html
Most of society today doesn't realize that TB is really in our own backyards. Most people believe it's just found in foreign countries and never think it could infect them or someone close to them. Your story is a good example how things that we see as rare or foreign may not really be and how its important to study these things so when they do arise, we know how to fight and prevent them. I hope by studying this you are able to find out what happened with your sister contracting the disease. TB is definitely something scary to imagine someone so close to you being affected, and I hope to learn alot from any future blogs you post as you dig into the research!
ReplyDeleteThat being said, I'd be willing to bet that the cell wall of Mycobacterium species is what primarily accounts for the resistance. It's mostly composed of waxy lipids, making it very difficult to penetrate by antibiotics, dyes (for distinguishing under a microscope), environmental factors, etc. I do wonder, though, if increased resistance may be partially due to acquired resistance genes like many other pathogenic bacteria have acquired various ways.
Every single organism on earth is evolving to survive. It is not surprising that the mycobacterium are evolving. If they are not you wouldn't see anyone affected with the disease. Evolution is an ongoing race for the survival of fittest. What I know about the disease: there are two forms active and dormant as you suggested. if it is inactive you wouldn't see any symptoms of the disease but it will just stay there and wait for the right opportunity meaning it will wait for the immunity to go down. This is most notable for old people and for people with AIDS/cancer. The test for TB is called PPD which will show positive for inactive people as well. As for your sister, she can't be born with it don't worry you have no chance of getting affected. She might go it from someone with the active form (coughed in her presence). because this bacteria love to grow in our respiratory tracts (Moist and nice environment for it). Bacterial infection is never associated with heredity but genetics could be associated with a lower than usual immune system which attracts bacteria....
ReplyDeleteThank you both for your comments. Lauren your bet about the cell wall is correct indeed to some extent. As I was looking for which article to post about first I found one that where two teams of scientists published in Nature Genetics about mutations being a great factor for resistance but I will definitely get into that one next time. Mustapha, thank you for your insight about the heredity component about this. So even the dormant type of TB is first contracted by an infected individual? Not just magically appear in your system? I know I'll find more answers as I research but knowing you're a biology major maybe your brain is full of interesting biology facts pertaining to TB :]
ReplyDeleteMustapha is right about the hereditary thing. It's just like any other bacterial disease, it's an infection and can't be inherited. Even diseases in bacterial nature that are present at birth are almost always caused by transmission from mother to child because the mother is infected, not due to genetics. Mustapha is also right by saying that TB is usually found active in immunocompromised populations.
ReplyDeleteThanks :) Im always right :P just kidding!
DeleteMy great aunt had emphysema after a lifetime of smoking. At one point, towards the later stages of the disease, she was told there was evidence of a dormant mycobacterium infection (not MTB but I think MAC). Speculation was that it was aquired at some point in her childhood, since she was around farm animals. I'm not sure if the doctors were correct in that line of thinking, but its interesting that a dormant infection could later cause complications in those compromised patients with lung disease.
ReplyDeleteIs that really true, school kids have to get a tb test for enrollment? Because if so, I never did that. I've gotten a tb test, but only because I was working in the health field. My best friend had the dormant form. She found out when she was about to start her nursing residency. The good part about it, is that the government pays for all the treatment and follow up x-rays.
ReplyDeleteAlso, I watched a documentary on Netflix about the prisons in Russia. Its ridiculous how many of the prisoners have tb. And the sad part is they can't be treated, so once they're released, they are spreading that active TB to citizens!
"Prisoners are 58 times likelier to contract tuberculosis than the average Russian citizen and are 28 times likelier to die from the disease."
http://microbewiki.kenyon.edu/index.php/Tuberculosis_in_Russian_Prisons
I know we're not in Russia.... but it's still scary!
thank you for the link Gaby. It is for sure scary because if so many prisoners over there are able to contract the disease who knows how many prisoners in the US have it as well.
ReplyDelete