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Video transcript

- [Voiceover] Shigellosis is often caused by many bacteria of the Shigella genus. One of the most common bacteria that causes it is Shigella dysenteriae. Another bacteria that can cause it is called Enterohemorrhagic E. coli. Now, these are just fancy names to refer to different types of bacteria. But in general, both of them produce a toxin known as the Shiga toxin, named after the Japanese scientist who discovered them, Kiyoshi Shiga. People usually contract the infection when they eat some kind of contaminated food or water. And it's usually contaminated with feces. Now, when you eat all this stuff, the bacteria will first enter your stomach. Ordinarily the stomach has a very acidic environment. But these bacteria are very sturdy. They can actually survive past the acidic environment of the stomach. In addition to this, you only need about one to 10 organisms to cause an infection. So it's very infectious. Now, once it makes its way past the stomach, it'll enter the small intestine. And then after that, it'll enter the large intestine, otherwise known as the colon. And this is mostly just responsible for absorbing water. So you have a whole bunch of epithelial cells that line the large intestine that will be absorbing water. So here is one such epithelial cell. The bacteria will have the Shiga toxin associated with its cell wall. That Shiga toxin will then be able to enter the epithelial cell of the large intestine. Now, in all your karyotic cells in the human body you have these organelles called ribosomes. Ribosomes are responsible for synthesizing proteins. But the Shiga toxin will actually stop them from doing that. So the ribosomes are no longer able to produce any proteins. Because you don't have any ribosomes producing proteins, this epithelial cell will then subsequently die off. So now you don't have these epithelial cells available to absorb all that water. So you can imagine the different kinds of symptoms associated with this. First, you may start to see a whole bunch of ulcers that form on the wall of the large intestine. People may also experience some bloody diarrhea. There may also be some rectal bleeding and some cramps due to the inability to absorb water. People may also experience tenesmus, which is really just the consistent sensation that you need to evacuate your bowels even when your bowels are empty. Now, usually these are the symptoms associated when the bacteria is in your gut. But sometimes it can actually enter your bloodstream. And those are often rare cases. But when it does, you can experience a fever. And if it gets really, really bad, you can also get some seizures. Now, all in all, these are some of the major symptoms associated with Shigellosis. But there are also a number of other possible complications that you may experience. These complications usually arise in your kidney. So I actually want to zoom in on a very small portion of the kidney. And this structure is gonna be responsible for filtration. Here we have some blood vessels, right. So blood may enter through here. And then it'll actually exit through here. And then you'll see this bundle of capillaries here known as the glomerulus. This glomerulus is actually encompassed by a structure known as the Bowman's capsule. Stuff in the blood will be filtered from these blood vessels into the Bowman's capsule. This will form what's called the glomerular filtrate. That filtrate will then go through further processing to ultimately become urine. Now, these capillaries actually have these cells that line them called endothelial cells. These endothelial cells may have receptors for the Shiga toxin. So maybe the Shiga toxin comes along and binds to these receptors. And when this happens, the immune system may come along and actually notice that these cells are infected with the Shiga toxin. Then through a mechanism that's actually a little bit understood this will lead to the formation of a clot. And that clot is really just going to prevent blood flow through this area. When this happens, you can imagine that there will be a lot of symptoms associated with the kidneys. So for example, there may be total kidney failure. In other cases people may see decreased urine output. And they may also see blood in their urine. This overall condition is known as hemolytic uremic syndrome. And maybe you wanna go to the doctor to really confirm that you have this particular bacteria. In doing so, the doctor will order a stool sample which will then be sent off to a lab to see if the bacteria is in that sample. Now, if you want to treat Shigellosis, the best thing to do is to just drink a lot of fluids. And that's just because your large intestine isn't really able to absorb the water as well. But usually medicines aren't really prescribed because the symptoms kind of go away after about one week. However, if it is very severe, then the doctor can prescribe you antibiotics. Of course, you have to be very careful when taking these antibiotics because you also have some good bacteria in your gastrointestinal system that are helping you digest all the food and water that you consume. And of course, like always, the best way to prevent getting this in general is to eat clean food and drink clean water.