- [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.