Chlamydia is the most common sexually transmittedinfection in the world. Sexually transmitted infection. And you might recall from our conversation about gonorrhea,chlamydia often coinfects with gonorrhea, or they tend to occur together. Now there are several species of chlamydia
that exist, but when we talk about the most common STI that's responsible for the disease chlamydia, we're talking about chlamydiatrachomotuis, trachomotuis. And the way it gets this name, trachoma is the term for the eye infection that occurs with chlamydia, as we'll talk about in a minute.
Now with any sexuallytransmitted infection we have to consider the mechanism by which the infection spreads from one person to another. And that process is called transmission, and there are several ways that chlamydia is transmitted from one person to another. Sex is the most common way
and that can include oral sex, vaginal sex and anal sex. Childbirth is another important mechanism for transmission, as we'll talk about in a few minutes. And finally one of the unique ways that we can transmit chlamydia that we can't with many
other sexually transmitted infections is with direct contact. Now I want to throw abig asterisks over here. Because chlamydia can only live outside of a human host for about a few seconds to a minute. So direct contact means something like scratching
an infected organ of the body, say part of the genitalia, and then directly touching another part of the body like the eye. This doesn't count for one person touching another person directly and spreading the infection. That's very rare and unlikely to occur.
Pathophysiology of chlamydia
Pathophysiologyis the study of how a disease occurs. And so if we're talkingabout the pathophysiology of chlamydia, we're talking about how this bacterial organism hijacksthe cells of our body to multiply and cause an infection. Now the unique thingabout chlamydia is that it's not a very powerful organism that
carries a lot of its own nutrients. It relies on the nutrients ofthe host cell that it infects. Which means that chlamydiamust live inside of the host cell in order to reproduce and survive. So the way I'm gonna startoff designating chlamydia will be in green. So this initial green dotright here actually has a very fancy name.
This is referred to as an elementary body. An elementary body. Which is just a fancy way of saying it looks like a dot. So the first step ofchlamydia infecting our body is that it needs to somehow enter a cell. And the way that works isbecause of our white blood cells. So I'll draw this guy right here,
make him look rather ferocious with these red teeth right here. Now this white blood cell is similar to most cells in our bodyin that it has a nucleus. So I'll draw this nucleus up here. And this is where all thegenetic information for the cell on how to survive andmake proteins is stored. So when a white blood cellsees this elementary body,
this unusual particle thatshouldn't exist in our body, it wants to eat it. And this process by whichthis white blood cell swallows the elementary body, orany foreign particle, is referred to as phagocytosis. Phagocytosis. Where if you've heard thisterm before you might recognize that cyt just means cell and phago
is just a fancy way of saying to eat. So this cell is eatingthis elementary body. And after a nice big gulp, you'll see that the elementary body is nowcontained within this vesicle. We can also refer to it as a phagosome. A phagosome. Some just means a bodythat has been eaten, phago. And I just want to point out,