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What is chancroid?

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Raja Narayan.

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Video transcript

- [Voiceover] Chancroid is a sexually transmitted infection that's caused by the bacterium haemophilus ducreyi, heaemophilus ducreyi, and it's a bug that's found mainly in tropical settings. Now because chancroid is a sexually transmitted infection, it is transmitted or spread from one person through another so transmission through sex. And that can include vaginal sex, anal sex or oral sex. Now if we talk about all the different signs and symptoms a person will get with chancroid, now this is our friend here, this poor patient that's going to have all the different signs and symptoms, one of the first things you'll see are these strange, light to dark green shears in excrement. And the reason that happens is I'll kinda show right up here, I'll draw this dot to represent the haemophilus ducreyi bacterium. The reason why this happens is because the chancroid bacteria is fighting white blood cells, and as a result of this struggle or this combat, we will get inflammation, which can lead to fever or other symptoms I'm going to mention here. So let's say through anal sex, we have the chancroid bacteria spread here, through the anus into the rectum, and this is actually a sagittal view of a woman, so if you imagine you chop them in half, between the eyes, down the nose, and one leg in each piece, this is the inside of one piece, and you can see through the anus and into the rectum that we have these chancroid bacteria spreading up here where they're going to fight white blood cells, and they'll be shed in the excrement that we have for here. But you can also have the chancroid spread up the urethra. So this goes up to the bladder. And let me label this the urethra, or you can even have the chancroid bacteria spread up the vagina to the cervix. So I'll label this as the cervix. So from the spread of chancroid up the urethra, you'll get this infection of the urethra, known as urethritis. This can cause painful urination, also known as dysuria, dys-uria. Or let's say if it goes and irritates the cervix, inflammation there is called cervicitis, cervicitis. And if this infected woman is having sex, she may have pain associated with intercourse, and that's referred to as dyspareunia, dyspareunia, so pain during sex. Now nearby the genital tract, chancroid can also spread to the lymph nodes that are lining around here. And these are called the inguinal lymph nodes. I'm drawing them right now, but what can happen is that when they spread to these lymph nodes, you can get enlargement there, because this is where the white blood cells will fight the chancroid bacteria. This is referred to as lymphadenopothy. So lymphadenopothy, or swollen lymph nodes, and specifically, this is inguinal lymphadenopothy because we're having this happen in the inguinal lymph nodes, but you can just as well have axilliary lymphadenopothy in the axilliary lymph nodes. But one of the things that you can have happen if these lymph nodes become too big, and they're not really able to contain all that inflammation from the chancroid fighting the white blood cells, they can actually pop internally, and you can have rupture. And when that happens, you can get an infection deep within where the lymph node was, and these are referred to as buboes, buboes. And actually I've got a picture of a bubo here, and I think you can appreciate how swollen these inguinal lymph nodes are in this gentleman in the picture. Now the last symptom I'll mention for chancroid that's actually the most characteristic, is what's referred to as a painful chancre, a painful chancre, which may be a term you've heard before. A painful chancre, which I'll draw right here, and you'll see that it's just this indurated lesion that happens on mucous membranes. It can happen on the tip of the penis, or even on the walls of the vagina, or most commonly, in women, on the cervix. This chancre is indurated, so I'm gonna draw the walls here, implying that they're raised. So it's an indurated lesion that's happening here on the tip of the penis. And what makes this most unique, is that it's painful, because we often talk about a chancre in syphillis, where it's characteristic to have a painless chancre. So a painless chancre. And the way I remember this, because syphillis is caused by treponema pallidum, whereas chancroid is caused by haemophilus ducreyi. If you have chancroid, you do cry. Because that chancre is pretty painful. The other interesting thing about these painful chancres, or these ulcers, is that women will tend to have a lot more of them. So on average women will have four or more ulcers, whereas men, on average, only have one. Now moving on, diagnosis of chancroid. So how do we diagnose chancroid? Well there are three main tests that are used. The first is a classic gram stain. And what you'll see under the microscope, if you've got chancroid, are gram negative, so gram negative coccobacilli. So gram negative bacteria in a gram stain will usually turn up red or saffron, so I'll just write "red" here. And something that's coccobacilli, these are two different shapes that are mentioned, which means cocco, referring to round or spherical, and bacilli, referring to rod-like. The other test we can do is a culture. A culture, or we can grow the chancroid bacteria on this petri dish. And we do that by swabbing a sample from someone we suspect the infection in here, and we let that grow for usually, something like five days. Then, what you'll see are colonies of chancroid, or the haemophilus ducreyi bacteria growing here. Finally, the last test that you can do is a polymerase chain reaction test, or a PCR, which we use to detect the haemophilus ducreyi nucleic acid, or the DNA. And this test is usually preferred if able to do it, because it's the fastest of the three I've mentioned here. Okay, so let's say we've diagnosed chancroid. Now, how do we treat it? Well, like all sexually transmitted infections caused by bacteria, the treatment here will be antibiotics, and we can in fact use the culture to determine what antibiotic the bacteria are sensitive to. So we use the culture to determine sensitivity. And what that just means is that when we do this culture test, we can put a little bit of this antibiotic here, to see how the haemophilus ducreyi will grow in response to it. And maybe we'll also put another antibiotic up there, to compare. So over time, we'll see that the haemophilus ducreyi grew up here, where we had this type of antibiotic, maybe antibiotic two, we'll call it, whereas antibiotic one, that we smeared down here, had no growth of the chancroid bacteria around it, which means this will be the antibiotic of choice for us to treat the infection. Now finally, let's skip back here and ask the question about how can we prevent chancroid? Well, the trick here, like most STIs, is to block transmission, which in the case of sex, means to limit the amount of direct contact between an infected person and an uninfected person. Which for all these three types of sex, can be achieved through use of condoms. For oral sex specifically, this can also be achieved by using dental dams, which will also limit the amount of direct contact between an infected person with chancroid and someone who doesn't have it.