Bacterialvaginosis is a disease that's caused by the overgrowth of a type of bacteria that's called Gardnerella vaginalis, Gardnerella vaginalis. And as the name might suggest, this is the most common vaginal infection. Now I wanna put these really big quotes
around the term infection because the thing that's interesting about Gardnerella vaginalis is that it's a bacteriathat's naturally foundthe vagina. Now some may consider this to be a sexually transmitted infection, which is interestingbecause it doesn't cause
any problems until there'stoo much of it there. So when we look to the causes of bacterial vaginosis, they are all things that change the vaginal environment. That can include acts like douching, so douching, or rinsing of the vagina. The other is having newor multiple sex partners.
And finally, another known cause is the use of antibiotics. This could bethe case of somebody that has a throat infection or a pneumonia that's on antibiotics which will then attackthe bacteria that exists within the vagina andallow Gardnerella vaginalis to overgrow and cause bacterial vaginosis.
So we've touched a little bit on it here, but I wanna aw it out. So when we talk about the pathophysiology of a disease, we'retalking about the mechanism by which that disease occurs. Soorder to understandthe pathophysiology of bacterial vaginosis, we need to take a look at a sample of bacteria
that existsthe vagina. So I'll aw out someGardnerella vaginalis bacteria, and so I'll put this upour key. This is the symbol forGardnerella vaginalis. And I'll aw a few of them around here, but I also wanna show that there are a lot of other bacteriathat existthis sample. So if you really look at it here,
Distinguished future physicians welcome toStomp on Step 1 the only free tutorials series that helps you study more efficiently by focusingon the highest yield material. I'm Brian McDaniel and I will be your guide on thisjourney through Parasites. This is the 2nd tutorialmy playlist covering all of microbiologyfor the USMLE Step 1 medical board exam. We are going to the most important parasitessuch as malaria, various GI protozoa, Toxoplasmosis and Pinworm as well as some high yield treatmentoptions for these diseases. Parasites are organisms that liveor ona host. These organisms gain some sort of survival advantage (such as gaining nutrients)while their presence is often detrimental
to the host. Parasites usually don't killtheir host, but can cause disease if the parasite burden is high enough.For the exam, the most important group of parasites is Protozoa. These are microscopicunicellular eukaryotes that are usually motile. They move using a tail or foot like processes.Different species have a predilection for livingdifferent parts of their human host.The most important protozoa for the USMLE Step 1 medical board exam are Malaria, Babesiosis,Toxoplasmosis, Cryptosporidium, and Giardia Lamblia. We will cover each of them individuallyin this tutorial. The other main group of parasites that causediseasehumans is the Helminths or worms.
However, these are largely low yield materialso we will just briefly cover this group towards the end of the tutorial. We will start with Malaria, which I give ahigh yield rating of 4 on a scale from 1 to 10 based on a number of factors includinghow frequently this topic appearsretired step 1 questions. Malaria is a disease caused by the PlasmodiumProtozoa that is transmitted by Mosquitos. The most common species are Plasmodium Falciparum,Plasmodium Vivax, Plasmodium Ovale, and Plasmodium Malariae. Each of these has slightly differentcharacteristics, but for the most part these
differences are beyond the scope of StepThere is a very complex life cycle, but learning all of those details isn't necessary forthe exam. When inside a human host these parasites mainly reside inside red blood cells.ally, malaria presents with reoccurring cycles of spiking fevers and chills with othernonspecific symptoms like headache and sweating. These â€œattacksâ€� are interspersed withperiods of complete remission. The paroxysmal symptomatic periods of differentspecies of malaria occur at different frequencies, butgeneral the attacks occur every coupledays or so. Symptoms occur when mature schizonts ruptureerythrocytes releasing immature merozoites.
Anemia may be present due to this ruptureof red blood cells. The question stem almost always mentions recenttravel to a place like Africa or Latin America as Malaria is not endemic to the United States.One interesting correlation is that Sickle Cell Trait offers some resistance to certainmalaria species. This is why sickle cell trait and disease is much more commonarea wheremalaria is endemic. Sickle Cell trait actually gives a survival advantage due to its antimalarialproperty. A peripheral blood smear will show enlargedRBCs with numerous small parasite â€œdotsâ€� on Giemsa stain
Here is a picture of the histology. You don'tneed to be able to identify specific stages or species, but on the left we have matureschizonts containing merozoites and on the right you can see ring shaped trophozoites Antimalarials are a class of mediion thatcan be used prophylactically to prevent malaria, used to treat identifiedsuspected malaria,or used to periodically treat populationsendemic areas.The most commonly used antimalarials are Chloroquine, Hyoxychloroquine, Mefloquine, Primaquine.Quinine is primarily used for severe cases of malaria. Doxycyline also has some actionagainst malaria and is most often used for