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
Vaginitis Candida BV Trichomoniasis Wet Mount Whiff Test Vaginal pH Trich Albicans gardnerella
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 vulvovaginal infections. This is the 3rd tutorialmy playlist covering allof microbio. Vulvovaginitis (AKA Vaginitis) is inflammationof the lower genital tract. It is usually due to infection, but there are a wide varietyof causes. During this tutorial we will focus on the 3 most important causes of vulvovaginitisfor the medical board exam (trichomonas, candida and BV). However, you should know that othertypes of vaginitis include mechanical irritation,
allergic reactions (to soaps or feminine products)and a variety of other infections. Atrophic Vaginitis is a common cause of vaginitis inpostmenopausal women and we will cover thata later tutorialthe GYN section. Gonorrheaand Chlamydia present primarily with cervicitis, but it can also cause vulvovaginitis. GCwill be covered laterits own tutorial. We will start with a few different tests thatwe will use to differentiate between the different infections.Wet Prep (AKA Wet Mount Test) is a microscopic examination of vaginal discharge used to differentiatebetween different types of vulvovaginitis. The vaginal specimen is obtained using a speculumand a que tip similar to how one gets a pap
smear. Then the specimen is rubbed onto aglass slide. One half of the slide has a op of saline added to it while the other halfof the slide has a op of 1020% KOH (Potassium hyoxide) added to it.When Saline is added it makes it easier to view clue cells for BV flagellated motilecells for trichomonas. The KOH kills bacteria and vaginal cells leavingonly yeast cells. This makes it easier to view the psuedohyphae and budding yeast presentduring vulvovaginal candidiasis. KOH is also alkalotic so it can be used fora â€œWhiff Test.â€� In this scenario when the alkalotic KOH is added to a sample containingBV it will create an amine or fishy smell.
This is a similar principle behind how thesmell of BV can increase after unprotected sex since semen is alkalotic. The normal vaginal pH for a reproductive agewoman is about 4, while the normal vaginal pH before puberty and after menopause is about7. During puberty there is an estrogen guided increasethe growth lactobacilli flora.These bacteria break down glycogen into lactic acid which lowers pH from about 7 to about4. Now that you know the normal values you can apply it to diseases. Usually, BacterialVaginosis Trichomonas have alkalotic pH (gt;4.5reproductive age women) while candidahas normal pH (lt;4.5). pH paper can be tested
by using pH paper on vaginal discharge. You can see here at the top right corner thatI give BV a high yield rating of 3 on a scale from 1 to 10. If you want to learn more about that ratingsystem you can go to my website or click on this orange box here if you are watching thistutorial on a computer. Bacterial Vaginosis (AKA BV) is a polymicrobialinfection caused by the overgrowth of normal flora. The key bacteriathis infectionis gram negative Gardnerella Vaginalis. Clue cells are visible on the saline portionof a wet prep. A Clue Cell is a sloughed mucosal
squamous epithelial cell coveredmany adherentcoccoid bacteria (Gardenerella Vaginalis). Here is a picture comparing normal squamousepithelial cells with a few stered lactobacill to squamous cells that are coveredthousandsof adherent garenerella bacteria. Here is one more pic. You can see on the leftwe have a normal squamos epithelial cell with a few WBCs. On the right we have the darkerClue cells. Finally I have a photomicrograph to look atin case you see that on your test. A thinwatery graywhite discharge is presentA fouls smell is present and often described as an Amine Odor or Fishy Smell. This smellis intensified after unprotected intercourse