music It's a typical day. A patient has noticedsome itching, or maybe an unpleasant vaginal odor. During her exam, the ian willcheck vaginal pH, examine any discharge that's present, and collect a sample. Then, it'son to the microscope. music This is where you'll gather more specificinformationabout what's causing those vaginal symptoms. We'll show you how to prepare andexamine vaginal wet preps and how to do a whiff test. The results, combined with the patient's vaginal pH test, will aidthe diagnosis.
Under the microscope, you'll be looking for trichomonads, yeast, and the clue cells associated with bacterial vaginosis. We'll show you how to recognize them. music First, the microscope itself: This is a compoundlight microscope. It has several objective lenses on a rotating mount. For our purpose,one of these has to be a 10x low power objective, and one has to be a 40x for greater magnifiion.This flat part, under the objectives, is the stage. Under the stage is the condenser. Belowthat, at the base of the microscope, is the light source. There are two knobs that controlfocus; one for coarse adjustment and one for
fine adjustment. And these are the oculars,or eyepieces. We'll come back to the microscopea minute, but first, let's look at how to prepare wet mount slides. The complete vaginal wet mount involves botha saline prep and a potassium hyoxide, or KOH, prep. When the vaginal sample was collected,the swab was placeda test tube with approximately half a milliliter of saline. So, for the salineprep, you only have to take a op of the suspension and place it on a slide. Add acoverslip, being careful to avoid trapping air bubbles. Your saline slide is ready.Place a second op of the vaginal sample on another slide and add one op of 10 percentKOH. Sniff the preparation immediately, using
your hand to waft any odor toward your nose.This is the whiff test. Note if there's a fishy or amine odor. Then add a coverslip,avoiding air bubbles. Keepmind that you must work quickly to prepare and examine thewet mounts. That's because trichomonads may lose their characteristic motility within15 to 20 minutes. Before we move on now, though, let's lookat the cast of characters you may discover. These are normal squamous epithelial cellsfoundthe vagina. They're large, flat cells with a small nucleus and a large area of cytoplasm.Note that there is some granularitythe cytoplasm.
Polymorphonuclear leukocytes are known asPolys, or PMNs. They may also be called white blood cells, or WBCs. These are small roundcells. Several lobes of the nucleus are visible within the surrounding cell cytoplasm. Findingmany PMNs may indie infection. Trichomonads are pearshaped protozoa whichmove by means of flagella. Trichomonads are similarsize to PMNs and are identifiedby their characteristic jerking movement. The actual flagella may be too thin and toorapidlymoving to be seen. A clue cell is a squamous epithelial cellcoated with enough small bacteria that at least 75 percent of the cell's border is obliterated.It may look as if someone has spread glue
over the cell and pressed itsand. Cluecells are associated with bacterial vaginosis, a conditionwhich the normal microbialflora of the vagina is disrupted. Yeast may be foundtwo forms. Pseudohyphaeare the long, tubular, branching forms. Budding yeast are paired yeast cells that resemblea shoe print. The larger part is the sole and the smaller bud is the heel of the shoe. The saline prep will allow you to see epithelialcells, PMNs, trichomonads, and clue cells. You can also see yeastsaline, but sometimesit's hidden by epithelial cells or by PMNs. Red blood cells, sperm, and bacteria can alsobe seen.
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