MBI 111
Microorganism
FAQs and Answers
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Since some students frequently have neither the time to schedule appointments with faculty, nor are comfortable with asking questions in a large classroom setting, those students are encouraged to e-mail their questions or submit them using Niihka. Answers will be posted here. Please use these questions and answers as a resource for greater understanding of issues and concepts regarding Microorganisms and Human Disease. Table of Contents:
Lecture NotesQ. How do I access the notes off the web? A. First, you need to have Microsoft PowerPoint installed on your computer. Then you would navigate the the notes that you wish to download and click on the link. As you download the notes, pay attention to where on your hard drive the file is being saved. Alternatively, if you don't have PowerPoint, you can use a computer in Brill Science Library or any of the campus computer labs. Many of those computers have PowerPoint already installed.
Q. Is it possible to reschedule the date of my final exam. I was hoping to be able to take it earlier in the week since my only other exams are on Monday of finals week. A. Unfortunately no. Our chair has given the faculty explicit instructions; faculty are to give their final exams only at the scheduled time. I'm sorry but it's out of my hands.
Q. Is our final exam cumlative? A. No.
Before Exam 1Q. I'm getting caught up with a lot of dates, names, terms and definitions. Do I need to be memorizing all of these facts, or are you concerned with more general information? I'll give an example. For smallpox, we learned that it is obtained by inhalation of a virus, the list of symptoms and the mortality rate. I know that we discussed a lot of numbers and percentages so far, but is it enough to know that it was deadly and greatly feared, or do we need to know that the mortality rate was 45%? A. I would not ask for a specific mortality rate, but it would be valuable to know that the mortality rate is high. It provides context for why the disease was greatly feared. In general, terms and definitions are important to know, but dates and numbers should be learned in a qualitative mannor.
Q. I have a question about toxins, adhesins, invasins, and evasins. Are they all microorganisms? Are they something that we acquire from the outside world, or are they already existing in our body that mutate and make us sick? A. Toxins, adhesins, invasins, and evasins are not microorganisms, but rather they are virulence factors - properties of microorganisms that enable them to make us sick.
Q. I'm getting all of these terms confused. Microorganism, organism, pathogen, bacteria, eukaryote, prokaryote. Are these all forms of microorganisms that we acquire or already live in our bodies? Are pathogens, bacteria, parasites, eukaryotes, and prokaryotes all microorganisms? Are they all bad and cause disease, or are some forms of them safe and cause no harm? A. Organisms are either prokaryotes and eukaryotes, depending on their cell structural organization. Eukaryotes include multicellular and unicellular organisms, including animals, plants, protozoa, fungi and algae. Prokaryotic organisms include the bacteria and the archea. We use the term microorganism to describe organisms that require assistance, such as a microscope, to see. Among these different microorganisms are some that can cause disease (pathogens), some of which infect without causing disease (normal flora) and some of which do not infect or cause disease.
Q. I'm confused on the differences between a parasite and a pathogen. Are parasites both helpful and harmful? A. A parasite is an organism that benefits from a symbiotic relationship in which its host organism is harmed. A pathogen is an biological agent that causes disease. The difference between these terms is largly semantic. In the case of parasitism, the type of harm is not specified. In the case of the pathogen, the harm is defined as a disease.
Q. What exactly is virulence? Is virulence how bad the bacteria is? Or is virulence how the bacteria go about getting into the body? A. Virulence is defined as the ability of any agent of infection to produce disease. The virulence of a microorganism (such as a bacterium or virus) is a measure of the severity of the disease it is capable of causing. While it is necessary for a microbe to gain access to the body to cause disease, the virulence of the microbe best describes what the microbe does once it has gained access.
Q. How do we know if a virus or bacteria causes a disease? Would the pneumonic plague be caused by a virus and the bubonic plague by bacteria? A. The best way to determine whether a disease is caused by a bacterium or a virus is to memorize it from the notes. There is a clue about treatment that can help help remembering. Typically, antibiotics can be used only to treat diseases caused by bacteria. They are ineffective against viruses. With respect to plague, all forms of it are caused by a bacterium that goes by the name of Yersinia pestis. The difference in symptoms has to do with the fact that different tissues/organs are infected with the bacterium
Q. Would it be possible to see a sample of a past exam from the MBI 111 class? A. I generally don't make my past exams available to students for two reasons. First, the distribution of exam info can be quite lop-sided, in that many students will be unable to access the exam for a variety of reasons, while others (particularly students who belong to organizations that can accumulate exams in long-term files) have easy access. Second, by making the exam available, I am limited in recycling some questions from previous exams. I would have to write each exam from scratch (and I already have enough work to do). I feel that students learn more about microbiology from studying from their notes rather than studying past exams.
Q. Are MBI 111 students going to held accountable for the names and dates of the people who helped in the discovery of microbes (inventors and others)? Would they show up on a test? A. Students will be responsible for names, but not specific dates. However, the general period of time is important (it helps to put the discoveries in perspective), thus one should know generally when discoveries were made.
Q. Will we be discussing the supplemental readings in class at all? Are any of the supplement readings going to be on the test? A. Although we will not be discussing specific supplemental readings, some of the lecture material will be derived from the readings. The supplemental readings are provided as an additional resource for student inquiry. If you are interested, you can read the articles. Since information from the supplemental readings overlaps with the lecture, some information in the supplemental readings will be on the test. However, with the possible exception of a bonus question, I will not be testing material in the supplemental readings that was not covered in lecture.
Q. Is it necessary for us to remember all of the microorganism names for the exam? There seem to be so many and I was just wondering if we are going to be held accountable for all of them. A. Although I would like it if students could remember some of the microorganism names, I tend to focus my questions more on the names of the diseases (i.e cholera-causing microbe) rather that the microbe's name (Vibrio cholera). I would not rule out their being a microbe name or two on an exam, but if I were you, I would not emphasize their names in my studying.
Q. You give a lot of examples of microorganisms in your lectures. One of the more recent examples includes the different diseases which commonly attack individuals affected with AIDS. I was wondering if these examples are important to us past the point where they serve as examples of what would be in this case opportunistic pathogens. In other words are we going to be tested on what diseases affect individuals with AIDS or are these just methods to illustrate points? A. Eventually you will be asked specifically about those specific opportunistic pathogens (in the last 25% of the course). However, at this point, you should focus on understanding what an opportunistic pathogen is; the examples provided serve to illustrate that immunocompromized individuals suffer life-threatening infections with unusual microbes.
Q. I was wondering if our readings in the text serve to supplement your lectures or if your lectures serve to supplement our readings? If it's in the text and you don't go over it in lecture is this material we will be tested on. A. Although the readings in the text should serve to supplement the lectures, and the lectures are your primary reference (and the should be your primary emphasis in studying), the text should not be ignored. There may be a minor component in the examination that draws from material in the text and not in the lectures.
Q. In the syllabus it stated that the exams would be over the material from the lectures, text, and the student's oral reports. If there are going to be questions over the oral reports, how should we prepare for these questions. A. First of all, it would be useful to pay attention to the reports. It is of little value to the class for students to be giving reports while the class sleeps through them. Second, students should take a few notes regarding the main point(s) of each report. I will not be testing to great depth on the reports, but I will try to determine if students were paying attention.
Q. How long before an exam will a study guide be posted on the web page, if you post study guides at all? A. The study guides are already posted. You should note that I will not be posting a study guide for the first exam. I reserve the guides for when the material becomes more difficult (i.e. exams 2, 3 and 4)
Q. Have you decided yet on how many questions will be on each test? How much preparation do you advise? Do you believe that it is going to be over general information or should we know the "very specifics" and many examples? A. There will be 40 multiple-choice and matching multiple-choice questions. The amount of preparation depends upon the individual. Certainly general information is important, as well as specifics; however, I try not to write questions that examine the students ability to recall minutia (i.e., I will not ask for the species of bacterium that Stanley Falkow used to demonstrate invasiveness genes, but I think that questions about the nature of invasins and what invasiveness means for a microorganism is fair game).
Q. I was wondering, when do we get our results of how we did on our exams? Is it the same day? Also, are the special instructions to follow in order to obtain your score (regarding the internet)? A. I will be posting scores shortly after receiving results from MCIS. This is usually within a day (since the upcoming test is on Friday afternoon, I might not be able to post results until Monday). Similar to what students do to find their report dates, exam (and report) scores will be available from the class home page.
Q. Is it possible for us to do two written reports instead of an oral report? A. No. In fact, you are required to do two written reports, one of which you also present to the class. The reason for the oral portion is to contribute to the material to which students are exposed in this class, in essence contributing to the curriculum. To not do the oral portion of the report would be to deprive your classmates of your insight and experience.
Q. Do you curve the grades on your examinations? A. Yes. The scores that are reported on Blackboard have already had the curve applied to them. Typically, I apply a curve if the class average falls below 80%. Final grades are based on the percentage of points that you accumulate during the semester. Since exam scores have already been curved, their will be no additional curve, and the grading scale in the syllabus can be used to estimate your final grade.
Q. Are we going to need to know that measles and malaria are a clinical disease or other questions about specific microorganisms and their effects. Could you please elaborate on my question also? A. You would need to know what a clinical disease is. I could ask a question like, "Since measles has obvious signs and symptoms like fevers and rash, this would be an example of:
Q. What exactly is "variolation," the concept that Lady Mary Montagu promoted? A. Variolation is the technique used to prevent fatal smallpox infection. Scab material from a mild (or less pathogenic) case is administered, in an attempt to give the person a milder case. Once someone has survived smallpox, regardless of the virulence of the virus, one has lifelong immunity.
Q. What is the difference between normal flora and avirulent? Are they the same thing? A. Not exactly. Normal flora are those microorganisms with which we have a commensalistic or mutualistic symbiosis. They live on us, but don't normally cause disease. Avirulent microorganims are those that don't cause disease, but they might not live on us in some kind of symbiosis
Q. On the study guide, it says that for each disease we should know the etiologic agent....what is that?
A.
The etiologic agent is the microbe that causes a particular disease.
Q. I was wondering what the principle differences were between antibiotics and vaccines, and what an antibacterial agent is. A. An antibiotic is a drug that you take to kill a bacterium. It is called an antibiotic if it is a chemical that is produced by other life forms (i.e. penicillin from the mold Penicillium). A vaccine is a preparation derived from a pathogen that stimulates the immune system to kill the pathogen, or prevent the infection of the vaccine recipient. An antibacterial agent is a chemical that kills bacteria (i.e. a disinfectant, an antiseptic, an antibiotic, or a chemotherapeutic agent).
Q. I was wondering if we are able to see what questions we missed on the exams?! If so, HOW? A. Yes you can see your exam and answers. To do so, you should come see me during office hours (if possible).
Q. What are the factors that may affect the result of the Gram-staining method? A. The main factor that influences the result of a Gram stain (whether an organism is classified as Gram positive or Gram negative) is the structure of their cell wall. The Gram positive cell wall is much thicker than that of the gram negative organism, thus it retains the dark purple stain. The Gram negative cell wall is much thinner, and it is readily decolorized with alchohol.
Before Exam 2Q. Should we focus our studying more on the study guide or more on the PowerPoints from class? Which are more important? A. Actually, I consider both to be equally important. The PowerPoints provide the info that you would need to answer questions in the study guide, as well as to answer similar questions that might make it into an exam.
Q. Will we have to label parts of prokaryotes and eukaryotes? A. No, but you should be able to describe the functions of the parts that are discussed in detail.
Q. Are both prokaryotes and eukaryotes able to cause disease? A. Yes they are, but most do not. The prokaryotes are bacteria - some are soil dwellers, some are water dwellers, and some inhabit plants and animals. Some species of bacteria are capable of causing disease, but most do not. The eukaryotes include plants, animals, green algae, fungi and protozoa. Some of the unicellular eukaryotes, such as fungi and protozoa, are also capable of causing disease, but most do not.
Q. Regarding questions pertaining to the oral reports, will there just be one question, similar to the question on the first exam? A. At least one.
Q. What differences between prokaryotes and eukaryotes should we know? A. I would know distinguishing features. Divide the features of each cell type into features in common between cell types, and features that are unique to each cell type.
Q. What is the technical difference between a nucleus and a nucleoid, refering to the eukaryote and the prokaryote. A. The technical difference is that a nucleus (in eukaryotic cells) is contained within a membrane within the cytoplasm. A nucleoid (in prokaryotic cells) is also within the cytoplasm, but has no bounding membrane.
Q. Could you define the term "lyse"? A. From Webster's: To cause dissolution or destruction of cells
Q. What is "morphology". I don't have a definition in my notes and it is not in the book. A. Morphology is the study of forms and structure, so the morphology is the form and structure that the organism has.
Q. I am confused about what exactly a spore is. I know that it is related to fungi and is dormant, but what is its function? How does is cause damage. I thought that dormant implied that it is dead, but dead fungi should not be able to cause damage. Can you help clear this up please? A. A spore is dormant, meaning that it has mimimal metabolic activity, but it is far from dead. Consider it to be in a resting state, such as a sleeping person, or a tree in winter, or a seed. It has the potential to become active when conditions are right. It also has the opportunity to spread from its current location because of its small size; it is easily dispersed. When conditions are right, the spore will germinate, changing its morphology to that of a yeast or mold. Then it is capable of causing disease
Q. Regarding structures in bacterium, what is the endospore (this part is a little confusing in the notes). A. The bacterial endospore is analogous to the fungal spore. Although a bacterium generates a spore not as part of sexual reproduction (as fungi do), but as a response to inhospitible growth conditions, it allows it to persist in the environment, and is a source of disease.
Q. When we were talking about the bacterial growth curve and compared it to the pattern of disease progress, I understood that they are almost identical. So, what is the difference? Could it be that bacterial growth curves are specific for bacteria, but the pattern of disease progree could be viral, bacterial, fungal or protozoan (independent of the nature of the etiologic agent)? A. The bacterial growth curve is a study of the growth of bacteria in culture media in the laboratory. One could construct similar growth curves for fungi, protozoa and viruses. The pattern of disease progress relates to how symptoms change during an infection. The main similarity is that the pattern of change in symptoms is similar to the change in microbe numbers. I would not consider growth curves to identical of disease progression. Rather, I would use it as a tool to interpret the effects of interaction between a microbe and the host. For example, in a growth curve the stationary phase represents a time in which microbial reproduction equals microbial death. One might see such a set of conditions in a human host when antibiotics or the immune system has begun to kill the infecting microbe. Q. I am getting confused about the difference between selective media and differential media. It seems that diffential media is selective media only more specific. A. Selective media only allows certains types of bacteria to grow; it blocks the growth of others. In that way it is selective with regard to the types of bacteria that can grow on it. Differential media will allow all types od bacteria to grow, but ingredients in the media will cause some of the colonies to appear different from the rest. It allows one to tell the difference between types of bacteria. Some of the confusion may be occuring because there are media thAt are both selective and differential, i.e., MacConkey's agar.
Q. What is the difference between an abscess and a carbuncle? Am I right in thinking that a carbuncle is just several abscesses in one location? A. Pretty much so. A carbuncle may invade a little deeper into the tissue.
Q. In the notes what does the word "Cardinal" refer to regarding the signs of inflamation? A. From Webster's: Of prime importance; chief; principal. Q. In the topic of antigens, are all antigens autoantigens and only some antigens alloantigens? A. Most antigens are neither autoantigens or alloantigens. The terms autoantigen and alloantigen are reserved for molecules in people that can act as antigens under special circumstances. If a person has an autoimmune disease, their immune system is recognizing and attacking some part of their own body. The part of the body or cell that is triggering this response is the autoantigen. An alloantigen is a part from a different person's body against which one's immune system responds. Examples would include transplanted organs or transfused blood.
Q. What does the root word Lymph mean. A. Lymph is a clear, yellowish, coagulable fluid, circulated by the lymphatic system, that resembles blood plasma or serum, but contains mainly lymphocytes and fats.
Q. Are the psychrophiles, mesophiles, and the thermophiles a category of bacteria based on the temperature in which they can reproduce? A. Yes.
Q. What exactly is phylogeny? A. According to Webster's
Q. In the study guide, it says describe four different types of Ag-Ab reations and show how each contributes to specific defense in the body. Can you help!? A. Antibodies can neutralize viruses and toxins, lyse bacteria, clump microbes and their products into larger complexes that are cleared from the body more easily, and increase the rate of phagocytosis of those particles.
Q. How similar to the format of questions on the last test will be the questions on this test. That is to say, of what are you expecting us to be able to demonstrate a knowledge ? (i.e. general concepts, specific terms) A. The format of the questions will be similar, with the exception that greater emphasis will be based on scientific concepts and processes, since these were covered in more detail. I recommend letting the detail asked for in the study guide serve as a model for the quality and depth of information you should know.
Q. I was wondering what PMNs were… I was reading through the notes and couldn't figure out what they were. A. PMN is an acronym for PolyMorphoNuclear cell. This cell, also known as a neutrophil, is a phagocyte. Unlike macrophages, the PMN is not capable of antigen presentation.
Q. Also, what is the difference between IgG and IgA? A. IgG forms the main antibody component (80%) of blood. It also can cross the placenta. IgA is the main secreted antibody. It can be found in breast milk, saliva, tears, and secretions into the repiratory, intestinal and urogenital tract.
Q. Does a flagella provide any advantages other than providing movement to the bacterium? A. Not really.
Q. What are the dynamics of a bacterial growth curve A. The dynamics are how and why the curve goes up and down.
Q. What are the variations of the three major shapes of bacteria? A. This would include (but is not limited to) chain formation, packet formation, occuring in pairs, etc..
Q. You said in the helminth section of handout 3 that there are multicellular eukaryotes with no cell walls. Wouldn't that make them prokaryotes? I thought that eukaryotes had cell walls as a distinguishing factor. A. No. Cell walls are not a distinguishing feature of either eukaryote or prokaryotes. Cell walls can be found on plant and fungal cells (eukaryote) and bacteria (prokaryote). Animal cells (eukaryote) have no cell wall.
Q. Our book, on page 446, says that Ab IgE is located in the skin, respiratory tract, and tissue fluids while IgA is located in the saliva, mucus, and secretions. However, our notes say that IgA is secreted into the respiratory and GI tract. Which one is correct? A. Both. IgE is found bound to specialized cells (mast cells) that are located in the skin, respiratory tract, and tissue fluids. IgA is secreted into the respiratory, urogenital and G.I. tract, where it mixes with saliva, mucus and other secretions.
Q. Are abscesses and carbuncles the ways in which inflammation develops on the skin, or do those also include the dilation of blood vessels, increased capillary permeability, etc? A. Inflammation is a process that begins with dilation of blood vessels and increased capillary permeability, etc, which can result in the formation of abscesses.
Q. Is inflammation caused solely by mechanical, chemical, physical, or biological means? A. Technically, inflammation is caused in response to tissue damage. Any way that one can cause damage to tissue (mechanical, chemical, physical, or biological means) results in inflammation.
Q. What is the difference between a PMN and a macrophage??? A. Although both are phagocytes, they also have some specialized functions. The PMN is the first phagocyte recruited to sites of inflammation. They are loaded with lytic enzymes, and are very efficient at phagocytic killing. Macrophages are less capable of phagocytic killing unless activated, but they can also serve as antigen-presenting cells, thus they can help in the activation of helper T cells.
Q. Does CTL, involved in the proccess of cellular immunity, stand for cytotoxic T lymphocyte or cytotoxic T lymphokine? A. Cytotoxic T lymphocyte (the cell).
Before Exam 3Q. Question #1 from the study guide says to compare and contrast strep. What do we need to know about Streptococcus pyogenes that makes it different from any other form? A. You need to be able to distinguish the various types of S. pyogenes infections based on their symptoms, whether or not exotoxins are involved in generating the symptoms, and the types of immunological complications that can be associated with the diseases. Basically, how are they similar and how are they different?
Q. For study guide question 2, you want us to compare and contrast immunization and treatment of Streptococcal pneumonia and TB. They both are becoming resistant to antibiotics and both have a vaccine. What is different about the diseases? A. You need to compare a little deeper. TB uses a live bacterium (BCG) for the vaccine, while streptococcal pneumonia uses a cocktail of pneumococcal capsule. Yes, both organisms are becoming resistant to antibiotics, but in addition, treatment for TB requires 6-9 months of treatment, whereas the pneumococcus responds quickly to an effective antibiotic.
Q. Is puerperal fever the same as puerperal sepsis? A. Yes. It's also known as child-bed fever.
Q. You ask about the staining reactions and diagnosis for the tuberculosis organism. I was wondering exactly how the staining process works, and how you get a diagnosis from it? A. The staining reaction is the acid-fast stain. It is a differential stain used to identify members of the genus Mycobacterium. While mycobacteria are difficult to Gram stain, they will stain red when treated with carbolfuchsin and heat. When washed with a dilute acid-alcohol solution, they retain the red color, hence they are called "acid-resistant" or "acid-fast". Other bacteria will lose their color when washed in dilute acid-alcohol. If you detect acid-fast bacteria, this will assist you in diagnosing a mycobacterial disease.
Q. I was wondering what you meant by question #21 in the study guide regarding the importance of E. coli as a pathogenic bacterium. What would a pathogenic bacterium be, and why would it be important? A. Although E. coli has classically been recognized as normal flora, and is a laboratory microbe for genetic research, we have become more aware of its importance as a pathogenic bacterium ( a microbe that causes disease). In particular, the emergence of the O157:H7 strains in contaminated hamburger and other foods, and the increasing numbers of infections and hemolytic uremic syndrome due to this microbe has change the way the government inspects meats, and has encouraged the introduction of better practices for the safe handing of meats. So the importance of this microbe is not only the increasing numbers of infections, but also how it has affected our approaches to safe food handling.
Q. Regarding the genetics of the influenza virus, do we just need to know that it shows heredity as it reproduces new particles identical to the original ones, or is there more to know? A. There is more to it than that. Influenza virus is prone to mutation, resulting in antigenic drift. Not all virus particles are always identical due to this mutation. Because of these mutations, the important surface antigens, H (hemagglutinin) and N (neuraminidase) can change from year to year. In addition (but more rarely), there are virus reassortment events, called antigenic shift. This happens when two different strains of flu virus infect the same cell and their gene segments mix (each flu virus has 8 gene segments). The viruses that have mixtures of genes from each of the original strains will essentially be a new type of flu virus. For these reasons (antigenic shift and drift), we will always need to develop new flu vaccines for each flu season - the virus keeps changing.
Q. Why aren't antibiotics effective with botulism food poisoning? A. In cases of botulism food poisoning, there is no infection, so there is nothing for the antibiotic to kill. The disease is caused by ingesting a microbial poison (toxin).
Q. is there a vaccine for shingles (herpes zoster)? A. Yes. Since chickenpox and shingles are caused by the same virus (varicella zoster), the shingles vaccine is the chickenpox vaccine
Q. What is the virus that causes German Measles (Rubella)? A. It is the Rubella virus.
Q. In comparing the viruses that cause measles and german measles, should we just know that the virus for measles is related to the mumps virus? A. You should also know that the viruses that cause measles (rubeola) and german measles (rubella) are unrelated.
Q. What is the congenital transfer of both Measles and German Measles? A. Congenital transfer of german measles is the infection of the fetus from an infected pregnant woman. There is no congenital infection with measles.
Q. Question 10 on the review sheet is referring to which diseases specifically? A. It refers to all of the diseases in the respiratory infection notes.
Q. Are we going to have to memorize all of the agents for each disease for the exam? A. I will try to refer to the diseases by their more common names when possible.
Q. For the pathogenesis of each disease will we just have to be familiar with the steps or memorize them? A. I would know what each microbe is is doing to cause damage. Is there a toxin, what does it do, is the organism invasive, etc.
Q. What are the "R Factors"? A. R factors are plasmids that contain antibiotic resistance genes (R for resistance).
Q. When you ask for the symptoms of anthrax bacillus, do you want the symptoms of pulmonary anthrax, gastrointestinal anthrax, and anthrax of skin, or just one of those? A. All of them (many overlap).
Q. As far as Clostridium is concerned...do we just need to know the differences between Clostridium tetani and Clostridium perfringens, or are there other diseases caused by the Clostridium species? A. You should also consider Clostridium botulinum.
Q. What are the three different Staphylococcal skin diseases? I can only find 2 in the notes. And what do you mean by "salient differences? A. Abcesses, scalded skin syndrome and impetigo contagiosum are the three. As for salient differences, Webster's defines salient as prominent or conspicuous.
Before Exam 4Q. Today in class you suggested that we read the supplemental reading for the freshman survey. Where can we find that? A. The supplemental readings are available online through our classes website. The article is called "AIDS knowledge and sexual attitudes."
Q. I have had a hard time finding a few terms, they are not in the notes or in the book. They are the following: chlamydial pneumonia, chlamidial opthalmia, chlamydial pharyngitis, and chlamydial proctitis. If you could help me with the definitions or indicate where I could find the definitions that would be wonderful. A. They are refered to in your class notes at the bottom of the page on Chlamydia. As far as working definitions, these diseases are similar to those caused by Neiserria gonorrhoeae - similar transmission and symptoms. The only disease unique to chlamydia in this list is chlamydial pneumonia, which is transmitted to the newborn during passage through the birth canal.
Q. I am not very clear on what the significance of being named a TORCH disease is. Can you help?. A. TORCH is an acronym for toxoplasmosis, other infections, rubella, cytomegalorvirus infection, and herpes simplex. These infections are grouped together because they all cause congenital infections whose clinical manifestations are similar, although symptoms may vary in degree and time of appearance. Essentially, they can all cause birth defects.
Q. Is there a treatment for Tertiary Syphilis? The notes say that antibiotics are the treatment for Primary and Secondary stages, but nothing is said for Tertiary. A. That is because antibiotics are much less effective in treating tertiary syphilis. Treatment consists of higher doses of antibiotic, for longer duration, but often fails - particularly with neurosyphilis. The symptoms of tertiary syphilis are an immunological consequence of long-term syphilis infection, not specific damage caused by the bacterium.
Q. Can you please explain the significance of HBsAg in Hepatitis B? A. Hepatitis B surface antigen is an important part of the nucleocapsid. In addition, its presence is the blood is diagnostic of hepatits B infection. Furthemore, the vaccine for hepatits B is made of HBsAg.
Q. What is ELISA? A. ELISA stands for enzyme-linked immunosorbant assay. It is a test that detects either specific antigen or specific antibody. A positive reaction leads to a color change.
Q. Do we need to know, for example, that rabies is a helical-bullet shaped virus? A. While I probably would not test for this kind of information individually, it may well be a clue to the diagnosis of a specific disease. I would know it to be safe.
Q. What should we be focusing on in the supplemental readings? It seems as if many of the articles (mostly the AIDS articles) are very clincial. A. I would try to understand the main points of each article, as well as to gain an appreciation of the details.
Q. What is the main difference between Gonococcal Urethritis and Chlamydial Urethritis? A. First, the trivial answer; one is caused by Neisseria gonorrhoeae and one is caused by Chlamydia trachomatis. But now we enter the realm of subtleties. Chlamydia is more likely to cause PID in women, but it is also more likely to be asymptomatic. Different diagnostic techniques are employed. Neisseria can be cultured on agar and will appear in a gram stain. Chlamydia requires tissue culture (a source of cells to infect), and requires fluorescent antibody staining to easily detect it (but both can be detected by ELISA tests).
Q. What are the complications of gonorrhea and what organs does Neisseria gonorrhoeae affect? A. First, the complications of gonorrhea are typially pelvic inflammatory disease and infertility due to scarring of the falopian tubes. Second, the tissues affected depend on how the disease was acquired. The gonococcus can infect the urogenital tract and ascend to the uterus and falopian tubes. It can also infect the throat (pharyngitis), the rectum (proctitis), and the eyes (ophthalmia). Infection of the eyes can lead to permanant scarring of the cornea (cataract).
Q. What is the relationship between Herpes and cancer? A. There is a statistical correlation between infection with Herpes simplex type II and cervical cancer in women.
Q. What exactly are oocysts? Are they feces? A. Oocysts (a.k.a. cysts) are dormant yey infectious form of some protozoan parasites. Thet possess a cell wall that protects them from the environment. When the protozoan parasite is an intestinal pathogen, the oocysts are typically shed in feces.
Q. What is lymphadenopathy? A. From the American Heratge Dictionary, lymphadeopathy is a chronic, abnormal enlargement of the lymph nodes, usually associated with disease. This is typically a result of immune system involvement, and proliferation of T and B lymphocytes in response to antigenic stimulation.
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