FUN2: 11:00-12:00Scribe: Ryan O’Neill

Friday, November 21, 2008Proof: Caitlin Cox

Dr. WaitesPathology of Infectious Disease (2)Page1 of 5

SAG – Superantigens, SSPE - Subacute sclerosing panencephalitis, HPV - Human papillomavirus, CMV - Cytomegalovirus viral, ELISA - Enzyme-Linked ImmunoSorbent Assay

  1. Bacterial Superantigens [S34]
  2. SAGs are toxins (such as Toxic Shock Toxin caused by Staphylococcus Aureus) cause a massive “cytokine storm” that activate T cells at great orders of magnitude leading to capillary leak and shock.
  3. [S35] Pathogenesis of Viral Infection (SKIPPED)
  4. Viral Infection and Multiplication [S36]
  5. Remember from previous lectures, to cause disease viruses have to attach, penetrate, uncoat and remove capsid and then transcribe mRNA from viral nucleic acid.
  6. End result: replication of viral nucleic acid and proteins. Then they have to release themselves from the host cell either by lysing the host cell or by budding.
  7. Slide shows HIV virions budding from host cell.
  8. Attachment to Host Cell Surface Adhesins & Receptors: Influenza Virus [S37]
  9. Viruses have to attach to a host cell in order to penetrate it and the Influenza Virus is an example of this.
  10. It recognizes receptors on the host cell.
  11. Hemagglutinin - binds to the cells.
  12. Neuraminidase - facilitates release of virus.
  13. The changes in the antigenic structures of the hemagglutinin or the neuraminidase is called antigenic drift.
  14. In comparison, antigenic shift occurs when you have a major new virus that has evolved and this is what causes pandemic outbreaks of severe influenza because no one has immunity to it.
  15. How Viruses Kill Host Cells [S38] – 8 virus types
  16. Understand what the virus actually does to the host cell. There are many different methods. Just like bacteria.
  17. Polio – invades nerve cells and kills the motor neurons of the spinal cord, that is why you get paralysis and as a result of this cytotoxic effect it inhibits DNA & protein synthesis.
  18. Measles - causes a rash and produces giant cells by inserting into the host cell membrane and damaging it and the host cells fuse with one another. This is how the giant cells are produced because of the proteins that are inserted into the cell membrane.
  19. Influenza – invades the respiratory epithelial cells in the trachea and it utilizes all of the machinery in the host cell to replicate in the cells and lyse them to release the virus to other cells.
  20. When you lyse the host cell, a hole is left in the epithelium of your trachea and this is why you get a cough and irritation in the trachea.
  21. The reason so many people die from influenza is because you have killed off all of the epithelial cells lining your airways and can get a severe pneumonial bacteria infection because they invade due to the killing of the host cells of the epithelium. The bacterial pneumonia is actually what causes death in people with the flu and they never would have gotten the pneumonia if they had never gotten the flu.
  22. Hepatitis B - recognition of viral proteins on cell surface in the liver by immune cells that attack infected cells and your liver cells die and you get fibrosis and scarring and ultimately cirrhosis of the liver because the immune system is trying to kill the virus and kills the host cell in the process. Most of the disease you get in hepatitis is related to how strong your immune system is.
  23. [S39]
  24. HIV - damage host immune cells (killing the CD4 lymphocytes by the HIV virus) leading to opportunistic infections (e.g. Toxoplasma infections, Cryptococcal infections, Candida infections and all of the other infections common in people with HIV).
  25. Polio – swallow the poliovirus, it travels to the GI tract and then the blood stream and eventually into the ventral horn cells of the spinal cord. The virus kills off the motor-nuclei of the spinal cord and the muscles that are innervated by the spinal nerves don’t have the innervation anymore and your muscles no longer work and atrophy and die.
  26. Even though the virus never went anywhere near the muscle cells, it indirectly killed them.
  27. SSPE – 1% of people who got measles developed an encephalitis that was fatal, so the SSPE is a viral infection that occurs after latent period (occurs with measles of the brain).
  28. HPV - Cell proliferation/neoplasia
  29. There are many types of cancer associated with viruses because viruses directly transform cells and induce neoplasia. The best-known type is the HPV that causes cervical cancer. Now we have a vaccine against HPV that is designed to protect women against the virus, therefore the cancer.
  30. Several different viruses can cause a tumor.
  31. [S40]: Measles Virus “Giant Cells”
  32. This is the rash that you see with measles because of hypersensitivity to cutaneous viral antigens. These are the giant cells that occur as a result of the effect of the virus on the host cell.
  1. Host Response to Viral Infection [S41]
  2. Inflammation that occurs when a virus enters a host cell is mononuclear.
  3. Suppose someone comes into the hospital with a headache, photophobia and a stiff neck. The big question then is, do they have viral or bacterial meningitis? The treatment is very different for both.
  4. Antibiotics for the bacterial, bed rest for the viral.
  5. A lot of neutrophils in the spinal fluid would suggest bacterial, a lot of mononuclear cells would suggest viral.
  6. Antibody production to prevent (just like in bacterial infections) attachment, penetration & uncoating.
  7. Many vaccines that prevent infections are by the stimulation of antibody production.
  8. Interferon production is part of our host immune system to protect against viral infections by inhibiting their translation of viral proteins and replication, and by enhancing T cell and NK cell activity. These are naturally occurring, but we don’t produce enough of it to cure a virus, so interferons are now being used for treatment of viral infections.
  9. Cellular immunity is important against the protection against viral infections.
  10. When HIV destroys cell immunity, the body will be exposed to opportunistic infections.
  11. [S42]: Viral Latency
  12. Viral latency occurs with the following viruses:
  13. Herpes Viruses
  14. Varicella zoster
  15. Chickenpox – the virus doesn’t leave the body, but lies dormant in the dorsal spinal nerve ganglia. When you get older the virus may come back and produce vesicular eruptions and cause the neurological condition of the Shingles.
  16. Prions [S43]
  17. Not really viruses, but neuron proteins (PrP) that undergoes conformational changes.
  18. Infectious & transmissible
  19. Sporadic & familial forms
  20. Examples
  21. Creutzfeldt-Jakob Disease and the infection control implications - 4 or 5 cases per million. The big problem with this is that you cannot sterilize adequate instruments to treat patients where body fluids are going. Spinal fluids are not handled with the instruments in the laboratory because the disease can be reproduced. Regular blood specimens are not generally infectious, but spinal fluid, ocular tissue and brain tissue can be. No autopsies are done with these patients. Only disposable instruments are used.
  22. Bovine Spongiform Encephalopathy (Mad-Cow Disease) – produce a spongiform encephalopathy.
  23. These two diseases are incurable and cause dementia and death in several months.
  24. Remember, all of this is related to prion disease and these two are the most common types.
  25. [SQ1]: Why isn’t there more concern with these diseases and their lack of sterilization?
  26. [A]: Because they are so rare.
  27. [SQ2]: How have studies shown that they can be killed?
  28. [A]: Can kill them with bleach by denaturing since they are proteins. There is no cure for these and they are fatal. Just better to avoid contamination altogether.
  29. Main point: you can transmit the disease by spinal fluid, brain tissue and ocular tissue.
  30. Fungal Diseases [S44] (SKIPPED)
  31. Epidemiology of Fungal Disease [S45]
  32. Remember that you have endemic mycoses vs. worldwide mycoses.
  33. Endemic mycoses (Blastomyces - exogenous)
  34. Worldwide mycoses (Candida - endogenous)
  35. In most cases, systemic fungal diseases are transmitted by inhalation of spores in the environment.
  36. Respiratory inhalation
  37. Histoplasma – exogenous mycoses in bird droppings that will cause a calcified granuloma in the lung.
  38. Cutaneous inoculation
  39. Sporothrix – fungus that lives on woody plants, can cause granuloma and skin diseases.
  40. Systemic invasion by opportunists
  41. Candida – causes an oral flush with whitish plaques with yeast in them in the mouth
  42. Suggests they have been on antibiotics (normal flora has been altered) or T cell deficiency.
  1. [SQ3]: Can you still work on a patient with a Candida infection or can you just send them away to another doctor?
  2. [A]: You can get the immediate disease under control by asking whether they have been on antibiotics. If they say no, then you can assume T cell deficiency. You can do whatever dental work you need to do as long as you don’t irritate the plaques. Might also be HIV because something is obviously wrong with their immune system.
  1. Contact with infected hosts
  2. Dermatophytes – only type of fungal infection transmitted person to person.
  3. Can be transmitted from humans to humans or animals to humans.
  1. Fungal Disease [S46]
  2. True Pathogens
  3. Blastomyces & others – even if you are healthy & you inhale this organism you can get respiratory disease that disseminates to your bone and skin.
  4. Opportunists
  5. Histoplasma
  6. Candida
  7. Aspergillus – always shows up as a mold that causes disease.
  8. Cryptococcus – always shows up as a yeast (encapsulated).
  9. Encapsulated Cryptococcus is shown on the slide with India Ink test.
  10. [S47]: Fungal Morphology
  11. Think of bacteria in terms of a yeast (look like bacteria, except larger) or a mold (hyphal forms)
  12. Many fungi will produce molds or yeast.
  13. In some cases, they will be a mold (low temperature) in the environment and a yeast in the body (higher temperature). This switching of morphology is termed “thermal dimorphism” and is shown in Histoplasma and Blastomyces.
  14. In contrast, Aspergillus always shows up as a mold and Cryptococcus is always a yeast.
  15. Aspergillosis [S48]
  16. Slide shows Aspergillus with silver staining branching at an acute angle with septate hyphae.
  17. There are four different ways in which a mold like Aspergillus can produce disease:
  18. Allergic - hypersensitivity to spores.
  19. Colonizing- “Fungus Ball” in the lung, but not invading, just a mass.
  20. Invasive - systemic infection of the lung tissue in debilitated hosts.
  21. Can cause thrombosis and infarctions by invading the blood vessels.
  22. Aflatoxin (A. flavus) – a carcinogenic exotoxin
  23. Can cause severe liver damage.
  24. Histopathological Response to Fungal Infections [S49]
  25. Fungi produce a lot of different types of pathological lesions.
  26. Acute pyogenic abscess that looks like a Staphylococcus (Candida).
  27. Chronic granuloma that will look just like Tuberculosis (Histoplasma).
  28. Chronic, localized dermal infiltration that looks like cellulitis (Dermatophytes).
  29. Mixed pyogenic and granuloma lesions, will see this in one of the case studies (Blastomyces).
  30. Blood vessel invasion with thrombosis & infarction
  31. They grow inside blood vessels and clog them with their hyphae (Mucorand Aspergillus).
  32. Hypersensitivity to spores without tissue reaction, it is all a physiological reaction; a type I reaction IgE reaction to the spores (Aspergillus).
  33. Eukaryotic Parasites [S50]
  34. Last group of organisms that we will discuss.
  35. This slide is of a giardia tropozoite.
  36. How Eukaryotic Parasites Cause Disease in Humans [S51-S54]
  37. How do parasites cause disease? Will answer this question by giving examples.
  38. [S51] – Multiplying in Host Cells
  39. In one case they can kill the host cells by multiplying in them.
  40. Toxoplasma is a protozoan prevalent in people with underlying cell immunity deficiencies.
  41. Carried in cat feces.
  42. Can cross the placenta and cause disease in a developing fetus. This is why pregnant women should not clean out cat boxes.
  43. Very important cause of disease in people with HIV who complain of headaches.
  44. Do a scan of this patient’s brain, and ifyou see masses in the brain it is either Toxoplasma or a lymphoma.
  45. Slide shows someone with Toxoplasma cysts in the brain.
  46. Another thing Toxoplasma (as well as CMV) causes that optometrists should be aware of (especially in HIV patients) is chorioretinitis.
  47. It grows inside host cells, kills them, and produces these lesions.
  1. [S52] – Eat Host Cells
  2. Eat host cells. - Ancylostoma duodenale “Hookworm”
  3. Contracted by invading the skin.
  4. Attach to intestinal mucosa.
  5. Feed on erythrocytes.
  6. Heavy infestation > 1000 worms.
  7. 100 mL/day blood loss (anemia).
  8. Notice the hooks on the slide.
  9. [S53] –Take Up Space
  10. Taenia solium – pork tapeworm
  11. Can get the infection by being the intermediate host or the definitive host depending on whether you ingest the eggs or the tissue that has the worm in it.
  12. You can get cysticercosis if you serve as the intermediate host if you ingest the worm, and can cause a cysticercal cyst in the brain by taking up space.
  13. [S54] – Cause Destructive Immune Response
  14. Induce destructive immune response.
  15. Schistosoma mansoni is the liver fluke.
  16. Not endemic around the U.S. but good example of pathogenic method.
  17. Larva penetratesthe skin when you walk into infected water; they pass into bloodstream and migrate through lungs, get coughed up and get back into the circulation and reach the liver venules.
  18. Eggs deposit in liver venules and the eggs produce a foreign body granuloma & cirrhosis occurs.
  19. Note the Schistosoma egg surrounded by a granuloma on the slide.
  1. Laboratory Diagnosis of Infection: Direct Examination of Fluids/Tissues [S55-S61]
  2. The remainder of the class will involve the discussion of the laboratory diagnosis of infection.
  3. [S55]
  4. One of the most important things you can do in diagnosis is to do a gram stain.
  5. On the slide is the spinal fluid of someone with meningitis. You see neutrophils and gram-negative intracellular cocci. Just by looking at this gram stain you can be sure that this is Neisseria meningitidis.
  6. [S56] - An acid fast stain of the sputum in someone with weight loss and cough may give you the answer ofMycobacterium tuberculosis, then confirm with culture to know exactly which mycobacterium it is.
  7. [S57]
  8. Example of the “oral thrush” (slide 45) on the hard palate.
  9. Take a sample of this and put a 10% solution of KOH on it. If you can see the yeast, you have made the diagnosis by confirming what you see in the mouth.
  10. Confirm it by looking for the organism in the body fluids.
  11. [S58]
  12. If you think someone has a parasitic infection of the intestinal tract, you examine the stool for the parasite’s ova or larva.
  13. Ascaris lumbricoides – round worm that has characteristic eggs (see slide).
  14. Don’t culture parasites, but look for them in the stool.
  15. [S59]
  16. Treponema pallidum – causes syphilis
  17. If you have a genital ulcer you can do a dark field microscopic exam and look for Spirochetes.
  18. [S60]
  19. Looking at tissues with different histological stains can give you clues about the nature of infection.
  20. This is a periodic acid shift stain of a kidney showing Candida infection (see the yeast and pseudohyphae).
  21. [S61]
  22. This slide is of silver stain that stains fungi black showing the Histoplasma capsulatum in lung tissue.
  23. Silver stains are also used for showing Helicobacter in GI biopsies.
  24. Laboratory Diagnosis of Infection: Culture [S62]
  25. In many cases we want to grow a bacteria and depending on what type of bacteria it is, you could possibly grow something like this mucoid lactose-fermenting Klebsiella pneumoniae on MacConkey agar.
  26. Laboratory Diagnosis of Infection: Serology [S63]
  27. Measure antibodies for those pathogens that aren’t easily cultured (Rickettsiae, Hepatitis viruses, Mycoplasma, etc.).
  28. Can use in an ELISA format. Take micro titer plates that have been coated with the antigen of the organism of interest. Add dilutions of the patient’s serum. If antibody is there, the antibody in the serum will attach to the antigen that is on the plate. Wash serum. Antibody remains attached. Add an anti-human antibody linked to a specific enzyme. Add the substrate for the enzyme and then you will get a colored reaction that will tell you whether or not you have antibody there.
  1. Laboratory Diagnosis of Infection: Other Methods [S64-65]
  2. [S64]:
  3. Antigen Detection directly in body fluids (ex: looking for antigen).
  4. Here you don’t even cultivate the organisms, just look for the presence of the antigen.
  5. Histoplasma antigen detection
  6. Aspergillus antigen detection
  7. Legionella antigen detection
  8. Cryptococcus antigen detection
  9. [S65]:
  10. Skin Testing for Delayed Type Hypersensitivity (PPD): Mycobacterium tuberculosis and confirm it with a smear and a culture and an x-ray to see if you really have a lung disease.
  11. Viral Diagnosis [S66]
  12. Historically, we use tissue culture – CMV
  13. If you want to grow a virus, take a cell line that has been shown suitable for growing that particular virus and take the body fluid or tissue that you think has the viral infection, then put it into a centrifuge to make the cells take up the virus, then incubate and stain cells with a fluorescent stain with an antibody for the virus and you can see the viral inclusions.
  14. Serology – Hepatitis, HIV
  15. Polymerase Chain Reaction - used to detect viral infections: Herpes CNS, Viral Load (Hepatitis C, HIV) by quantitating the number of viral entities or nucleic acids in the body.
  16. Histopathology is useful in some cases such as the Cytomegalovirus in the nuclear inclusions. In some cases, just looking at the tissues will show you viral infections.
  17. Laboratory Diagnosis of Infection: Molecular Detection [S67]
  18. Polymerase Chain Reaction is the test of choice for detection of Chlamydia trachomatis in urogenital specimens.
  19. Potential future application for other common infections.

This was an overview of infectious diseases that complements things discussed in Microbiology.

Monday: Lecture on disease of infancy, diseases of childhood, and discussions of laboratory case study reviews.

Review terminology in those.

[end 37 min]