MIMM 413 Lecture : jan 23 2012- dr. matlashewski.docx
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When someone gets a bone marrow transplant, they have to be quarantined and carefully protected from pathogens for a period of time afterward. Why?
| A. | Bone marrow produces the main cells involved in the specific immune response, so these patients are at special risk of infection until they build up enough marrow to produce sufficient cells. | |
| B. | Bone marrow produces blood cells, so they have insufficient circulation for a period of time so their immune system lacks the energy to fight off any infection. | |
| C. | Anytime a foreign substance, even someone else's bone marrow, is introduced to a body, there is an extra risk of infection. | |
| D. | A common complication of bone marrow transplants is infection, and doctor's don't want the infection to spread to others. | |
| E. | It's a traumatic procedure, and any extra stress on their body could kill them. |
There is antibody-mediated and cell-mediated specific immunity. Which type of cells are primarily involved in the antibody-mediated immune response?
| A. | Macrophages | |
| B. | B cells | |
| C. | Complement proteins | |
| D. | T cells | |
| E. | Antigens |
From the bacteria's perspective, why is it helpful that it produce diarrhea in people?
| A. | Because it gets the bacteria out of the person and, likely, into the next one | |
| B. | It's not helpful really. That's just what that toxin causes. | |
| C. | Because that quickly kills the person | |
| D. | Because it makes the patient too unpleasant to be around | |
| E. | Because there is no real treatment for that |
Where do prions come from?
| A. | There are prion-like particles in the brain normally, and when these become abnormal they can cause disease. | |
| B. | Mosquitoes. | |
| C. | They are clumps which form from normal prion-like particles in the blood that travel to the brain. | |
| D. | They are introduced by infectious protozoa. | |
| E. | Contaminated water. |
QUESTION 1: The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by __________________________.
| A. the helical shape of its viral capsid |
| B. the type of nucleic acid used for its viral genome (single-stranded, antisense RNA) |
| C. the spikes that protrude from its viral envelope |
| D. the segmented nature of its viral genome |
QUESTION 2: Which of the following genome types has been observed in viruses? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.
| A. Single-stranded RNA |
| B. Single-stranded DNA |
| C. Double-stranded RNA |
| D. Protein-based |
QUESTION 3: Choose the correct statement about viral evolution.
| A. RNA and DNA viral genomes evolve at equal rates. | ||||||||||||
| B. Cellular genomes mutate at a faster rate than viral genomes due to their large size and increased chance of replicative mistakes. | ||||||||||||
| C. DNA viruses mutate faster than RNA viruses because thymine is more susceptible to mutation than uracil. | ||||||||||||
| D. RNA viruses mutate faster than DNA viruses due to a lack of proofreading replicative enzymes. QUESTION 4: Your elderly patient is affected by shingles. After careful observation, you note that the virus responsible for the infection has an icosahedral capsid, is enveloped, and has double-stranded linear DNA as its genetic material. Based on this information, in which of the following viral families would you group this viral pathogen?
QUESTION 5: Which of the following is a key difference between lytic and lysogenic bacteriophage replication cycles?
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A 47 year old female patient presents herself to you with symptoms of pneumonia. All indications are that the patient is suffering from an infection of Streptococcus pneumoniae, a Gram-positive bacterium. Since the patient is not allergic to penicillin, you prescribe a dose of amoxicillin, a semi-synthetic penicillin. This drug works by blocking the peptide cross-links, between the muramic acid subunits, of peptidoglycan chains. This leads to a destabilization of the bacterial cell, leading to its rupture.
However, after the patient finished her course of amoxicillin, no improvement in symptoms were reported. Perplexed, you decide to culture and examine the bacteria infecting her lungs. The test you order is a Gram stain test, which comes back as Gram-negative. You feel like a failure as a health care provider due to your misdiagnosis of this bacterium.
The same day, you put the patient on an aminoglycoside class antibiotic. This antibiotic is Gram-negative specific and works by shutting down ribosomes. You are dismayed and confused when this treatment also fails.
To get a full read on the disease, you have a barcoding DNA test done on the causative bacterium. The test comes back and it clearly shows that the bacterium is within the group of Gram-positive bacteria. With the results of this test, you come up with the theory that the patient is infected with a strain of Drug Resistant Streptococcus pneumoniae (DRSP), resistant to amoxicillin. You decide to treat the DRSP by administering intravenous vancomycin, which is indicated for the treatment of serious, life-threatening infections by Gram-positive bacteria. This treatment also fails.
In the end, you figure out that you were wrong about everything, and that there was a simple solution to the treatment of the patient.
Now knowing that the patient was infected with Mycoplasma pneumoniae, what is the likely explanation for the false Gram-negative test?
Before you answer this question you may want to know how Gram staining works. Briefly, the Gram stain is a differential stain meaning that you are using two dyes that stain different structures. Based on the structural differences of the bacteria, the dyes will interact differently with them, producing different results (colors). The Gram stain (Crystal Violet together with Gram's iodine) stains thick layers of peptidoglycan purple and thin layers of peptidoglycan very, very lightly purple. The second stain (or counterstain) is safranin. Safranin is a dye which interacts with and binds to lipid bilayers. Yes, safranin also stains the cytoplasmic membrane of Gram-positive bacteria, but the deep purple color of the Gram stain makes it impossible to see.
| A. | The Gram stain was able to penetrate the cell making it turn pink | |
| B. | The counterstain stained the cytoplasmic membrane, making it look like a Gram-negative bacterium | |
| C. | The counterstain stained the mycolic acid in the cellular envelope, thus making it look like a Gram-negative bacterium | |
| D. | The Gram stain lightly stained the present peptidoglycan (making it look pink rather than red). |
