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64 Cards in this Set
- Front
- Back
What do microorganisms use to bind to host receptors?
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adhesins
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What do fimbrial adhesins interact with?
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epithelial glycolipids
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What do some gram- bacteria have their adhesins attached to?
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fimbraie or pili
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What adhesin is located directly on the cell and interacts with integrins?
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invasin
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Gram+ bacteria attach to mucosal cells using?
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fibronectin
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What happens in very ill hospitalized patients in terms of the mouth flora? What illness in turn tends to be high in these patients?
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they have less fibronectin meaning there are fewer gram+ bacteria and more gram-. gram- take over and cause pneumonia.
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What organism is commonly found on plastic catheters
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staph. epidermidis
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When a large number of bacteria enter the body what happens to the concentration of iron?
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Free iron is already low but further decreases becuase host cells release more iron binding proteins.
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Why are streptococci adept at growing in the mouth?
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They have the ability to use sucrose.
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What represses complement from being activated on host cells?
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sialic acid on the plasma membrane
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What organism adds sialic acid to the terminal sugar of LPS?
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gonococci
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How does meningococci prevent complement activation?
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by binding the Fc portion of the IgA antibody to its capsule
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How does herpes avoid activating complement cascade?
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by binding to C3b with a glycoprotein in its envelope
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Which activation pathways of the complement cascade does herpes prevent?
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alternative pathway
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what does vaccinia virus secrete to prevent complement activation?
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C4bp which binds to the C4b fragment
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Which complement pathway does C4bp work through?
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classical pathway- it prevents C4b from activating C3
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How salmonella and e. coli prevent complement? Which strain evades complement?
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The smooth strain has long O-antigen polysaccharides that prevent the MAC from reaching the membrane. Rough strains do not have little to no O antigen
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What gram+ has a capsule?
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staphyloccocus
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What organism directly inhibits neutraphil chemotaxis and motility? How?
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Bordetella pertusis makes a toxin that inhibits cAMP.
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What organisms inactivate C5a?
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streptococcus has a C5a peptidase and psuedomonas aeruginosa
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Several bacteria make leukocidins that directly kill neutrophils and macrophages. What are a few?
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highly invasive bacteria like pseudomonads, staphylococci, group A streptococci and clostridia
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Streptococci and staphylococci make proteins that reduce opsonization. What is the molecule?
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protein A that binds IgG at the Fc portion
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How does L. monocytogenes escape the phagosome?
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It produces listeriolysin which weakens the membrane of the phagosome
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What pathways does Legionella inhibit in hosts?
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hexosemonophosphate and oxygen consumption in neutraphils decreasing respiratory bursts
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On a biopsy you find syncytia. What viruses do suspect?
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HSV, varicella zoster, and respiratory syncytial virus. Note syncytia = multinucleate giant cells
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Which bacteria are capable of migrating through cells using the cells cytoskeleton?
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Shigella and L. monocytogenes
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On microscopic exam fingerlike projections are observed at one end of a cell. Bacteria appear to occupy the area. What could the infection be?
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Shigella or L. monocytogenes
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What viruses in addition to HIV cause immunosuppression?
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measles, influenza, HBV
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A person infected with what viruses may make someone more susceptible to tuberculosis or an opportunistic infection?
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HBV, influenza, measles
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How do microbes avoid being phagocytosed by diversion?
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inactivate complement C5a, leucoaggregation, and pulmonary sequestration
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How do microbes "play hard to get" to avoid being phagocytosed?
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They have a slimy capsule on the organism. They have M protein, or they have pili.
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What is the mechanism of humiliation that microbes use to evade phagocytosis?
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release adenylate cyclase, leading to high levels of cyclic adenosine monophosphate, all phagocyte functions depressed
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How do microbes use paralysis to avoid phagocytosis?
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make cells unresponsive to chemotactic factors, induce inhibitors of migration, or inactivate chemotaxins (C5a).
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Which organisms use leucoaggregation and pulmonary sequestration to avoid being phagocytized?
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Gram- enterics
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Which organisms have a slimy capsule that helps them avoid phagocytosis?
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pneumococci, meningococci, haemophilus influenzae, bacteroides fragilis and more
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Which organism uses an M protein that helps them avoid phagocytosis?
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group A strep
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Which organism releases adenylate cyclase that helps them avoid phagocytosis?
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Bordetella pertusis
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Which organism uses a pilus to avoid phagocytosis?
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gonococci
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Which organisms make immune cells unresponsive to chemotatic factors enabling them avoid phagocytosis?
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capnocytophaga, tubercle bacilli
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Which organism produces inhibitors of immune cell migration that helps them avoid phagocytosis?
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leprosy bacilli
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Once phagocytized what bacteria cause membrane lysis and "murder"?
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Streptococci (streptolysin O and S)
Pseudomonas (exotoxin A) Staph a. (alpha toxin) |
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What bacteria are indifferent to the lysosomal enzymes?
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Salmonella enterica, mycobacteria, and Leishmania (protection by surface lipophosphoglycan)
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Which bacteria can disable or inhibit phagosome-lysosome fusion?
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Tubercle bacilli, Legionella pneumophila (redirect phagosomal trafficking), Toxoplasma gondii (remove host proteins from the phagosomal membrane)
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Which bacteria can disable by inhibiting oxidative killing?
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virulent salmonellae can inhibit the respiratory burst
Legionella pneumphila, Listeria monocytogenes and staph a. all contain catalase |
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Which organisms have the ability to escape the phagosme?
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L. monocytogenes, shigella, rickettsiae, and influenza viruses
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What is the purpose of superantigens? Which organism secretes them?
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to activate and confuse the immune system with many different unrelated streptococci antigens generating a non-specific T cell response. Streptococci
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Where do superantigens bind on the TCR?
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It does not bind in the antigen binding groove but binds outside of it on the Vbeta domain. Each superantigen binds preferentially to one Vbeta type and activates that T cell
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What two receptors do superantigens bind on the T cell?
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the MHC and the Vbeta domain of the TCR does not bind either in the antigen binding pocket
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What type of organism is trypanosoma brucei and what does it cause?
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They are a protozoa that causes sleeping sickness infecting blood and interstitial fluid
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What is unique about trypanosoma brucei? What does this lead to?
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The have a variable surface glycoprotein that changes and as a result people are prone to relapsing infections
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Which gram- can change its pilin periodically?
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gonococci
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What bacteria shares the same antigenic variation as trypanosoma brucei?
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borreliae
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What is different about the antigenic variation seen in influenza as compared to borrelia and trypanosoma?
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influenza does not change its antigens within individual hosts and cause relapsing infections
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What process accounts for minor antigenic changes in an organism like influenza? What time span does this occur in?
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antigenic drift which occurs over 2-3 years
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Major changes in an organisms antigens is the result of what and what is the time interval for this to occur?
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antigenic shift occurs every 10 years or so
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With antigenic shift what molecules on influenza virus will change?
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hemagglutinin- binds to surface receptors
neruaminadase- changes host cell receptors? |
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Which bacteria have the ability to cleave IgA at the hinge region to yield ineffective fragments?
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gonococci, meningococci, and haemophilus influenzae
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What is the function of staphlokinase?
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it is a serine protease that cleaves host plasminogen to plasmin to dissolve clots and also degrades IgG and C3b.
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Name an organism that has the capacity to avoid both opsonization and phagocytosis?
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staph a. via staphlokinase
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What is fabulation?
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The ability of a baceria to degrade IgA and bind the Fab fragment making their antigens unavailable to the host
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How does herpes spread once in the host?
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through cytoplasmic bridges between cells
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Which of the host defenses can affect a latent virus?
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none
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In general do have environmentally tough transit forms?
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No but chlamydiae does
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How is yersinia pestis spread?
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From human to a flea. It replicates in the fleas digestive tract causing blockage making the flea feel hungry. The flee then feeds excessively infecting more people
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