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64 Cards in this Set

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