Past Paper Flashcards
(26 cards)
What direction does a guide RNA go?
5’ to 3’
What are the 3 regions of gRNA and briefly explain their function?
anchor region - base pairs with mRNA
information region - guides the insertion/deletion of uridines, typically U
poly-U-tail - helps stabilize the gRNA
Name four enzymes involved in RNA editing?
endonuclease - cleaves the mRNA at mismatch sites
TUTase - adds uridines
3’-5’ exoribonuclease - removes uridines
RNA ligase - re-joins the edited mRNA strand
How does gliotoxin suppress macrophage and neutrophil activity? (2 marks)
-gliotoxin induces apoptosis in macrophages and neutrophils by activating caspase-3 and -9, causing cell death
-gliotoxin also inhibits the NADPH oxidase complex, essential for the oxidative burst, this means neutrophils/macrophages can no longer generate ROS to kill fungi.
Give 5 risk factors for candidemia?
-catheter use
-broad spectrum antibiotic use
-immunosuppression
-neonates and the elderly
-a previous fungal infection
Name 4 symptoms for candidemia
-symptoms are nonspecific and can mimic bacterial sepsis
-Fever unresponsive to antibiotics
-Chills, hypotension, tachycardia
-Sepsis or septic shock
-Organ dysfunction – particularly kidneys, liver, lungs
How does PVL kill neutrophils? (2 marks)
-PVL is a chemokine that kills neutrophils by creating pores in its membrane, causing lysis and cell death.
-when neutrophils burst, they release toxic granules, proteases and reactive oxygen species which cause inflammation, tissue damage and necrosis
Fill in the missing words;
Alpha toxin binds to ______ and forms a ______ pore, causing ______ lysis.
ADAM10, a β-barrel pore, osmotic
Fill in the missing words;
Panton-Valentine Leukocidin binds to _______ receptors on ______, forming an ________ pore leading to rapid neutrophil lysis
complement, neutrophils, octameric
Negative catalase test is most likely?
Streptococcus
Positive coagulase test is most likely?
staphylococcus aureus
Name me 3 pathogens which are lactose fermenters?
-ecoli
-klebsiella
-Enterobacter
Lactose fermenters show up as what colour on a MacConkey agar?
pink
Name 2 pathogens that test positive for indole?
-e.coli
-proteus vulgaris
Name 2 pathogens that test negative for indole?
-klebsiella pneumoniae
-proteus mirabilis
Name 3 pathogens that cannot ferment lactose?
-salmonella
-shigella
-pseudomonas
Name 2 pathogens that can produce H₂S?
-salmonella
-proteus
Name 2 pathogens that cannot produce H₂S?
-Shigella
-E. coli
Name 2 pathogens that are urease positive?
-proteus
-klebsiella
-Gram-negative rod
-Non-lactose fermenter on MacConkey
-Produces black precipitate on TSI agar
-Motile, urease-negative
-Common cause of enteric fever or gastroenteritis
Salmonella enterica
-Gram-positive cocci in chains
-Beta-hemolytic on blood agar
-Catalase-negative
-Sensitive to bacitracin
-Associated with pharyngitis and scarlet fever
Streptococcus Pyrogenes
-Gram-negative rod
-Lactose fermenter → pink colonies on MacConkey
-Indole-positive
-Motile, oxidase-negative
-Common cause of UTIs
Escherichia coil
-Gram-negative rod
-Non-motile, non-lactose fermenter
-H₂S-negative, urease-negative
-Causes bloody diarrhea without fever
-Invades M cells in Peyer’s patches
Shigella
-Large Gram-positive rod
-Non-motile, spore-forming
-Colonies have “ground glass” or medusa head appearance
-Gamma-hemolytic
-Causes cutaneous ulcers and pulmonary infection
Bacillus anthracis
