BMS1064 - Practical Qs Flashcards
(26 cards)
What does MRD stand for?
Measurable residial disease?
Why do we use MRD?
What is a stomacher and how does it work?
A paddle blender used to homogenisze solid samples in liquid media.
Operated by massaging the sample in a sterile bag - breaking down the material without direct contact between the sample and the machine.
How would you prepare a decimal dilution series to 10^-5 starting with 10^-1 dilution.
Take 10um of liquid and add it to 90um water. Shake. Repeat 3 times.
Why do we prepare a dilution series?
So we can have a dilute enough sample to count bacteria colonies.
What is PCA?
What is a spread plate? How do you use it?
What does c.f.u. / ml mean?
Colony forming unit / ml
How many bacterial colonies grow per ml of liquid
Why do we incubate petri dishes upside down?
Briefly describe how you would calculate c.f.u./ml or per gram of a sample.
Describe how one produces a smear of bacteria on a slide.
Describe the process of performing the gram stain.
What colour are gram pos and neg bacteria?
Gram pos = purple
Gram neg = pink
What does punctiform mean in terms of colony appearance?
Tiny colonies
Why do we view microorganisms with a microscope using immersion oil?
To reduce refraction - so we can see the image clearer
Describe the oxidase test
Hydrate oxidase reagent (crystals) with distilled water. Dip a swab into oxidase reagent solution and dab a colony of bacteria with swab.
Pos result: purple colour appears in 20s - oxidase enzyme present
Neg result: no purple colour appears in 20s
Describe the catalase test
Dispense a drop of hydrogen peroxide into empty petri dish. Using a steralised inocculating loop, mix bacterial colongy with hydrogen peroxide.
Pos result: effervesence within a few seconds - catalase enzyme present.
Neg result: no effervence within few seconds
NOTE: these tests (catalase and oxidase) may appear to show positive result after a longer period of time (false positives)
Why are catalse and oxidase test useful?
Helpful to identify type of bacteria present. Some bacteria do/don’t have these enzymes.
What kind of bacteria would you expect in Yakult? Gram pos or neg? What agar do these bacteria grow best on?
Gram positive (lactobacilli)
Grows on MRS agar.
How would you determine the number of bacteria in Yakult?
Make a series of dilutions and grow on plates. Count bacterial colonies which form.
What bacteria would you expect to see in Roquefort cheese? Name another blue cheese that contains this mould.
Penecillium roqueforti
Stilton
What is kefir? What are the role of microorganisms in it?
Fermented dairy product with bacteria and yeast …
What kind of stain is used to view moulds under the microscope?
Methylene blue solution
What does MEA stand for?
Malt Extract Agar
