Lecture 3

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Question 1 of 47

What steps are taken to obtain a pure culture of bacteria? = Take sample (mouth swab, blood sample, urine sample), culture, isolate

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Question 2 of 47

What are diagnostic methods of microbiology?= (5) Structural features, biochemical properties, antibody binding, phage typing, DNA/RNA

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Question 3 of 47

What are some clues for colony identification?= (4) Shape, appearance, colour, odour

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Question 4 of 47

What is the first test in bacteria identification?= Gram staining

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Question 5 of 47

What are the steps for gram staining? =(5) Fixation, crystal violet, iodine treatment, decolorisation, counter stain safranin

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Question 6 of 47

What does fixation do?= Denature some proteins, causing isolate to adhere strongly to slide

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Question 7 of 47

What does crystal violet do?= Binds to peptidoglycan (both in gram +ve and gram -ve)

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Question 8 of 47

What does iodine do?= Crystallises crystal violet to fix it into cell

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Question 9 of 47

What does decolourisation (alcohol/acetone) do?= Decolorises the lesser amount of peptidoglycan in gram negative cell walls, but leaves most of the thicker peptidoglyan layer in gram positive bacteria violet in colour

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Question 10 of 47

What does counterstaining do?= Safranin colours both gram positive and negative pink but because gram positive is already violet, the pink stain is not visible in gram +ve but it is in gram -ve

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Question 11 of 47

What would you identify large, violet, budding, round microbes as after gram staining?= Yeast such as candida albicans

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Question 12 of 47

When do you need to use zie-Neelsen (acid fast) stain?= When gram staining doesn’t work, eg. prevented by wax like coat of mycolic acid on mycobacteria 

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Question 13 of 47

What are the steps to use acid fast mycobacterium? (3)= "Carbolfuchsin, heat (stains mycobacterium)

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Question 14 of 47

Ethanol, HCL (decolourises stain from everything except mycobacterium)

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Question 15 of 47

Ethanol, HCL (decolourises stain from everything except mycobacterium) Methylene blue (counter stain)"

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Question 16 of 47

Are the oranisms that appear red in acid-fast stains gram +ve?= They have gram +ve cell wall morphology but are not gram +ve

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Question 17 of 47

What stain is used for moulds?= Lactophenol cotton blue stain

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Question 18 of 47

What are the steps for staining with lactophenol cotton blue? =(2) Phenol kills mould and prevents lysis, cotton blue stains chitin in cell wall

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Question 19 of 47

What test is used to differentiate between staphylococci and streptococci?= Catalase test

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Question 20 of 47

Are staphylococcus catalse positive or negative?= Positive (bubbles)

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Question 21 of 47

Are streptococci catalase positive or negative?= Negative

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Question 22 of 47

Which test is used to identify staphylococcus aureus?= Coagulase test

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Question 23 of 47

What happens in the coagulase test if s. aureus exists in the sample?= Coagulation of fibrin proteins (caused by surface bound protein of S. aureus)

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Question 24 of 47

What happens in a coagulase test if the sample is of other staphylococci but not S. aureus? No polymerisation (clotting)

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Question 25 of 47

Which test identifies pseudomonas, neisseria, mortadella, campylobacter Oxidase test

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Question 26 of 47

How do microbact strips work?= A strip of independent tests that change colour after bacteria cause bichemical reaction, (eg. some bacteria will ferment glucose creating acid which turns bromothymol blue yellow)

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Question 27 of 47

How does selective agar work?= Contains discs with inhibitors to prevent growth

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Question 28 of 47

How does differential agar work?= Contains discs with indicators to differentiate organisms

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Question 29 of 47

What is sabouraud agar selective for?= (2) Fungi, suppresses bacterial growth

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Question 30 of 47

How is sabouraud agar suppressive against bacterial growth?= Low pH

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Question 31 of 47

What is Eosin-methylen blue agar selective for?= Gram-negative bacteria (toxic for gram +ve, differentiates strong lactose fermenters as green)

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Question 32 of 47

What is MacConkey agar selective for? =Intestinal pathogens (salt inhibits non-enteric bacteria) differentiates lactose fermenters as pink

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Question 33 of 47

What does blood agar differentiate for?= haemolytic reactions (lyse red blood cells and degrade haemoglobin eg beta-hemolysin does both, alpha does both partially and gamma does none) 

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Question 34 of 47

What is mannitol salt agar selective for? =Haloduric bacteria such as staphylococc

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Question 35 of 47

What does mannitol salt differentiate for?= S. aureus ferments mannitol and appears yellow

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Question 36 of 47

What are haloduric bacteria?= Endure salt environment but are not halophiles

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Question 37 of 47

What is bile mescaline agar select for?= Enteric bacteria (inhibits non-enteric bacteria)

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Question 38 of 47

What is the antibiotic susceptibility test?= Agar plate where discs impregnated  with antibiotics reveal whether or not the bacteria is sensitive, intermediate, or resistant to the antibiotic

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Question 39 of 47

Which methods are used for antibody-antigen interaction?= (4) Cell agglutination, latex bead agglutination, western-blot, ELISA

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Question 40 of 47

How do cell agglutination serotyping work?= Cells clump together in the presence of an antigen eg. O-antigen for E. coli

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Question 41 of 47

How does latex bead agglutination work?= Antibodies bound to latex bead and leads to visible clumping as antibodies bind to antigens of bacteria

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Question 42 of 47

What are the steps to western-blot?= (5) Protein separation by gel, immobilisation by blotting onto membrane, washed (binding) with primary antibody, washed with secondary antibody with label (antibody-antibody binding), substrate added with visible result for specific proteins (conversion of substrate)

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Question 43 of 47

What is an ELISA plate?= Enzyme-linked immunosorbent assay (similar to western blot but is in solution instead of on membrane. easier to quantify protein)

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Question 44 of 47

What is immunoflourescence microscopy?= Similar to western blot but secondary antibody labelled with flourophore which is detected with a flouresence microscope

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Question 45 of 47

How does restriction fragment length polymorphism work?= DNAase cleaves specific DNA sequence if present. Appears as two bands in electrophoresis

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Question 46 of 47

How do polymerase chain reactions work?= Amplifies small amounts of DNA by splitting and cloning DNA strands

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Question 47 of 47

What is a FISH assay?= Flourescence in situ hybridisation. Uses flourescent probes specific to DNA or RNA sequences

Question 47 of 47