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Microbio. (MEDI2003) > Practical > Flashcards

Practical Flashcards

1
Q

Why can’t you use a swab in a transport media for gram stain?

A
  • Low no. of cells for accurate gram stain result
  • Gelatinous material from media = poor stain
  • Not represent actual environment cells were taken from
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2
Q

Why is it important to have a purity plate when performing tests?

A

confirm that only one organism is tested & the results given are due to that one organism

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3
Q

Why don’t we measure the zone of clearing produced from a bacitracin test?

A
  • Bacitracin disk is uncalibrated

- Measuring the zone of clearing is not important as any zone of clearing = a susceptible result (or resistant if none)

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4
Q

How can phage susceptibility be used?

A
  • phage can infect certain strain of bacteria
  • Can use Phage profiling to see if infected patients have same bacteria
  • see which phage can infect the bacteria isolate
  • & trace where it came from
    = can help stop the spread of disease once know the original patient/location
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5
Q

Why can you keep the same pipette when working from hi dilution to lo dilution?

A
  • when work from Lo -> Hi [ ] can’t carry high [ ]: Lo [ ] doesn’t change concentration of Hi [ ]
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6
Q

Describe the test used to detect lecithinase

A
  1. Nagler (egg yolk) plate - pale
  2. if lecithinase produced = FA tails & glycerol heads of phospholipid split
  3. = zone of white precip. (FA deposit) around colonies = +ve result
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7
Q

List benefit/s of lecithinase during an infection

A

-Separates glycerol heads & FA tails
= breaks phospholipid = cells & WBC lyse
= access nutrients & evade immune system

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8
Q

Describe the test used to detect DNAse

A
  1. methyl green dye is bound to DNA - green
  2. If DNAase is produced= methyl group is cleaved from DNA (making it soluble- nucleotides)
  3. yellow/clear zone of clearing around inoculate = +ve result
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9
Q

List benefit/s of DNAse during an infection

A

DNAse = breaks DNA = viscous/runny/slimy = help in motility = move around body

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10
Q

Describe the test used to detect catalase

A
  1. H2O2 -> O2 + H2O
  2. If catalase produced = rapidly breaks down H2O2
  3. = O2 gas is produced = see bubbling/fizzing = +ve result
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11
Q

List benefit/s of catalase during an infection

A

catalase = protects from lethal effects of O2 (ie. reactive O2 sp.) = prevents the bacteria from being killed

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12
Q

Describe the test used to detect oxidase

A
  1. Filter paper soaked in TMPD (dried oxidase reagent- an e- donor)
  2. The presence of Cytochrome C oxidase (e- acceptor)
  3. TMPD lose e- (i.e.oxidised) => blue/purple colour (indole phenol) = +ve result
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13
Q

List benefit/s of oxidase during an infection

A

oxidase accepts e- for e- transport & metabolic pathways of bacteria= bact. survive

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14
Q

Describe the test used to detect coagulase

A
  1. Fibrinogen in plasma
  2. If coagulase on C.wall = forms fibrin clot (from fibrinogen) around bacteria
  3. = White clumps =+ve result
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15
Q

List benefit/s of coagulase during an infection

A

Coagulase forms fibrin clot from fibrinogen = surround bacteria & cover receptors = protect bacteria from phagocytosis

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16
Q

Describe the test used to detect haemolysin

A
  1. BA = RBC - red plate
  2. if produce haemolysin
  3. => clear/partial zone around colonies = lysed RBC= +ve result
17
Q

List benefit/s of haemolysin during an infection

A

Haemolysin = lyse RBC & leukocytes = access to nutrients & evade immune system

18
Q

Describe the test used to detect protease

A
  1. Caesin agar (insoluble protein in milk) - white plate
  2. If produce protease = break down protein
  3. => clear zone around colony = +ve result
19
Q

List benefit/s of protease during an infection

A

Protease = breakdown proteins like antibodies into AA = protect from host defences

20
Q

Role of peg

A

Removes water from glycocalyx to allow hydrophobic interactions bw cells= contact= conjugation

21
Q

Why is haemophilus a causative agent after prelimary testing for pattys droolingn?

A
  • facultative anaerobe (grew w/ & w/out O2)
  • grew in CHOC not in BA (= fastidious)
  • causes respiratory infections
  • GNB
22
Q

What are x & V factors and their roles?

A

X: Haemin> iron in harmoglobin
Y: NADH/NAD+> e- transport chain

23
Q

Why are choc plates incubated in co2?

A
  • Grows fastidious organisms that are usually capnophillic

- replicate environment in lungs bc specimen came from lungs= rich in co2

24
Q

Role of protein A as virulence factor

A

Prevents detection & engulfed from phagocytes bc protein A blood nds to fc portion of antibody = can’t bind to receptor on macrophages

25
Q

What are the no. that indicate consistent e UTI

A

Colonies: >200 or >10^8 cfu/mL
WCC: >100 x 10^6 WBC/L

Microbio. (MEDI2003) (16 decks)

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