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Micro > Lab Midterm > Flashcards

Lab Midterm Flashcards

1
Q

What is total magnification

A

Ocular times objective lens

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2
Q

What is field of view

A

The part of the sample that you are able to see
As magnification or power increases the field of vision decreases

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3
Q

What is depth of field

A

The depth level
Like the strings in top of each other and being able to focus above or below them

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4
Q

What is the working distance

A

Distance between the objective lens and the specimen
Decreases when the magnification or power decreases

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5
Q

What is oil immersion and why do we use it

A

Light doesn’t bend with oil so it gives a better image

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6
Q

What is a defined vs complex mixture, compare them

A

Defined is knowing the exact measurements of each ingredient
Complex is the big mixture that does not have exact numbers

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7
Q

What are two reasons to heat fix

A

Kill bacteria
Adhere them to the slide

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8
Q

What is the difference between negative and simple staining

A

In a negative stain you stain the background and don’t heat fix because that would cause problems with the cell structure
Simple staining you will heat fix and stain the bacteria

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9
Q

What three stains did we do in lab 3

A

Gram stain, endospores, capsule

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10
Q

What is the difference between simple and differential in staining

A

Simple looks at morphology and arrangement
Differential is able to differentiate between types of cells and cell structures such as gram - or + and can see if capsules or spores are present

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11
Q

Why don’t you skip any steps in gram staining and what is the difference in cell wall shape and arrangement in gram stain

A

Decolonizing step is most important because 15 seconds is just long enough to pull the CV out of the gram negative peptidoglycan layer but keep the color in the thick layer of gram positive. If time is too short the CV may stay in the layer of gram - and cause issues when trying to differentiate. If too long the color could be pulled out of both layers which can cause incorrect results as well

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12
Q

Come back to endospore and capsule of lab 3

A

I don’t know what the fuck us going on

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13
Q

How do you calculate prevalence

A

Number of cases/ number of persons

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14
Q

What is the meaning of the correlation statistic

A

The closer the number is to one the more correlation is between the two variables
If the number is closer to zero the variables are not correlated very closely
If the number is negative with high correlation this means as one goes in positive direction the other goes in negative direction but at the same time
Positive number means they both either go up or down at the same time

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15
Q

What are the standard vaccines in the U.S (these are what we should know and not pick because she asked to choose which are not core)

A

Tdap which is tetanus, diphtheria, and pertussis
Rhotovirus
Measles, mumps, rubella
Pneumococcal
Haemophilus influenza
Chicken pox and hep A and B
Polio, varicella, and meningococcal

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16
Q

What is macconkey selective and differential for

A

Selective for gram -
Differential you can tell which bacteria can break down lactose and which cannot

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17
Q

What is sulfide in a SIM test

A

Black is positive meaning H2S is present and clear is negative

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18
Q

What is motility in a SIM test

A

If there is a line it’s motility negative because it shows the bacteria didn’t move
If the bacteria is spread out in the tube it’s motility positive

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19
Q

What is the indicator rxn in a SIM

A

Iron is in the medium which reacts with H2S gas to form iron sulfide

20
Q

What is the putrefaction rxn

A

When cysteine is converted into pyruvate using cysteine desulfarase and H2S is a by product
This is only one of the ways H2S is made

21
Q

Besides putrefaction what is another way H2S is made

A

Anaerobic respiration which is when thiosulfate is reduced or picks of electrons and becomes a gas

22
Q

True or false: SIM cannot tell us which of the two rxns made the H2S present in the test it just tells us its present

A

True

23
Q

What are the results of a blood agar hemolysis

A

Alpha means partial breakdown of red blood cells using enzymes
Beta is full breakdown
Gamma is no breakdown

24
Q

How does a catalase test work (keep it simple)

A

Breaks down hydrogen peroxide to water and oxygen and the oxygen is why we see bubbles
Positive test is bubbles and negative is no bubbles

25
Q

What is aerobic catalase

A

When the bacteria need oxygen so they will have both SOD and catalase, bubbles will be present and they will survive at the to of the tube

26
Q

What is facultative in a catalase test

A

Prefer to have more oxygen for energy but can live without it so you have positive SOD and catalase
You will find them at the top and also dispersed throughout the tube

27
Q

What are anerobes in a catalase test

A

Don’t use oxygen but don’t hate it they only kill the worst of oxygen
Have SOD but not catalase and they are found throughout the tube

28
Q

What are obligate anaerobes in a catalase test

A

Don’t like oxygen at all so they are both SOD and catalase negative
They love far away from oxygen as possible so they are found at bottom of tube

29
Q

What are microaerophiles in a catalase test

A

Only live in 2-10 percent oxygen
Have SOD and only some have catalase
Live almost at the top of the tube

30
Q

What are the important parts of an Elisa and what is the importance of each step

A

Each sample has proteins that will bind to the well
Specific antibodies will seek out specific antigens that are bound to the well
Wash after every step to remove unbound primary and secondary antibodies, this step prevents false positives from occurring
Secondary antibodies Are added and will bind to primary antibodies, wash after this to wash away unbound antibodies
Enzyme is added that chemically changes changes the enzyme substrate turning it from colorless to blue
False negative could occur if antibody has low specificity or affinity for target antigen
Low concentration if antigen may also cause problems when binding to antibody

31
Q

What is an indole test

A

Tryptophanase breaks down tryptophan into indole, ammonia, and pyruvate
If positive it will have red ring and if negative ring will be clear
Some rxns test rxn with kovacs reagent because when it mixes with indole it turns red

32
Q

What is the methyl red test

A

Ph indicator that turns red if acid fermentation has occurred and remains yellow is pH is greater than 6.2
Positive when color is red and negative when color is yellow or clear

33
Q

What is VP test

A

Used to detect microorganisms that ferment glucose via the butanedoil pathway
Positive means red color and pale yellow is negative

34
Q

What is the citrate test

A

Determines organisms ability to use citrate as sole carbon source
Green is negative and blue is positive

35
Q

What is a casein test

A

Caseinase is an Extracellular enzyme that breaks down casein
Put bacteria on skim milk agar plate and if there is a clear ring around the colony this means they can break down casein and result is positive
Negative is when there is no ring

36
Q

What is the starch test that uses alpha amylase

A

Alpha amylase is an enzyme that is secreted by some bacteria to break down starch
It’s a polymer of glucose, it’s huge, and needs to be broken down to fit into the cell
Put iodine on starch plate and if there is clearing around the colony it means positive result, no clearing stays blue and there is no starch breakdown so no alpha amylase present

37
Q

What is the zone of inhibition

A

Clearing around the antibiotics where bacteria is either dead or inhibited
Measured in mm and just by looking at it you cannot determine if bacteria are dead or inhibited so you must take a swab and grow on separate agar, if they grow the bacteria were just inhibited and not dead

38
Q

What can be determines from a Kirby Bauer test

A

Determines antibiotic susceptibility for bacteria and allows practitioners to know which antibiotics should be used to treat infection
Agar used is mueller Hinton and is non selective so it will not inhibit sulfonamides
Based on criteria they can either be resistant, intermediate, or susceptible

39
Q

What is the phenol coefficient

A

Divide chemical agent dilution by phenol dilution factor
This tells how many more times the chemical agent is more effective than the phenol
Calculated my comparing concentration that will kill all microorganisms after ten minutes but not five minutes

40
Q

What is a spread plate and how do you use it

A

Pipet onto agar plate and use spreader to spread the bacteria evenly, lawn of growth should be observed
In order to quantify you should know how much you pipet onto the plate and observe thickness of the growth

41
Q

What is a streak plate and what is the dilution technique

A

Streak the plate with bacteria then sterilize, then streak the plate again using the colony you just put on the plate, sterilize again and streak the plate with the second colony you added to the plate
This will create different colonial morphologies

42
Q

What is EMB and what is it defective and differential for

A

Eosin methylene blue
Selective for gram negative because it contains methylene blue and bile salts
Differential for acid production from lactose breakdown
Neon green metallic color means high production but could also observe pink metallic

43
Q

What is an MSA plate and what is it selective and differential for

A

Mannitol salt agar plate
It is selective for gram positive and contains 7.5 % salt
Differential for mannitol sugar fermentation which results in color change, there is a ph indicator present so color will change from pink to yellow if present

44
Q

How do we know if a slide contains an endospore and what stain do we use

A

Differential stain for spore forming bacteria
You will see green spore with a pink layer surrounding it
You must steam malachite green stain into the spore in order to see it

45
Q

How do you stain a capsule

A

Use copper sulfate
It will appear as colorless halo around bacterial cell but the cell itself will be pink and background will be dark stain
Don’t heat fix as this can compromise the structure

Micro (8 decks)

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