Lab Final Cumilative Content Flashcards
(153 cards)
1
Q
Differential stains allow a microbiologist to:
3-7: Gram Stain
A
Differentiate bacteria based on qualities such as gram (+) and gram (-) bacteria
2
Q
Which are used more frequently, differential stains or simple stains?
3-7: Gram Stain
A
Differential Stains are used 95% of the time
3
Q
The most commonly used differential stain in bacteriology is the _______________ stain.
3-7: Gram Stain
A
Gram
4
Q
Besides the gram stain, other differential stains test for the presence of _____________, _____________, _________________, or __________________ in bacteria.
3-7: Gram Stain
A
- Acid-fastness
- Capsule
- Spores
- Flagella
5
Q
In the gram stain a _____________________ step occurs between the application of two ___________ stains.
3-7: Gram Stain
A
- Decolorization
- Basic
6
Q
The primary stain in the gram stain is _____________________. What do bacterial cells look like after application of this primary stain?
3-7: Gram Stain
A
- Crystal violet
- Purple
7
Q
Iodine acts as a ___________________ in the gram stain. What is the purpose of adding iodine?
3-7: Gram Stain
A
- Mordant
- Binds negative charge to positive charge of crystal violet allowing more purple to stay on the cells
8
Q
The most critical step in the gram stain is the ______________________ step.
3-7: Gram Stain
A
Decolorization
9
Q
The decolorizing solution we use in the gram stain is _______________________________.
3-7: Gram Stain
A
Acetone Alcohol
10
Q
In the last step in the gram stain, gram negative cells are colored by safranin, which is a ____________________________.
3-7: Gram Stain
A
Red counterstain
11
Q
The ability to resist or not resist decolorization in the gram stain is based on:
3-7: Gram Stain
A
Composition of the cell wall in Gram positive and Gram negative cells
12
Q
What do gram negative and gram positive cells look like before crystal violet is added in the gram stain?
3-7: Gram Stain
A
They are transparent
13
Q
What do gram negative and gram positive cells look like after the mordant is added in the gram stain?
3-7: Gram Stain
A
- Gram positive cells will look purple
- Gram negative cells will be red
- Over exposure results in redish gram positive cells
- Underexposure results in purple gram negative cells
14
Q
What do gram negative cells look like after the decolorization step in the gram stain? Why?
3-7: Gram Stain
A
They will appear transleucent because both the crystal violet and iodine will have been washed off.
15
Q
What do gram positive cells look like after the decolorization step in the gram stain? Why?
3-7: Gram Stain
A
They will look purple because the crystal violet and iodine would have stained the cells and remained attached after the wash.
16
Q
What will happen to gram negative cells if you don’t add enough alcohol in the gram stain?
3-7: Gram Stain
A
They will maintain a red hue from the iodine
17
Q
What will happen to gram positive cells if you add too much alcohol in the gram stain?
3-7: Gram Stain
A
The gram positive cells will become more red in addition to purple giving poor visibility
3-7: Gram Stain
18
Q
Why is it best to use cultures that are 24 hours old or less for gram staining?
3-7: Gram Stain
A
Bacillus and Staphylococcus can lose the crystal violet-iodine complex in more than 24 hours
3-7: Gram Stain
19
Q
Name 3 Gram negative bacterial genera and 2 Gram positive bacterial genera other than the genera used in this exp.
3-7: Gram Stain
A
Gram Negative:
- Eschericha coli
- Citrobacter freundii
- Klebsiella pneumoniae
Gram Positive:
- Staphylococcus aureus
- Streptococcus pyogenes
20
Q
What do the gram negative cells look like after successful completion of the gram stain? Gram positive cells?
3-7: Gram Stain
A
- Gram positive cells will be purple
- Gram negative cells will be pink
21
Q
Why are you asked to gram stain a mixture of gram positive and gram negative bacteria on the same slide?
3-7: Gram Stain
A
To create clear contrast between gram positive and gram negative bacteria
22
Q
Why do you need a counterstain in the gram stain?
3-7: Gram Stain
A
- Crystal violet attaches to both gram positive and negative cells
- Mordant fixes crystal violet onto gram positive cells
- Acetone alcohol Washes the crystal violet off gram negative cells
- Saffranin is then used to stain gram negative cells to provide visual contrast as the gram positive cells remain purple while the gram positive cells become pink
23
Q
Why do gram-negative bacteria stain differently than gram-positive bacteria in the gram stain? Be specific!
3-7: Gram Stain
A
Gram Positive:
- Thick Peptidoglycan layer
- Crystal violet is retained by PG layer with the help of mordant even after acetone alcohol wash
Gram Negative:
- Thin Peptidoglycan layer
- Lipid A dense layer
- Crystal violet is washed out by acteone alcohol due to thinner PG and Lipid A layer
- Safranin is then used to stain the transparent gram negative cells
24
Q
What are teichoic acids?
3-7 Gram Stain
A
- Unique to gram positive bacteria
- Teichoic acids are supporting structures embedded in the PG layer of gram positive bacteria
25
What is the purpose of conducting an endospore stain?
## Footnote
3-10 Endospore Stain
- Allows visualization of endospores
- Allows us to differentiate between spore forming cells and non-spore forming cells
26
What two bacteria produce endospores? Are these gram +/-?
## Footnote
3-10 Endospore Stain
- Bacillus and Claustridium
- Gram positive
27
Outline the steps in the cycle of a spore encountering unfavorable then favorable conditions.
## Footnote
3-10 Endospore Stain
1. Mother cell is active
2. Harsh conditions promote sporulation
3. Endospore forms within mother cell and is protected (can survive millions of years
4. Spore encounters favorable germination conditions leading it to become a mother cell
28
What is an endospore and what is it made of?
## Footnote
3-10 Endospore Stain
- Bacterial species that can differentiate into dormant cell when it encounters harsh conditions
- Endospores have a thick protective keratin coat that makes them very tough
29
Why are endospores resistant to heat and chemicals?(3)
## Footnote
3-10 Endospore Stain
- Protective keratin layer
- Dehydrated state
- DNA protective proteins
30
Why must extreme measures be taken to stain endospores?
## Footnote
3-10 Endospore Stain
Because the keratin coat resists staining. Therefore spores must be steamed to soften and allow malachite green to enter
31
What is the difference between an endospore and a vegetative cell?
## Footnote
3-10 Endospore Stain
Endospores - metabolically dormant cell absent of ATP or any metabolic processes
Vegetative cells - metabolically active endospore cells
32
Name and describe 3 possible locations for endospores in the cell.
## Footnote
3-10 Endospore Stain
- Middle (central)
- Terminal (ends)
- Subterminal (between middle and end)
33
How old do the cultures of endospore-forming bacteria need to be before the bacteria start producing endospores?
## Footnote
3-10 Endospore Stain
Approximately 5 days
34
Endospores can be differentiated based on shape: they can be _______________ or ________________.
## Footnote
3-10 Endospore Stain
Spherical or elliptical (oval)
35
The 2 best-known genera of endospore-producing bacteria are:
## Footnote
3-10 Endospore Stain
Bacillus and Clostridium
36
List 4 diseased caused by endospore-forming bacteria and the genus and species of the pathogen that causes each disease.
## Footnote
3-10 Endospore Stain
*B.anthracis* - anthrax
*B.cereus* - food poisoning
*C.tetani* - tetanus
*C.botulinum* - botulism
*C.perfringens* - gas gangrene
37
If a basic stain like crystal violet is applied to a bacterial smear that contains endospores (without using steam), what will the endospores look like and why?
## Footnote
3-10 Endospore Stain
They would remain transparent as the thick protein (keratin) coat prevents staining
38
What will the vegetative cells look like after being stained with crystal violet and why?
## Footnote
3-10 Endospore Stain
- Purple
- The protein coat would not be formed around a vegatative cell and therefore would stain
39
The process by which endospores return to the vegetative state is called _______________________.
## Footnote
3-10 Endospore Stain
germination
40
Under what conditions do bacteria produce endospores? What is the advantage of the endospores to the bacteria?
## Footnote
3-10 Endospore Stain
- Temperature, UV light, O2, pH, H2O, food stress
41
How long can endospores remain viable (capable of germinating into vegetative cells)?
## Footnote
3-10 Endospore Stain
Millions of years
42
Acid-fast bacterial cell walls are produced by the genus __________________________. Two diseases caused by this genus include ________________________ and __________________________.
## Footnote
3-8: Acid-Fast Stain
- Mycobacterium
- Lung tuberculosis
- Leprosy
43
Acid-fast cell walls are primarily made of ____________________ _________. Consequently, these cells are sticky and waxy.
## Footnote
3-8: Acid-Fast Stain
- 60% mycolic acid
44
Describe how acid-fast bacteria can to survive for longer in their environment. Give at least 3 ways.
## Footnote
3-8: Acid-Fast Stain
- Adherence factor
- Protection against phagocytic digestion
- Protects against dehydration
- Chemical protection (antibiotics and disinfectants)
45
Describe why carbolfuchsin dye must be heated and steamed during the acid-fast staining procedure.
## Footnote
3-8: Acid-Fast Stain
- Carbolfuchsin is lipid soluble and penetrates the waxy cell wall when steamed as outer surface is softened
46
After the acid-fast staining procedure, acid-fast cells will have the color ____________________ while non-acid-fast cells will have the color _____________________.
## Footnote
3-8: Acid-Fast Stain
- Pink
- Blue
47
During the last step of the acid-fast staining procedure, methylene blue is applied for 1 minute and then rinsed off. Explain why only some cells absorb the blue dye.
## Footnote
3-8: Acid-Fast Stain
- Acid-Fast positive cells have mycolic acid layer that can resist methylene blue staining.
48
When working with acid-fast bacteria, an inoculating ________________ (rather than a needle) should be used to obtain and mix the bacteria into an emulsion during the smear preparation. Why is this important?
## Footnote
3-8: Acid-Fast Stain
- Loop
- Becuase mycobacterium is sticky and would be hard to get on the stain with a needle
49
The non-pathogenic acid-fast genus and species of bacterium used in this experiment is called __________________ ____________________ and may cause an odor on the skin referred to as _________________ when it overgrows or is not washed by regular bathing.
## Footnote
3-8: Acid-Fast Stain
- Mycobacterium smegmatis
- Smegma
50
_________________________ _________________________. Although it does not cause disease, it does cause a condition called _____________________ when it overgrows on human skin.
- Mycobacterium smegmatis
- Panniculitis
51
Capsules may be produced by certain bacteria and contribute to an increased ability to _______________ and adhere to surfaces.
## Footnote
3-9: Capsule Stain
Survive
(capsules can help bacteria stay hydrated)
52
Capsules are made of mucoid ____________________________ or ____________________________ that are secreted onto the ___________________ of bacterial cells.
## Footnote
3-9: Capsule Stain
- Polysaccharides
- Polypeptides
- Outer surface
53
Describe how capsules allow bacteria to survive for longer in their environment. Give at least 3 ways.
## Footnote
3-9: Capsule Stain
- Adherance factor (sticky)
- Antibiotic, antiseptic, disinfectant resistant
- Capsules allow for protection from dehydration and food source
- Anti-phagocytic properties
54
During the capsule staining procedure, congo red acts to stain the ______________________, while safranin stains the _______________________, leaving the capsule ________________________.
## Footnote
3-9: Capsule Stain
- Background
- Bacterial cell
- Transparent
55
The capsule stain employs both simple and negative staining procedures. Yet, the capsule does not absorb any dye, why might this be?
## Footnote
3-9: Capsule Stain
The capsule has a neutral charge
56
Why is hydrochloric acid applied during the capsule staining procedure? (2 reasons)
## Footnote
3-9: Capsule Stain
- Kills Bacteria
- Coagulates proteins
57
When working with potential pathogens, a capsule stain should be prepared with a beveled edge slide (with cut corners) to make the initial smear. How does the beveled edge help with safety?
## Footnote
3-9: Capsule Stain
It prevents bacterial sample from dripping over the edge of the slide
58
Some species of capsule-producing bacteria are environmental and non-pathogenic. However, there are some well-known diseases caused by bacteria that produce capsules. Name two diseases in this category and their causative agents.
## Footnote
3-9: Capsule Stain
Bacillus anthracis - Anthrax
Streptococcus pneumoniae - Pnuemonia
59
Fermenters in this test ___________________ the medium more that do oxidizers. (____________ the pH)
## Footnote
6-2: Oxidation-Fermentation (O-F) test
- Acidify
- Lowering
60
Why does this medium have a high sugar-to-peptone ratio?
## Footnote
6-2: Oxidation-Fermentation (O-F) test
To reduce the possibility that alkaline products from peptone utilization will neutralize weak acids made from carb metabolization
61
The pH indicator in this medium is bromothymol blue, which is _____________ at pH 6.0 and ______________ at pH 7.1.
## Footnote
6-2: Oxidation-Fermentation (O-F) test
-Yellow
-Green
62
The lower-than-usual concentration of agar in this medium allows the student to determine ____________________ of the organism as well as its oxidative or fermentative abilities.
## Footnote
6-2: Oxidation-Fermentation (O-F) test
Motility
63
The fermentable carbohydrate that we have included in this medium is _______________________.
## Footnote
6-2: Oxidation-Fermentation (O-F) test
Glucose
64
After inoculation, one tube of O-F medium for each organism is sealed with a layer of mineral oil to promote ____________________________ and __________________________; the other tube for this organism does not get a layer of mineral oil, in order to promote ___________________________ and _______________________.
## Footnote
6-2: Oxidation-Fermentation (O-F) test
- Anaerobic growth
- Fermentation
- Aerobic growth
- Oxidation
65
If an organism grows in this medium, either with or without the mineral oil, and turns the medium blue, why did this change occur? What did the organism use as a food source? Is the appearance of a blue color in the medium a positive or negative test for the oxidation or fermentation of carbohydrate and why?
## Footnote
6-2: Oxidation-Fermentation (O-F) test
- The blue indicated a raised (alkaline) pH
- Peptones were used **not glucose**
- Negative test for both because oxidation of peptones occured not the breakdown of **carbohydrates**
66
What do you call an organism (oxygen requirements) that can ferment and oxidize the carbohydrate in this experiment (and which bacteria that we looked at fell in this category)? What do you call an organism that can oxidize the carbohydrate but not ferment it (and which bacteria that we looked at fell in this category)?
## Footnote
6-2: Oxidation-Fermentation (O-F) test
- Facultative anaerobe
- Escherichia coli
- Obligate aerobe
- Psuedomonas aeruginosa
67
Our OF medium contains glucose, but it could contain the carbohydrate __________________ or the carbohydrate ________________________.
## Footnote
6-2: Oxidation-Fermentation (O-F) test
- Lactose
- Sucrose
68
A “lactose fermenter” is an organism that splits the ____________________ lactose into _________________ and ______________________, and then ferments the ___________________________.
## Footnote
5-3: Phenol Red Broth
- Disaccharide
- Glucose
- Galactose
- Monosaccharides
69
The Methyl-Red (MR) test detects bacteria capable of performing a ______________________ fermentation.
## Footnote
5-3: Phenol Red Broth
Mixed acid
70
The Voges-Proskauer (VP) test identifies bacteria able to produce ________________________ as part of a ___________________________ fermentation.
## Footnote
5-3: Phenol Red Broth
- Acetoin
- 2,3-butanediol
71
Phenol red broth contains a fermentable ________________, ________________, and the pH indicator __________________________.
## Footnote
5-3: Phenol Red Broth
- Carbohydrate
- Peptone
- Phenol Red
72
Phenol red is ____________________ below pH 6.8 and _____________________ above pH 7.4.
## Footnote
5-3: Phenol Red Broth
- Yellow
- Pink/Magenta
73
____________________ of amino acids in the peptone in this broth produces ____________________, which __________________ the pH and turns the broth _________________ or _______________ (colors); the color of the broth may also remain the same. Do these results indicate a positive or negative test for the fermentation of the carbohydrate and why?
| 5-3: Phenol Red Broth
- Deamination
- Ammonia
- Increases
- Yellow or Pink
- Yellow is a positive test of fermentation as it indicates carb metabolism resulting in mixed acids being produced
- Pink is a negative test of fermentation as it indicates peptone metabolism resulting in NH3 production
74
An inverted Durham tube (small test tube) is placed inside the culture tube to:
## Footnote
5-3: Phenol Red Broth
- Indicate gas production from fermentation
75
If the medium is examined after 18-24 hours of incubation, what does a yellow color indicate? Is this a positive or negative test for fermentation of the carbohydrate and why?
## Footnote
5-3: Phenol Red Broth
- Positive for carb fermentation
- Positive because phenol red indicator turns yellow in acid which is a byproduct of carb fermentation
76
To state that a particular organism is not capable of fermenting a particular carbohydrate (negative test), in addition to a color change, the medium must be _________________. If this last criterion is not met, why is it impossible to determine if that organism could ferment that carbohydrate?
## Footnote
5-3: Phenol Red Broth
- Cloudy
- There are two food sources. If it is not cloudy then neither food source was used
77
Why is it important to read these tubes after 24-48 hours after incubation? What color would the tube be after 48 hours? Why?
## Footnote
5-3: Phenol Red Broth
Before the 24 hrs. the microorganisms could breakdown the protein and turn the broth yellow for a short time until more alkaline products are made.
78
Glucose is included in MR-VP medium as a __________________________; the purpose of the phosphate buffer is:
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Substrate (fermentable carb)
- Resist pH change
79
The MR test is designed to detect organisms capable of _______________________ the buffer and ________________________________________.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Overcoming
- Lowering the pH
80
Bacteria that are MR+ carry out what is called a ______________________________________. The acids produced by these organisms tend to be ________________, whereas acids produced by other organisms tend to be:
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Mixed acid fermentation
- Stable
- Unstable and become neutral or alkaline
81
The pH indicator methyl red is _______________ at pH 4.4 and _______________ at pH 6.2 (note that this is exactly the opposite of the color range of the pH indicator __________________). Between pH 4.4 & pH 6.2, methyl red is various shades of _____________________.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Red
- Yellow
- Phenol red
- Orange
82
____________ color is considered the only true indication of a + result in the MR test; orange broth is considered _________________ or_________________. _______________________ is negative.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Red
- Negative
- Inconclusive
- Yellow
83
The VP test is designed to identify organisms that ferment glucose but quickly convert their acid products to ___________________ and ___________________________.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Acetoin
- 2,3-butanediol
84
A positive VP test is ________________ (color); no color change is _______________________.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Red
- Negative
85
A copper color in the VP test is the result of interaction between the reagents and should not be confused with the true __________________ color of a + result.
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Red
86
If an organism that cannot ferment glucose, grows in this broth, what did it use for a food source?
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Peptone
87
Why are organisms that are MR+ usually VP-, and VP+ organisms usually MR-?
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Because the organisms fermenting glucose either yields stable acids or acetoin which is more alkaline. Rarely does an organism produce both.
88
The MR and VP tests are components of a battery of tests known by the initials ____________________. Indicate what each of these letters stands for:
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- IMViC
89
All fermentation pathways start with the compound ____________________, produced by _______________________. (process)
## Footnote
5-4: Methyl Red & Voges-Proskauer Test
- Pyruvate
- Glycolysis
90
The only carbon-containing compound in citrate medium is ______________________. Why do organisms need a carbon source?
## Footnote
5-8: Citrate Test
- Citrate
- To make all macro molecules
91
The only nitrogen source in citrate medium is ________________________. Why do organisms need a nitrogen source (to make which 2 macromolecules)?
## Footnote
5-8: Citrate Test
- Ammonium dihydrogen phosphate
- Amino acids and nucleotides (DNA, RNA)
92
In a medium where citrate is the only available carbon source, bacteria that possess the enzyme ________________________________ can transport the citrate molecules into the cell and metabolize them.
## Footnote
5-8: Citrate Test
- Citrate Permease
93
The pH indicator in citrate medium, bromothymol blue, is _________________ at pH 6.9 and ________________ at pH 7.6.
## Footnote
5-8: Citrate Test
- Green
- Blue
94
Bacteria that survive in this medium and utilize the citrate create an _____________________ (increase or decrease?) in the pH of the medium.
## Footnote
5-8: Citrate Test
- Increase
95
Describe a positive result in this medium. Why does the pH indicator in the medium change color in a positive test? Indicate the name of the product and the relative pH (acidic or basic) that caused the color change.
## Footnote
5-8: Citrate Test
- Positive test shows utilization of citrate through breakdown of Ammonium dihydrogen phosphate which causes increase in pH leading to **blue color change**
96
Describe a negative result in this medium. Why is there no growth in a negative result?
## Footnote
5-8: Citrate Test
- Negative is green **with no growth**. if it is green with growth it is still positive as there likely has not been enough alkaline products produced yet
- There will be no growth as citrate could not be utilized and no alkaline products were produced
97
If there is growth on citrate medium after incubation but no color change, this is considered a ________________________ result.
## Footnote
5-8: Citrate Test
Positive
98
Citrate utilization is one part of a test series referred to as IMViC; these letters stand for the 4 tests:
## Footnote
5-8: Citrate Test
I: Indole
M: Methyl Red
Vi: Voges-Prskauer
C: Citrate
99
The presence of ammonium hydroxide in the medium is INDIRECT evidence that the bacterium has broken down __________.
## Footnote
5-8: Citrate Test
- Citrate
- Nitrogen is necessary for growth as is carbon so if basic products are produced it indicates the use of citrate as well.
100
What is the purpose of the decarboxylase test?
## Footnote
5-11: Decarboxylase
To determine whether or not bacteria can decarboxylate lysine or ornithine
101
What is the purpose of the deaminase test?
## Footnote
5-12: Deaminase
To determine whether bacteria can deaminate phenylalanine
102
What is the name of the medium?
## Footnote
5-11: Decarboxylase
Lysine/ornothine broth
- LDC or ODC
103
What is the substrate, bacterial enzyme, and end product?
## Footnote
5-11: Decarboxylase
Substrate: Lysine or Ornothine
Bacterial Enzyme: Lysine or Ornothine Decarboxylase (endoenzyme)
End Products: Cataverine or putrescine (alkaline diamines) + CO2 g
104
What is the appearance of a positive/negative?
## Footnote
5-11: Decarboxylase
Positive: Purple/gray
Negative: Yellow
105
What is the reagent and pH indicator?
## Footnote
5-11: Decarboxylase
- None
- Bromocresol purple
106
What else is important about this test? (4)
## Footnote
5-11: Decarboxylase
- Results cannot be read before 48H
- Anaerobic enzymes
- Decarboxylation is anaerobic (oil used)
- Glucose is used first then acids which activate decarboxylase enzymes
107
What is the name of the medium?
## Footnote
5-12: Deaminase
Phenylalanine agar
108
What is the substrate, bacterial enzyme, and end product?
## Footnote
5-12: Deaminase
Substrate: Phenylalanine
Bacterial enzyme: Phenolalanine deaminase (endoenzyme)
End product: Ammonia + phenylpyruvic acid
109
What is the appearance of a positive/negative?
## Footnote
5-12: Deaminase
Positive: Green
Negative: Yellow
110
What is the reagent and pH indicator?
## Footnote
5-12: Deaminase
Reagent: Ferric Chloride (FeCl3) (indicates phenols)
pH indicator: None
111
What else is important about this test?(2)
## Footnote
5-12: Deaminase
- pH products neutralize eachother
- Aerobic enzyme
112
Is protein deamination and decarboxylation an anaerobic or aerobic process?
Deamination - aerobic
Decarboxylation - anaerobic
113
Enzymes called decarboxylases catalyze the removal of the _________________ from an amino acid.
## Footnote
5-11: Decarboxylase Test
Carboxyl group
114
Enzymes called deaminases catalyze the removal of the ________________ from an amino acid.
## Footnote
5-11: Decarboxylase Test
Amines
115
What is meant by the substrate of an enzyme?
## Footnote
5-11: Decarboxylase Test
The amino acid that has its variable group removed (amine or carboxyl)
116
Decarboxylases catalyze reactions that produce ________________ (pH) products.
## Footnote
5-11: Decarboxylase Test
Alkaline
117
The pH indicator bromocresol purple is ______________ at pH 6.8 and above and ______________ below pH 5.2.
## Footnote
5-11: Decarboxylase Test
Purple
Yellow
118
Why is mineral oil added to the decarboxylase broth tubes before incubation?
## Footnote
5-11: Decarboxylase Test
To seal off from oxygen and encourage fermentation
119
Why does the decarboxylase-positive tube have to turn yellow before it can turn purple?
## Footnote
5-11: Decarboxylase Test
- Accumulation of acidic end products will occur first
- Then low pH organisms will react to acidic enviornment and either produce decarboxylases or not resulting in positive (purple) or negative (yellow) results
120
Describe a positive result in this experiment and describe a negative result. What kind of pH is present in a + result and is present in a - result?
## Footnote
5-11: Decarboxylase Test
Positive: Purple, Alkaline, decarboxylases resulted in an increase in pH
Negative: Yellow, Acidic, lack of decarboxylases meant pH remained negative
121
Why is glucose included in the decarboxylase broth?* (Hint: answer is not “as a food source”)
## Footnote
5-11: Decarboxylase Test
- Low glucose concentration promotes fermentation lowering pH and causing proteases to activate (decarboxylase)
122
This decarboxylation test cannot be performed successfully on organisms that cannot ferment glucose. Explain why this is the case.*
## Footnote
5-11: Decarboxylase Test
- If the organism cannot lower the pH through fermentation the proteases will not be activated and **no color change will occur**
123
Cadaverine and putrescine are examples of compounds known as __________________.
## Footnote
5-11: Decarboxylase Test
Diamines
124
The names, cadaverine and putrescine, suggest that the compounds might be found in _______________, which they are, as a result of the decarboxylation of ________________ (what molecule) by bacteria.
## Footnote
5-11: Decarboxylase Test
- Rotting Flesh
- Lysine -> Cadaverine
- Ornothine -> Putrescine
125
What is phenylalanine (what type of monomer is it)?
## Footnote
5-12: Phenylalanine Deaminase
- Amino Acid substrate
126
Phenylalanine is part of an ingredient found in the popular artificial sweeteners known as _________________ or ___________________.
## Footnote
5-12: Phenylalanine Deaminase
Aspartane
Nutrasweet
127
The enzyme that some bacteria can produce that removes an amino group from phenylalanine is called ___________________________________.
## Footnote
5-12: Phenylalanine Deaminase
Phenylalanine Deaminase
128
The reagent that is added to bacterial growth on phenylalanine deaminase agar in order to determine if the enzyme has been produced, is __________________________.
## Footnote
5-12: Phenylalanine Deaminase
Ferric Chloride
129
Describe a positive result in the experiment and a negative result.
## Footnote
5-12: Phenylalanine Deaminase
- Green indicates positive as Phenolpyruvate is present
- Yellow indicates negative as no phenolpyruvate is present
- Note this is not a pH test as the phenyl pyruvate and ammonium cancel eachother's pH
130
Phenylalanine is broken down to _____________________ and _____________________.
## Footnote
5-12: Phenylalanine Deaminase
Ammonium
Phenylpyruvic Acid
131
Why can’t you use a pH indicator to detect phenylalanine deamination?
## Footnote
5-12: Phenylalanine Deaminase
Because the Phenylpyruvic acid (acid) and Ammonium (base) cancel eachother's pH
132
A green color results in this experiment if _______________________________ reacts with the reagent ________________________.*
## Footnote
5-12: Phenylalanine Deaminase
Phenylpyruvic Acid
Ferric Chloride
133
Like all amino acids, phenylalanine is a source of the two elements ______________ and _____________ for the bacteria.
## Footnote
5-12: Phenylalanine Deaminase
Nitrogen
Carbon
134
Write the chemical formula for an amine group (amino group).
## Footnote
5-12: Phenylalanine Deaminase
NH2
135
What is the difference between the deamination and the decarboxylation of an amino acid (Hint: think of oxygen requirements)?
## Footnote
5-12: Phenylalanine Deaminase
Decarboxylation occurs in anaerobic conditions
Deamination occurs in aerobic conditions
136
What is the purpose of the Kirby-Bauer Test?
## Footnote
7-3: Kirby-Bauer Test
To perform a culture and antibiotic sensitivity test on an organism
137
What was the medium of this test? (5)
## Footnote
7-3: Kirby-Bauer Test
Mueller-Hinton Agar standardizes the following
- pH:7.4
- Soft agar
- 4mm depth agar for lateral diffusion
- Temp: 37 C
- Amount of drug
138
What were the three levels of susceptibility?
## Footnote
7-3: Kirby-Bauer Test
Sensitive: A normal dose is effective against bacteria
Intermediate: A higher than normal dose of an antibiotic is required
Resistant: No acceptable dose is effective
139
What is synergy, broad spectrum, narrow spectrum?
## Footnote
7-3: Kirby-Bauer Test
Synergy: when the effect of two drugs combines to be greater than their sum
Broad spectrum: Drugs that are effective against most bacteria typically reserved as final options as it can harm native flora
Narrow spectrum: Highly targetted drugs that are effective against a specific mecanism of bacterial growth. Must know what bacteria you are dealing with
140
The quantitative sensitivity disk method of antibiotic sensitivity testing is called the _________________
method.
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
Kirby-Bauer
141
In this method, the diameter of the ___________________________ around the disk is measured to the
nearest _____________________ (unit).
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
Zone of inhibition
Milimeters
142
The inhibition zone diameter that is produced in this experiment will indicate the ___________________ of a bacterium to each antibiotic.
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
Sensitivity
143
How do you determine if an organism is susceptible to a particular antibiotic in this test? How do you determine if the organism is resistant?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
The susceptibility zone is measured and compared to a document that states according to what antibiotic is being used a diameter under X is resistant and over X is susceptible
144
What will a negative test for antibiotic sensitivity look like? Describe such a result and explain what it means.
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
A negative would be shown as no ZOI or a small ZOI. This means that the antibiotic was unable to stop or kill the bacteria
145
What will a positive test for antibiotic sensitivity look like? Describe such a result and explain what it means.
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
A large ZOI that is greater than the susceptibility break point
ex. Breakpoint <10mm, actual D = 18mm
146
Why is it important that the sensitivity disks used in this experiment contain a specific, standardized amount of antibiotic?* How is this test standardized (i.e. what is standardized in this test)?(4)
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
- To ensure all results are reliable and safe for humans
- The agar is 4mm (thinner than usual) to promote lateral diffusion
- pH is kept to 7.2-7.4 to mimic blood pH
- Agar is incubated at 37 degrees C to mimic human body temp
- Agar is incubated for 18 hours to select for younger bacteria
147
Why is it important that the results of antibiotic sensitivity test guide treatment of bacterial infections?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
It allows us to understand how different drugs interact with bacteria and what is an effective medication that could be used to adress a bacterial infection appropriately
148
Penicillin is an antibiotic produced by the mold ________________________ (genus), which is also responsible
for __________________________ (type of food).
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
Penicillium
Cheese
149
What is “intermediate susceptibility” to an antibiotic?* Under what conditions would it be appropriate to use an antibiotic to which a particular organism was intermediately susceptible?*
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
- When the ZOI is above resistant but below susceptibility
ex. R<5, I=6-8, S>9
- Appropriate if the person is allergic to other antibiotics or can be used with another drug for enhanced effects
150
True or false: All bacteria found within the clear area around the disks are dead. Why did you answer true or false?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
False. There are bacteriostatic antibiotics which are not bacteriocidal. Often times with gram negative infections when they are lysed they release lipid-A which is toxic and can cause shock and even death. Therefore a bacteriostatic drug is better to pause development and allow the patient's body to fight the infection in a safer way
151
What is a broad-spectrum antibiotic? When would it be better to use a broad-spectrum antibiotic? Why?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
A broad-spectrum antibiotic is an antibiotic that many bacteria are susceptible both gram positive and gram negative. Broad spectrum antibiotics are generally reserved as a last ditch effort as it also kills natural flora. Otherwise targetted antibiotics are usually more appropriate
152
What is a narrow spectrum antibiotic? When would it be better to use a narrow spectrum antibiotic? Why?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
Narrow spectrum antibiotics are antibiotics that are effective at targetting a specific bacteria. This is effective when you know exactly what the bacterial infection is and will not affect your natural flora
153
What is drug synergy? What does plate look like if two drugs are synergistic?
## Footnote
7-3 Antibiotic Sensitivity Testing (Kirby-Bauer Method)
- Drug synergy is when antibiotics combine and have a greater effect together than their individual effects summed
- If the drugs synergize the 'halo' between the two drugs will be bigger than the halo around the drug itself
