Lab 2 Flashcards
Catalase:
What is the chemical equation for the reaction that’s occurring?
2H2O2 -> 2H2O + O2
In exercise 5.6, what enzyme is being evaluated?
Catalase
Catalase:
What types of bacteria will have catalase?
- Obligate aerobe
- Facultative anaerobe
- Microaerophile
What observation indicates a positive catalase test? Negative catalase test?
Positive catalase = bubbles
Negative catalase = no bubbles
Mannitol Salt Agar is what type of media?
Selective and Differential
What is the purpose of the salt in Mannitol Salt Agar?
It selects for growth in the presence of salt
What is the purpose of the mannitol in Mannitol Salt Agar?
It differentiates for fermentation of mannitol
What is the pH indicator used in Mannitol Salt Agar?
Phenol red
Mannitol Salt Agar:
What observation indicates a positive fermentation result? Negative fermentation result?
+ fermentation = yellow growth/halo (media)
negative fermentation = red growth/no halo (media)
What type of media is the nutrient agar in Mannitol Salt Agar?
What is the purpose of the nutrient agar plate using the same bacteria?
- Complex
- Control
Give an example of a bacteria that will grow on MSA. Name one that won’t.
One that will: Staphylococcus aureus
One that won’t: E. coli
What specific bacteria is this media (Mannitol Salt Agar) primarily used to detect?
Staphylococcus aureus
MacConkey Agar
Which type of media is this?
Selective and Differential
MacConkey Agar
What carbohydrate is present in this media?
Lactose
MacConkey Agar
What is the purpose of crystal violet?
Inhibits G+
MacConkey Agar
What is the pH indicator?
Neutral red
MacConkey Agar
What observation indicates a positive (lactose) fermentation result? Negative?
+ = pink colonies, lactose fermentation
- = cream colonies, no lactose fermentation
MacConkey Agar
What type of media is the nutrient agar?
What is the purpose of a nutrient agar plate with the same bacteria?
- Complex
- Control
Eosin Methylene Blue Agar
What type of media is this?
Selective and Differential
Eosin Methylene Blue Agar
What carbohydrate is present in this media?
Lactose
Eosin Methylene Blue Agar
What is the purpose of eosin Y and methylene blue dyes?
Inhibits G+ AND reacts with lactose fermenters (indicator)
Eosin Methylene Blue Agar
What observation indicates a positive fermentation result? Negative fermentation result?
+ = pink –> metallic green colonies (is a fecal coliform)
negative = cream, (not a fecal coliform)
Eosin Methylene Blue Agar
What specific group of bacteria should grow well on this media?
Fecal coliform
Eosin Methylene Blue Agar
What type of media is the nutrient agar?
What is the purpose of a nutrient agar plate with the same bacteria?
- Complex
- Control
Bile Esculin Agar
Which type of media is this?
Selective and Differential
Bile Esculin Agar
What is the purpose of the bile?
Added to separate Group D strep from Non-Group D strep
Bile Esculin Agar
What is the purpose of ferric citrate?
Reagent indicating a positive result
Bile Esculin Agar
What enzyme is being evaluated?
Esculinase
Bile Esculin Agar
What observation indicates a positive test? Negative test?
+ = black, has esculin, works in presence of bile
negative = tan, no esculin, no bile
Bile Esculin Agar
What specific group of bacteria should grow well on this media?
Group D Strep and Enterococci
Blood Agar
Which type of media is this?
Enriched and Differential
Blood Agar
What is the name of the exotoxin being evaluated?
Hemolysin
Blood Agar
What is the purpose of the streak-stab technique?
Streak = to isolate colonies
Stab = anaerobic environment
Blood Agar
What is the difference between beta, alpha, and gamma hemolysis? Be able to recognize the difference between the various forms of hemolysis.
Alpha = partial breakdown
Gamma = no breakdown
Beta = complete breakdown
Blood Agar
What is meant by fastidious?
Hard to grow
Bacitracin/Novobiocin
Define the “zone of inhibition”
Diameter of space where growth is inhibited
Bacitracin/Novobiocin
What is the mechanism of action for Bacitracin? Novobiocin?
Bacitracin = inhibits cell wall
Novobiocin = inhibits DNA gyrase
Bacitracin/Novobiocin
What is the necessary zone of inhibition for bacitracin to be considered susceptible/resistant?
Susceptible = > 10 mm (greater than 10 mm)
Resistant = < 10 mm (less than 10 mm)
Bacitracin/Novobiocin
What is the necessary zone of inhibition for novobiocin to be considered susceptible/resistant?
S = >16 mm
R = < 16 mm
Kirby Bauer
What is the specific name of the agar used in this test?
Muller Hinton Agar
Kirby Bauer
Define the “minimum inhibitory concentration”. Where is this located on the plate?
The junction where the concentration of the antibiotic became too low to inhibit the growth
Kirby Bauer
What is meant by Susceptible? Intermediate? Resistant?
S = antibiotic works
I = antibiotic may work
R = antibiotic does not work
Phenol Red Broth
Which type of media is this?
Differential
Phenol Red Broth
What is the pH indicator used in this test?
Phenol red
Phenol Red Broth
What observation indicates a positive fermentation result? Negative result?
+ fermentation = yellow, aka A/G or A/-
- fermentation = red
Phenol Red Broth
What observation indicates a positive deamination result? Negative result?
+ deamination = pink
- deamination = red
Phenol Red Broth
What is the purpose of the Durham tube?
Captures CO2
Phenol Red Broth
Know the symbols (A, G, K, -) and be able to use these to describe a phenol red tube.
A= yellow
G= bubble
K= pink
- = red or no airbubble
A/-
yellow, no airbubble
A/G
yellow, air bubble
-/-
red, no airbubble
K
pink
Methyl Red and Voges Proskauer Tests
Which type of media is this?
Differential
Methyl Red and Voges Proskauer Tests
What does the Methyl Red test determine?
Mixed acid fermentation
Methyl Red and Voges Proskauer Tests
What does the Voges Proskauer test determine?
Acetoin production
Methyl Red and Voges Proskauer Tests
What observation indicates a positive Methyl Red test? Negative result?
+ = cherry red
- = yellow/orange
Methyl Red and Voges Proskauer Tests
What observation indicates a positive Voges Proskauer test? Negative result?
+ = wine red
- = copper
Methyl Red and Voges Proskauer Tests
What reagents are added to test for MR?
Methyl red indicator
Methyl Red and Voges Proskauer Tests
What reagents are added to test for VP?
Naphthol and Potassium hydroxide
Decarboxylation Tests
What type of media is this?
Differential
Decarboxylation Tests
What is the specific name of the media used?
Moller’s Decarboxylase Broth
Decarboxylation Tests
What is the pH indicator used in this test?
Bromocresol purple
Decarboxylation Tests
What is the incubation period?
96 hours
Decarboxylation Tests
What three amino acids are being tested?
Lysine, Arginine, Ornithine
Decarboxylation Tests
What observation indicates no fermentation and no decarboxylation?
tan
Decarboxylation Tests
What observation indicates fermentation but no decarboxylation?
yellow
Decarboxylation Tests
What observation indicates decarboxylation?
purple
Decarboxylation Tests
What is the end product of decarboxylation?
CO2
Decarboxylation Tests
What’s the purpose of mineral oil
Promotes fermentation
Deamination Test
What type of media is this?
Differential
Deamination Test
What enzyme is present in bacteria that are positive?
Phenylalanine deaminase
Deamination Test
What is the end product of deamination?
NH3
Deamination Test
What reagent is used in this test?
Ferric chloride
Deamination Test
What observation indicates a positive test? A negative test?
+ = green
- = yellow
SIM
What type of media is this?
Differential
SIM
What 3 things are assessed in a single SIM test?
Sulfur reduction, Indole production, and Motility
SIM
What is the purpose of Fe in this media?
Reagent indicating a positive result for Sulfer reduction
SIM
What enzyme is present in a bacteria if it reduces sulfur?
Cysteine desulfurase
SIM
What enzyme is present in a bacteria if it is indole positive?
Tryptophanase
SIM
What reagent is used to determine if indole positive?
Kovac’s reagent
SIM
What observation indicates a positive sulfur reduction result? Negative result?
+ = black
- = tan
SIM
What observation indicates a positive indole result? Negative result?
+ = red layer on top
- = yellow layer on top
SIM
What observation indicates a positive motility result? Negative result?
+ = growth radiates from stab line
- = defined stab line
SIM
How else can motility be assessed?
Wet mount
Citrate Utilization Test
What type of media is this?
Differential
Citrate Utilization Test
What enzyme must the bacteria have if it is citrate positive?
Citrate permease
Citrate Utilization Test
What provides a carbon source in this media? Nitrogen source?
Carbon = Citrate
Nitrogen = Ammonium
Citrate Utilization Test
What is the pH indicator?
Bromothymol blue
Citrate Utilization Test
What is the purpose in using an inoculating needle instead of a loop?
To avoid heavy inoculum which would cause a false positive
Citrate Utilization Test
What observation indicates a positive test result? Negative test result?
+ for citrate = blue or green with growth
- for citrate = green with no growth
Beta looks like
a fried egg with halo around
Alpha looks
green gray with a very slight halo
Gamma has
no halo, just a colony