Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
78 Cards in this Set
- Front
- Back
|
T/F Salmonella and Shigella are considered to be normal flora of the intestinal tract
|
False: Salmonella and Shigella are NOT considered to be normal flora of the intestinal tract and are pathogens causing food poisoning, diarrhea and bacterial dysentery
|
|
|
T/F Most of the Enerobacteriaceae are morphologically similar
|
True
|
|
|
Enterics are faculatively anerobic, either _______ or ________.
|
respiring or fermenting
|
|
|
Where do enterics mainly thrive?
|
Enterics inhabit vast types of environments, from soil, animals, fruits, and vegetables to humans
|
|
|
Do all enteric posses the enzyme to break down lactose? glucose?
|
All enterics are able to ferment glucose, but not all possess the enzymes required to breakdown lactose.
|
|
|
T/F Salmonella and Shigella are considered to be normal flora of the intestinal tract
|
False: Salmonella and Shigella are NOT considered to be normal flora of the intestinal tract and are pathogens causing food poisoning, diarrhea and bacterial dysentery
|
|
|
T/F Most of the Enerobacteriaceae are morphologically similar
|
True
|
|
|
Enterics are faculatively anerobic, either _______ or ________.
|
respiring or fermenting
|
|
|
Where do enterics mainly thrive?
|
Enterics inhabit vast types of environments, from soil, animals, fruits, and vegetables to humans
|
|
|
Do all enteric posses the enzyme to break down lactose? glucose?
|
All enterics are able to ferment glucose, but not all possess the enzymes required to breakdown lactose.
|
|
|
Which enzymes enable a bacterium to breakdown (ferment) lactose?
|
If a particular bacterium produces the enzymes beta-galactosidase and lactose permease, it is able to use lactose as a sole carbon source.
|
|
|
T/F Lactose is a disaccaride that can eventually be broken down into a SINGLE glucose molecule
|
False: Lactose is a disaccaride that can eventually be broken down into 2 glucose molecules
|
|
|
Will fermentation of lactose produce acidic or basic end products?
|
Acidic end products
|
|
|
What is the key determinative factor that indicates a positive result for lactose fermentation?
|
Acidity. Fermentation of lactose will produce acidic end products. This decreases the pH of the surrounding media, changing the color of the chosen pH indicator and essentially allowing lactose fermentation to be detected.
|
|
|
Define: Coliforms
|
Organisms that CAN ferment lactose
|
|
|
Define: Paracolons
|
Organisms that CANNOT ferment lactose
|
|
|
What kind of medium is the MacConkey agar?
|
Selective and Differential
|
|
|
What does the MacConkey agar contain?
|
The MacConkey agar contains bile salts and crystal violet
|
|
|
Why does the MacConkey agar select for gram-negative bacteria and inhibits the growth of gram-positive bacteria?
|
MacConkey agar contains crystal violet. Bacteria (gram-positive) have thick layers of peptidoglycan cell walls. Crystal violet becomes trapped within the cell wall complex, inhibiting the uptake of nutrients and ultimately colony growth.
|
|
|
Bile salts are _______
|
Detergents
|
|
|
Which enzymes enable a bacterium to breakdown (ferment) lactose?
|
If a particular bacterium produces the enzymes beta-galactosidase and lactose permease, it is able to use lactose as a sole carbon source.
|
|
|
T/F Lactose is a disaccaride that can eventually be broken down into a SINGLE glucose molecule
|
False: Lactose is a disaccaride that can eventually be broken down into 2 glucose molecules
|
|
|
Will fermentation of lactose produce acidic or basic end products?
|
Acidic end products
|
|
|
What is the key determinative factor that indicates a positive result for lactose fermentation?
|
Acidity. Fermentation of lactose will produce acidic end products. This decreases the pH of the surrounding media, changing the color of the chosen pH indicator and essentially allowing lactose fermentation to be detected.
|
|
|
Define: Coliforms
|
Organisms that CAN ferment lactose
|
|
|
Define: Paracolons
|
Organisms that CANNOT ferment lactose
|
|
|
What kind of medium is the MacConkey agar?
|
Selective and Differential
|
|
|
What does the MacConkey agar contain?
|
The MacConkey agar contains bile salts, crystal violet, lactose, and the pH indicator neutral red.
|
|
|
Why does the MacConkey agar select for gram-negative bacteria and inhibits the growth of gram-positive bacteria?
|
MacConkey agar contains crystal violet. Bacteria (gram-positive) have thick layers of peptidoglycan cell walls. Crystal violet becomes trapped within the cell wall complex, inhibiting the uptake of nutrients and ultimately colony growth.
|
|
|
Bile salts are _______
|
Detergents
|
|
|
What is the pH indicator used for MacConkey agars?
|
Neutral Red
|
|
|
What color is the pH indicator Neutral Red at a pH of 8? At a pH of 4?
|
Colorless at a pH of 8, Magenta/bright pink at a pH of 4.
|
|
|
MacConkey agar: What pH change can be expected when lactose is fermented? Will there be a color change? Coliforms or paracolons?
|
When lactose is fermented, the pH is lowered (more acidic) causing the coliforms to turn red.
|
|
|
Does the MacConkey agar differentiate between gram-negative bacteria or gram-positive bacteria?
|
Differentiate between gram-negative bacteria.
|
|
|
What type of medium is the Eosin Methylene Blue Levine agar (EMB)?
|
Selective and Differential
|
|
|
What does the EMB agar differentiate between?
|
This medium is used for differentiation of enteric lactose fermentors and non-lactose fermentors
|
|
|
What does the EMB agar contain?
|
Lactose, two dyes eosin as well as methylene blue
|
|
|
What do the dyes eosin and methylene blue partially inhibit? Gram-positive bacteria or gram-negative bacteria?
|
Gram-Positive bacterai
|
|
|
EMB agar: Lactose fermentors will undergo what color change? What is this color change dependent on?
|
Lactose fermentors will appear deep purple or blue/black with a metallic green sheen. The degree of acidity produced through fermentation will dictate the color change.
|
|
|
EMB agar: What is observed if a strong acid is produced through fermentation
|
Strong acid production causes the dyes to precipitate out onto the cell's surface, giving a metallic green appearance.
|
|
|
EMB agar: What is observed if bacteria does NOT ferment lactose?
|
Bacteria the do not ferment lactose will produce colorless colonies, but sometimes because of the color of the media, appear light pinkish/purple colors.
|
|
|
EMB agar: Bacteria appears pinkish/purple in coloration. Was the lactose fermented?
|
Bacteria did NOT ferment lactose
|
|
|
The acronym SS is the abbreviation for what agar?
EMB? |
Salmonella-Shigella, Eosin Methylene Blue Levine
|
|
|
Which agar is NOT both selective and differential mediums?
MacConkey/Blood agars |
Blood agar is differential but NOT selective
|
|
|
Define: Selective Media.
|
Used to select and isolate specific types of bacteria by containing chemical substances that allow the growth of a particular organism, while inhibiting the growth of other organisms.
|
|
|
Define: Differential Media
|
Contains chemical compounds that allow bacteria to be distinguished between each other based on their reactions to the compounds on the media
|
|
|
This media produces a characteristic change in the appearance of the bacteria growth and the media it is growing on
|
Differential
|
|
|
These are incorporated into the medium to allow change in pH to be observed as a color change to the medium
|
pH Indicator
|
|
|
This medium contains ingredients that inhibit/select for a certain type of bacteria AND has components that allow differentiation between bacteria that do grow
|
Selective/Differential Media
|
|
|
SS agar: Is used to identify and isolate salmonella/Shigella from what bacteria?
|
Enteric Bacterias
|
|
|
What does SS agar contain?
|
Bile salts, the dye brilliant green, lactose, the pH indicator Neutral Red, Sodium thiosulfate, a source of iron, and ferric citrate.
|
|
|
Which agars contain the pH indicator Neutral Red?
|
MacConkey and Salmonella/Shigella agars
|
|
|
SS agar: Which bacteria does the dye brilliant green serve to select against? Does it select any bacteria?
|
Brilliant green serves to select AGAINST gram positive bacteria and will select SOME gram-negative bacteria.
|
|
|
SS agar: Which type of organism will appear red. Coliforms/Paracolons? Why?
|
Coliforms that are able to grow will appear red from the neutral red, while paracolons will be colorless. The coliforms that appeared red are able to ferment the lactose contained within the media
|
|
|
SS agar: Bacteria streak appeared to have a black center. What can be concluded from this observation.
|
Bacteria that are able to produce H2S will appear to be an insoluble black precipitate
|
|
|
What substance present in the SS agar acts as a H2S indicator?
|
Ferric citrate
|
|
|
What can enteria bacteria produce from sodium thiosulfate?
|
Some enteric bacteria can produce colorless hydrogen sulfide gas from sodium thiosulfate.
|
|
|
Why is sodium thiosulfate included in the SS medium? How can this be beneficial when differentiating bacterium?
|
To act as a sulfur source in H2S gas production. Bacteria that are able to produce H2S will have a black center in the colonies or streak.
|
|
|
Which agars contain sodium thiosulfate and ferrous sulfate? What do these compounds test for?
|
SS and TSI agars, test for hydrogen sulfate (H2S) gas production.
|
|
|
Which agars utilize the pH indicator rphenol red?
|
Mannitol Salt Agar and Triple Sugar Iron Agar
|
|
|
Citrate is an intermediate in what cycle?
|
The TCA cycle
|
|
|
T/F The citrate medium can be used to select for and differentiate between organisms that are able to use citrate when no other fermentable carbohydrates are present?
|
True
|
|
|
If an organism is able to produce the enzyme citrase, will it grow on the TSI slate medium?
|
If the bacterium produces the enzyme citrase, it will use the citrate as its sole carbon source. TSI slates are used to differentiate between bacteria based on their ability to ferment glucose, lactose and/or sucrose.
|
|
|
Which sugar molecule would ferment first? Lactose? Sucrose?
|
Depends on which enzyme the bacteria is able to produce to catalyze the hydrolysis of the sugar present. Sucrase or Lactase
|
|
|
Citrate Agar: Which pH indicator is utilized.
|
Bromothymol Blue
|
|
|
Citrate Agars: What color change would be observed under a pH of 12? What does this color change indicate?
|
The medium will turn from green to deep blue. This color change indicates citrate is the sole carbon source.
|
|
|
MacConkey agar: Coloration of medium? Composed of? Which selects for? Changes if positive of lactose fermentation?
|
Muted Yellow. Crystal violet, bile salts, selects for gram - bacteria which inhibiting gram + bacteria, Positive for lactose production clear (yellowish) halo surrounding red
|
|
|
EMB agar: Coloration of medium? Composed of? Which selects for? Changes if positive for lactose fermentation?
|
Deep Red, Contains lactose and two dyes --> eosin and methylene blue, selects for gram - while inhibiting gram + bacteria, Positive for lactose production yield metallic green colorations
|
|
|
SS agar: Coloration of medium? Composed of? Which selects for? Changes if positive for lactose fermentation?
|
Yellowish, bile salts green dye brilliant green, selects for some gram - bacteria, selects against gram +, positive for fermentation red coloration also if positive for sulfide gas production --> black coloration
|
|
|
Which two agars contain pH indicator neutral red
|
MacConkey and SS
|
|
|
Which agar inhibits gram + bacteria
|
All three agars inhibit gram + bacteria
|
|
|
Escherichia Coli is an example of what bacteria type?
|
Gram Negative
|
|
|
Klebsiella pneumoniae
|
Gram Negative
|
|
|
Yersinia enterocolitica
|
Gram Negative
|
|
|
Salmonella enterica
|
Gram Negative
|
|
|
Negative Sal yer pneu coli
|
Salmonella enterica, Yersinia enterocolitica, Klebsiella pneumoniae, and Escherichia coli are all gram negative bacteria
|
|
|
Staph epi aureus
|
Staphylococcus epidermidis and aureus
|
|
|
epidermidis and aureus both from what genus
|
Staphylococcus
|
