Shared Flashcard Set

Details

Lab Content Quize
Virulence Factors, Kirby-Bauer Disk Test, Staph Aureus
56
Microbiology
Undergraduate 2
11/24/2014

Additional Microbiology Flashcards

 


 

Cards

Term
The Gelatin Hydrolysis Test tests for what?
Definition
Presence of gelatinases that hydrolyze proteins found found in host connective tissue. (Collagen and Gelatin)
Term
The Gelatin Hydrolysis Test that consists of a liquid after culture of a bacterium indicates what?
Definition
The presence of gelatinases in the bacterium.
Term
What growth media is used for the Gelatin Hydrolysis Test?
Definition
Nutrient Gelatin - beef extract, peptone and gelatin
Term
Cultures of S. Aureus and E. Aeroginosa are incubated in a Nutrient Gelatin media. What will be the consistency of the test tube?
Definition
Solid
Term
Of S. aureus, S. epidermidis, S. marcescans and E. aerogenosa, which media will be liquid after incubation in Nutrient Gelatin growth media?
Definition
S. aureus and S. marcescans
Term
What type of bacteria produce hemolysins?
Definition
Gram positive pathogenic bacteria
Term
What are hemolysins?
Definition
Exotoxins that damage RBCS
Term
What media is used for the hemolysis test?
Definition
Blood agar - Tryptic soy agar and 5% sheep blood
Term
What are three examples of hemolytic bacteria?
Definition
Staphylococcus, streptococcus and listeria
Term
The partial destruction of RBC's and a greenish discoloration in the media indicates the presence of what?
Definition
alpha-hemolysins
Term
The complete destruction of RBC's and a clearing in the media indicates the presence of what?
Definition
Beta-hemolysins
Term
What are DNases?
Definition
Produced by bacteria to degrade neutrophil DNA and break down NET's to escape phagocytosis
Term
What does the DNA Hydrolysis Test test for?
Definition
The presence of DNases
Term
Clearing around bacterial colonies in a DNA Hydrolysis test indicates what?
Definition
The presence of DNAses
Term
A negative DNA Hydrolysis test will look like what?
Definition
The blue-green dye media without clearing
Term
What are the predominant causes of dental caries?
Definition
Lactobacillus and streptococcus
Term
What are dental caries?
Definition
Fermentation of dietary sugars by microbes that lead to acid production that wear away tooth enamel and promote decay
Term
What does the Snyder test test for?
Definition
A persons' susceptibility to forming dental caries as a result of the presence of lactobacilli or streptococci
Term
How does the Snyder test select for lactobacilli?
Definition
The pH is reduced to 4.8 - the bacteria are acid-tolerant
Term
A media that changes green to yellow in the Snyder test indicates what?
Definition
The presence of lactobacilli or streptococci.
Term
A change in color after 24 hours indicates what in the snyder test?
Definition
A high susceptibility to dental caries
Term
A change in color after 48 to 72 hours indicates what in the snyder test?
Definition
Moderate to slight susceptibility to dental caries
Term
What does the Kirby-Bauer test test for?
Definition
A microbes susceptibility to an antibiotic.
Term
Which media is used for the Kirby-Bauer test?
Definition
The Mueller-Hinton (MH) agar - pH 7.2-7.4 - beef extract, milk protein, starch.
Term
Why is MH used in the Kirby-Bauer test?
Definition
Has low variation, allows growth of a variety of organisms.
Term
What variables can affect the zone of inhibition in the kirby-bauer test?
Definition
Number of bacterial cells, thickness of the agar and the growth phase of the microorganism.
Term
What phase of growth must the microbe be in during the kirby-bauer test? Why?
Definition
Logarithmic - because this is when they are the most susceptible to antimicrobial agents.
Term
p. aeroginosa is a __________ __________ and is resistant to all antibiotics tested except for ______________
Definition
Gram - Rod, Streptomycin
Term
B. cereus is a ____________ ____________ and is resistant to only ___________ and _____________.
Definition
Gram + Rod, penicillin and trimethoprim
Term
S. aureus is a ________________ _____________ and is resistant to only ______________.
Definition
Gram + rod, chloremphenicol
Term
Where does S. aureus live?
Definition
In the nares of humans
Term
MRSA is resistant to many __________ antibiotics?
Definition
beta-lactam
Term
What does the femB gene encode for?
Definition
The S. aureus-specific enzyme
Term
If MRSA is present in a gel electrophoresis, what will be observed?
Definition
A mark at the femB gene, and mark at the mecA gene and a mark at the 16s rRNA gene
Term
How does a PEA plate inhibit gram negatives?
Definition
Phenylethyl alcohol breaks down the outer membrane and cytoplasmic membrane of gram negatives.
Term
On an MSA plate if the colonies are clear and the background is pink -red.
Definition
Microbes don't ferment mannitol
Term
On an MSA plate if the colonies are clear and the medium turns from red to yellow.
Definition
Microbe ferments mannitol
Term
If a microbe doesn't grow on a PEA plate it is....
Definition
Gram Negative
Term
What is the selective agent in MacConkey Agar?
Definition
Crystal violet and bile salts that inhibit growth of gram pos microorganisms
Term
What are the differential agents in macConkey Agar?
Definition
lactose and PH natural red
Term
On macConkey agar the colonies are mauve on a mauve medium
Definition
Gram negative that doesn't ferment lactose
Term
If a microbe doesn't grow on MacConkey Agar it is....
Definition
gram positive
Term
On macConkey agar, the media color is yellow..
Definition
Ferments lactose
Term
What is the selective agent in HEA?
Definition
Bile salts- prevent gram +
Term
What are the differential agents in HEA?
Definition
carbs and bromophenol blue

and ferric ammonium citrate and sodium thiosulfate
Term
If the media is yellow on HEA agar?
Definition
enteric microbe that ferments carbs
Term
If the colonies are black on HEA agar?
Definition
salmonella!! - produces ferrous sulfide
Term
If a microbe doesn't grow on HE...
Definition
Gram pos
Term
If both OF tubes are yellow..
Definition
The microbe is a facultative aerobe
Term
If an OF tube turns blue
Definition
The microbe may use protein as a fermentation source
Term
An MR test is yellow
Definition
negative for mixed acid fermentation
Term
A MR test is red.
Definition
Positive for mixed acid fermentation - enteric
Term
A VP tube has a little violet at the top
Definition
Positive for butanediol pathway.
Term
A microbe that hydrolyzes starch will look like what?
Definition
zone of clearing around growth- where microbe has eaten at starch
Term
Which antibiotics target protein synthesis?
Definition
chloramphenicol and tetracycline
Term
Which antibiotics prevents bacteria from synthesizing folic acid?
Definition
trimethoprim
Supporting users have an ad free experience!