Identification Procedures Flashcards
Motility Tests
Wet prep
Hanging drop
How do you prep a wet prep?
A moderately heavy suspension of bacteria is made in a few mls of nutrient broth and incubated for 2-3 hours.
Place a loopful of culture on a slide and examine on high dry objective lens
What are you looking for on a wet prep
Bacterial motility vs Brownian movement
Brownian movement
The random motion of a particle as a result of collisions with surrounding gaseous molecules
Hanging Drop
A drop of liquid suspended from a cover glass usually placed over the cavity of a depression slide and containing microorangisms or cells
What is so special about the slides that are being used?
They have a concave area that allows the liquid to suspend in order to view motility
What does the motility media allow?
The motile bacteria to diffuse out into the medium for detection of motility of bacteria
How do you do a motility test?
First tube is incubated at 37 degrees celsius
Second tube is incubated at room temperature
What does non-motile bacteria look like after the tests?
Growth is restricted to the stab inoculation line
What does motile bacteria look like after the test?
Diffuse growth throughout the medium
When do you use a motile test?
If organisms are nonmotile on microscopic examination
Catalase Test
Used to determine whether a gram-positive cocci is a staphylococci or streptococci
Positive Catalase Test
Bubbles after adding 3% hydrogen peroxide to slide
What bacteria comes up positive on a Catalase Test?
Staphylococci
Negative Catalase Test
No bubbles
What bacteria come up on a negative catalase test
Streptococci
Coagulase Test
Differentiates coagulase positive Staph and coagulase negative Staph
What are coagulase positive bacteria
Staphylococcus aureus
Staphylococcus pseudointermedius
What are coagulase negative bacteria
Staphylococcus epidermidis
Staphylococcus saprophyticus
Slide coagulase
Detects surface bound coagulase or clumping factor
What does a positive tube coagulase look like
A clot formation
What bacteria comes up positive on a tube coagulase test?
Staphylococcus aureus
Which enzyme coagulates plasma
Coagulase
Oxidase Activity
The oxidase test identifies organisms that produce the enzyme cytochrome oxidase
What bacteria does the Oxidase activity test differentiate
Escherichia coli vs Pseudomonas aeruginosa
What does a positive oxidase test look like?
Microorganisms are oxidase positive when the color changes within 15 to 30 seconds
What bacteria does a positive oxidase test indicate?
Pseudomonas aeuriginosa
What does a negative oxidase activity test indicate?
Escherichia coli
No color change
For the oxidase activity test, what must be present in the bacteria?
Cytochrome Oxidase enzyme
Why would you get a false positive oxidase activity test?
Because you did not use oxidase reagent that was still clear, or you read your test too quickly once you had performed it
Gram positive cocci
Catalase negative
Streptococcus spp
Staphylococcus epidermidis
Gram positive cocci
Catalase positive
Coagulase negative
“Golden staph”
Gram positive cocci
Catalase positive
Coagulase positive
Staphylococcus aureus
Gram negative bacilli
Oxidase positive
Pseudomonas aeruginosa
Gram negative bacilli
Oxidase negative’
Escherichia coli
Acid Production for Glucose
For fastidious organisms
California Mastitis Test
Helps confirm the presence of subclinical mastitis
Uses milk, a reagent, and a paddle
What are the most common organisms found in the milk?
S. aureus Streptococcus agalactiae Streptococcus uberis E. coli Corynebacterium spp Pseudomonas aeruginosa
