Micro Exam III

What is used for the catalase assay?

Hydrogen peroxide

What does catalase do?

Degrade H2O2 to O2 and water

What two organisms are known for testing positive for catalase?

Staphylococcus, micrococcus

How does micrococcus differ from staphylococcus?

Staphylococcus is a facultative aerobe and can ferment glucose

Is blood agar selective or differential or both?

Differential

What assay should we use to differentiate Streptococcus and Enterococcus? What are they considered in that assay?

Blood Agar plate; Streptococcus is alpha/beta, enterococcus is gamma

What bacteria species is beta-hemolytic? What bacteria genus is usually alpha-hemolytic in the mouth?

Streptococcus pyogenes, streptococcus

What is the mannitol salt agar selective and differential for?

Selective for halotolerant species, differential for mannitol fermentation

What color is positive mannitol assay?

Yellow

What bacteria ferments mannitol but at a slower rate?

Staphylococcus saprophyticus

What species was positive for fermenting mannitol?

Staphylococcus aureus

What does a positive coagulase assay look like? What species is positive?

Grainy, staphylococcus aureus

What is coagulase?

Protein that interacts with fibrinogen to coagulate blood plasma

What species was resistant to Novobiocin? How long does the zone of inhibition need to be to be resistant?

Staphylococcus saprophyticus, 17mm

What are the four gram positives we worked with? Genus

Micrococcus, staphylococcus, streptococcus, enterococcus

What is the difference between streptococcus and staphylococcus?

Staphylococcus has catalase and is seen in clusters

How does the lysine decarboxylase work?

Inoculate bacteria with oil, glucose is fermented, acids lower pH (yellow), decarboxylase synthesis, cadaverine produced, raises pH (purple)

What bacteria was positive for lysine decarboxylase?

E. coli

What does the oxidative fermentation assay look for?

Fermenting//oxidizing glucose into acids

What is the pH indicator for the O/F assay?

Bromophenol blue

What is an example of a gram negative bacteria that does not ferment sugars that we used the O/F assay for

Pseudomonas

How does Pseudomonas use glucose?

Oxidatively to produce acids, NOT fermentation

What are the positive colors for O/F assay?

Yellow and blue

What genus of bacteria can ferment glucose? These are facultative anaerobes

Enterobacter

What are four bacteria that are coliforms?

Escherichia, enterobacter, klebsiella, citrobacter

What is the MacConkey agar differential for? What does it have to make it differential?

lactose fermentation, lactose and pH indicator neutral red

What bacteria makes a lot of acid from lactose?

E. coli and Citrobacter freundii

What does a positive MacConkey assay look like? Negative?

Bright pink, pale

What does EMB have that makes it selective for gram negatives?

Eosin and methylene blue

What is a MacConkey agar selective for? What does it have that makes it selective?

Gram negative, crystal violet and bile salts

What bacteria ferments lactose but does NOT produce a lot of acid? What will show up if a bacteria does produce a lot of acids?

Enterobacter aerogenes, hazy salt precipitate

What is the EMB plate differential for and why?

Lactose fermenters, lactose and pH indicators eosin and methylene blue

What does a positive result look like for EMB agar? Negative?

Dark purple/metallic green, clear

What does the methyl red assay look for? When is the methyl red indicator added?

Fermentation of glucose into a lot of acids, after incubation

What two species does the methyl red assay distinguish?

E. coli and enterobacter aerogenes

What’s a positive methyl red assay? Negative? Provide pHs

Red (below 4.5) and orange (4.6-5.6) are positive, yellow is negative

What does the citrate assay test for?

If the bacteria can use citrate as their only source of energy through certain enzymes

What is the agar we use for the citrate assay? What is the main ingredient?

Simmons Citrate, sodium citrate

What is a positive and negative result on the citrate assay? give an example bacteria for each

Positive is blue and enterobacter aerogenes and negative is green and E coli

What species are positive for Methyl Red? Large concentrations of acids from glucose

E. coli and proteus vulgaris

What does urease do?

Break down urea into carbon dioxide and ammonia

What genus produces a large amount of urease? What is a positive result?

Proteus, bright pink

What does H2S interact with to make the black color on the SIM assay?

Iron

What are three bacteria that test positive for the Sulfide production assay? (SIM)

Salmonella, proteus, citrobacter

What is the color of a negative sulfide assay? NOT CLEAR

Yellow

What is broken down to form indole? What is added AFTER incubation to extract the indole? What in that makes it interact with indole?

Tryptophan, Kovac’s reagent with butanol

What is a positive result for indole? What is a bacteria that is positive?

Red on top, E. coli

What does a motility assay look for? Don’t say movement.

Flagella

What two species test negative for the motility assay?

Klebsiella and shigella

Why is EnteroPluri good?

Tells us variations in strains

What do entericbacteriacae do?

Ferment glucose and lactose

How long is the EnteroPluri code?

5 digits

What do we test for in water? What makes a bacteria a good indicator? What’s an example for poop contamination?

Indicator species that live in the intestines and when there is more, that means there is more contamination, and not sage in water. E. coli

What are the three series of assays we use to test for coliform bacteria?

Presumptive, confirmed, completed

What does the presumptive test use?

Durham tube with lactose

What is the presumptive test bacteria streaked on? Why?

EMB to test for gram negative and lactose fermentation

What is done with bacteria from a positive confirmed test?

Another lactose broth with durham tube and agar for gram stain