Exam 3 Objectives

Question 1

Where can you find S. epidermis?

Answer 1

In the normal skin microbiota.

Question 2

Where can you find S. saprophyticus?

Answer 2

In the normal vaginal microbiota.

Question 3

What infections can S. saprophyticus cause?

Answer 3

UTIs

Question 4

What infections can S. aureus cause?

Answer 4

MRSA, impetigo, food poisoning, toxic shock syndrome.

Question 5

What is differential media?

Answer 5

Media that changes its appearance due to some characteristic of the organism.

Question 6

What are some examples of differential media?

Answer 6

Fermentation tubes or DNase agar.

Question 7

What is selective media?

Answer 7

Media that encourages some growth while inhibiting others

Question 8

What is an example of selective media?

Answer 8

CNA-BA

Question 9

Why is CNA-BA considered selective and differential?

Answer 9

The antibiotics, colistin and nalidixic acid (CNA) inhibit the growth of Gram-negative organisms making Columbia CNA selective as well as differential.

Question 10

What does a catalase test do?

Answer 10

Tests for the enzyme catalase which breaks down hydrogen peroxide into water and oxygen.

Question 11

Why is catalase important?

Answer 11

Hydrogen peroxide is a toxic form of oxygen and a byproduct of aerobic respiration; bacteria need some way to break it down.

Question 12

What does a positive test for catalase look like?

Answer 12

When hydrogen peroxide is put on the organism, a vigorously bubbling will occur.

Question 13

Do Staphs or Strepts test positve for coagluase?

Answer 13

Staphs

Question 14

What does a coagulase test do?

Answer 14

Tests to see if blood plasma can be turned into a blood clot by coagulase.

Question 15

Why are blood clots important for bacteria?

Answer 15

Clots can help bacteria establish infections and protect themselves.

Question 16

What media was used for the coagulase test?

Answer 16

Rabbit plasma.

Question 17

What does a positive coagulase test look like?

Answer 17

A clot will be formed in the test tube.

Question 18

What does a Novobiocin Disk test do?

Answer 18

Test how sensitive or resistant Staphs are to the antibiotic Novobiocin.

Question 19

How can we tell is a Staph is resistant or sensitive to Novobiocin?

Answer 19

Sensitive: large zone of inhibition.
Resistant: small zone of inhibition.

Question 20

How do you perform a Novobiovin Disk test?

Answer 20

Create a lawn of bacteria.
Put the antibiotic disk in the middle.

Question 21

What oxygen classifications do more Strepts belong in?

Answer 21

Most are facultative anerobes or anerobes.

Question 22

What is a capnophile?

Answer 22

An organism that grows better in a high concentration of CO2.

Question 23

What do we do to accommodate some Strepts being capnophiles?

Answer 23

We grow the Strepts in a candle jar to raise the concentration of CO2.

Question 24

What are some infections S. pyogenes cause?

Answer 24

Strept throat (which can turn into scarlet fever), impetigo, necrotizing fascitis, autoimmune complications, and rheumatic fever (which can lead to heart valve damage).

Question 25

Where can S. agalactiae be found?

Answer 25

In the normal microbiota vaginally ~30%

Question 26

What infections can S. agalactiae cause?

Answer 26

Neonatal meningitis.

Question 27

What infections can S. agalactiae cause?

Answer 27

Neonatal meningitis.

Question 28

What infections can S. pneumoniae cause?

Answer 28

Pneumonia, ear infections, and meningitis.

Question 29

What infections can S. mitis cause?

Answer 29

Tooth decay and plaque.

Question 30

Where can S. mitis be found?

Answer 30

Normal mouth microbiota.

Question 31

What is specifc about S. mitis and S. pneumoniae?

Answer 31

The both can make a capsule for protection.

Question 32

Where can Enterococcus faecalis be found?

Answer 32

In the normal microbiota of the large intestine.

Question 33

What are Lancefield groups based on?

Answer 33

They are based in the carbohydrate surface antigens of Strept.

Question 34

What does B-hemolysis do?

Answer 34

Lysis all red blood cells.

Question 35

What is O hemolysin?

Answer 35

Inhibited by oxygen.

Question 36

What is S hemolysin?

Answer 36

Stable in oxygen.

Question 37

What does Alpha-hemolysis do?

Answer 37

Partial red blood cell lysis.

Question 38

What does Gamma-hemolysis do?

Answer 38

No red blood cell lysis.

Question 39

How do B-hemolysis bacteria look on blood agar?

Answer 39

The media becomes clear or yellow especially around the stabs in the agar.

Question 40

How do Alpha-hemolysis bacteria look on blood agar?

Answer 40

The media becomes greenish/brown especially around the stabs in the agar.

Question 41

How do Gamma-hemolysis bacteria look on blood agar?

Answer 41

The media does not change color or appearance.

Question 42

How did we innoculate a bile esculin test?

Answer 42

We innoculate the slant just like normal.

Question 43

What are we testing for in a bile esculin test?

Answer 43

Testing to see if the organism can break down the polysaccharide esculin into esculatin and glucose.

Question 44

What group of Strepts test positive for a bile esculin test?

Answer 44

Group D Strepts.

Question 45

What does a positive bile esculin look like?

Answer 45

A black color change will occur.

Question 46

How did we innoculate a hippurate test?

Answer 46

Inoculate the solution like normal.

Question 47

What are we testing for in a hippurate test?

Answer 47

We testing to see if an organism can use hippurate hydrolase to break down hippurate into benzoate and glycine.

Question 48

What group of Strepts test positive for the hippurate test?

Answer 48

Group B Strepts.

Question 49

What reagent do we add to hippurate tests after incubation?

Answer 49

Ninhydrin.

Question 50

What does a positive hippurate test look like?

Answer 50

A purple color change occurs.

Question 51

Why is MacConkey agar both differential and selective?

Answer 51

MacConkey agar contains both bile salts and lactose which acts both selectively and differentially. This bile salt component is selective to gram-negative enteric bacteria, and inhibits the growth of most gram-positive bacteria.

Question 52

What tests make up the MIViC tests?

Answer 52

Indole test, Methyl Red test, Voges-Proskauer test, and Citrate test.

Question 53

What media did we use in the indole test?

Answer 53

We used tryptophan enriched broth.

Question 54

What are we testing for in an indole test?

Answer 54

Tests if tryptophanase can break down tryptophan into indole, pyruvate, and NH3.

Question 55

What is indole?

Answer 55

Indole is an amino acid.

Question 56

What reagent do we add to an indole test after incubation?

Answer 56

Kovac's reagent.

Question 57

What does a positive indole test look like?

Answer 57

A red ring is sitting on top of the media after the reagent is added.

Question 58

What are we testing in a methyl red test?

Answer 58

Tests if the organism uses the mixed acid fermentation path when given glucose.

Question 59

What are mixed acid fermentation pathway products?

Answer 59

Succinic acid, lactic acid, formic acid, acetic acid.

Question 60

What reagent is added after incubation of a methyl red test?

Answer 60

Methyl red, which acts as a pH indicator.

Question 61

What does a positive methyl red test look like?

Answer 61

A red color change occurs.

Question 62

What are we testing for in a Voges-Proskauer test?

Answer 62

If the organism produces acetoin, which breaks down into 2,3 butanediol which has a pH of 6.

Question 63

What reagent is added to a Voges-Proskauer after incubation?

Answer 63

Voges-Proskauer A and B in a 3:1 ratio.

Question 64

What does a positive Voges-Proskauer test look like?

Answer 64

A dark/muddy red color change.

Question 65

What are we testing in a citrate test?

Answer 65

Tests if an organism can break citrate into NH3 using citrase.

Question 66

What pH indicator is in the slant?

Answer 66

Brothymol blue.

Question 67

What does a positive citrate test look like?

Answer 67

A blue color change (blue signifies that the media has turned alkaline).

Question 68

What's special thing do we have to do to the cap of citrate and urea tests?

Answer 68

Leave it loose to let in oxygen.

Question 69

What are we testing for in a urea test?

Answer 69

Tests if organism can use urease to break down urea into 2 NH3 + CO2.

Question 70

What is formed if 2 NH3 + CO2 is combined with water?

Answer 70

Ammonium carbonate (NH4)2CO3 which is basic.

Question 71

What pH indicator is in the slant?

Answer 71

Phenol red.

Question 72

What does a positive urea test look like?

Answer 72

A pink alkaline color change.

Question 73

What does the Kliger's Iron Agar (KIA) test for?

Answer 73

Sugar utilization and hydrogen sulfide production.

Question 74

What does the KIA agar contain to test for sugar utilization?

Answer 74

0.1% glucose, 1% lactose, and the pH indicator phenol red.

Question 75

How are the acidic and basic colors shown in the slant?

Answer 75

Acidic=Yellow Basic=Red

Question 76

What components of the KIA agar test for hydrogen sulfide?

Answer 76

Sodium thiosulfate (a source of sulfur) and ferric ammonium citrate (tests for hydrogen sulfide production).

Question 77

How does ferric ammonium citrate show hydrogen sulfide production?

Answer 77

The hydrogen sulfide reacts with the iron to make iron sulfide which shows as a black ppt.

Question 78

How do we innoculate the KIA slant?

Answer 78

We stab into the shallower butt portion and then streak to get the heaviest inoculum in the butt of the tube (the place with the least oxygen).

Question 79

What does an A/A test result mean?

Answer 79

It means both the slant and the butt were yellow and the organism ferments glucose and lactose.

Question 80

What does a K/K test result mean?

Answer 80

It means both the slant and the butt were red and the organism cannot ferment glucose or lactose.

Question 81

What does a K/A test result mean?

Answer 81

It means the slant was red and the butt was yellow and the organism can ferment glucose but not lactose.

Question 82

What does a black color anywhere in the slant mean?

Answer 82

It means the organism produces hydrogen sulfide.

Question 83

What do creaks or bubbles in the agar mean?

Answer 83

Gas was produced during fermentation.

Question 84

What 3 things do we test in the SIM test?

Answer 84

Hydrogen sulfide production, indole production, and motility.

Question 84

What 3 things do we test in the SIM test?

Answer 84

Hydrogen sulfide production, indole production, and motility.

Question 85

How does a positive SIM test look for hydrogen sulfide production?

Answer 85

A black color change.

Question 86

How does a positive SIM test look for indole production?

Answer 86

A red ring is present when Kovac's reagent is added.

Question 87

How does a positive SIM test look for motility?

Answer 87

The whole tube is cloudy, not just around the stab.

Question 88

How do we innoculate a SIM test?

Answer 88

Stab straight down and up in the media.

Question 89

How do we create a wet mount?

Answer 89

Use a glass pipet to drop a couple of drops onto a glass slide. Put a plastic coverslip over the drops, creating air bubbles.

Question 90

How do we read a wet mount under the microscope?

Answer 90

Find the edge of an air bubble in 4x and focus. Move up to 40x, focus, and look outside the edge of the bubble.