Bacteriology Lab Final

Question 1

Name the dye present in MacConkey Agar that is responsible for staining microbes that ferment lactose

Answer 1

neutral red

Question 2

The catalase test detects the enzyme catalase, which is responsible for converting ____________ to _____________

Answer 2

The catalase test detects the enzyme catalase, which is responsible for converting hydrogen peroxide to water and oxygen

Question 3

Is Staphylococcus aureus catalase positive or catalase negative

Answer 3

Staphylococcus aureus is catalase positive

Question 4

Is Streptococcus equi catalase positive or catalase negative?

Answer 4

Streptococcus equi is catalase negative

Question 5

The oxidase test depends on the presence of _____________ in a bacterial cell

Answer 5

Cytochrome C Oxidase

Question 6

Are most Staphylococcus spp. oxidase positive or oxidase negative?

Answer 6

Most Staphylococcus spp. are oxidase negative

(the negative test is the cue-tip marked ‘B’)

Question 7

In the motility test, tetrazolium salts are added to help detect motility. When the bacterium grows, the dye from the salts is incorporated into the bacterial cells, where it is reduced to an insoluble red pigment.

What is the name of that red pigment?

Answer 7

formazan

Question 8

What is the pH indicator utilized in the urease test?

Answer 8

phenol red

Question 9

What does the Methyl Red (MR) test test for?

Answer 9

Low MW acids like lactic, formic, & acetic acids

Question 10

The citrate test tests for ________________________

What is the indicator used?

Answer 10

ability to use citrate as sole carbon source

Indicator used: Bromothymol blue

Question 11

Does Proteus mirabilis produce a positive or negative motility test?

Answer 11

positive

Question 12

What color will a positive urease test produce?

Answer 12

bright pink

Question 13

Which amino acid is involved in the indole test?

Answer 13

Tryptophan

Question 14

Is Pseudomonas aeruginosa oxidase positive or oxidase negative?

Answer 14

Pseudomonas aeruginosa is oxidase positive

Question 15

Rappaport-Vassiliades Broth is used mainly for which bacterial species?

Answer 15

*Salmonella *spp.

Question 16

Identify these Gram{+] cocci in clusters

Answer 16

Staphylococcus spp

Question 17

Identify these Gram[+] cocci in chains

Answer 17

Streptococcus spp.

(just remember, “strepto” means chain in Greek)

Question 18

Identify these Gram[+], gamma-hemolytic cocci in pairs or short chains

Answer 18

Enterococcus spp.

Question 19

Identify these large aerobic or facultative anaerobic Gram[+] rods that form endospores

Answer 19

Bacillus spp.

Question 20

True or False:

Candida spp. can all produce pseudohyphae

Answer 20

True

If you see pseudohyphae, it’s more than likely Candida spp.

Question 21

Identify these Gram[+] short rods:

Answer 21

Arcanobacterium spp.

Question 22

T/F: MacConkey agar is designed to grow Gram-positive bacteria and differentiate lactose fermenters from non-fermenters

Answer 22

False.

MacConkey agar is designed to grow Gram-negative bacteria and differentiate lactose fermenters from non-fermenters

Question 23

______________ is a differential, selective medium for the isolation of Shigella and Salmonella species from enteric pathological specimens. It contains lactose, sucrose and salicin.

Answer 23

Hektoen enteric agar

Question 24

Between Microsporum spp. and Trichophyton spp., which one is known to have numerous microconidia?

Answer 24

Trichophyton spp.

Question 25

Found in concentrated pigeon droppings due to their hig content of creatinine. Identify.

Answer 25

*Cryptococcus neoformans*

Question 26

Which one of these is *Aspergillus* spp?

Answer 26

That one.

Question 27

Blood Agar is a general purpose enriched medium that is used to differentiate bacteria based on *which properties*?

Answer 27

**hemolytic properties**

Question 28

Lactose-positive organisms display *what color* on MacConkey agar?

Answer 28

**red/pink** lactose fermenters produce acid and lower the pH of the medium, producing red/pink colonies

Question 29

**Hektoen enteric agar** contains indicators of lactose fermentation and H₂S production. What are those indicators?

Answer 29

**thiosulfate** and **ferric ammonium citrate**

Question 30

What are the components of **Hektoen enteric agar** that inhibit growth of Gram-positive organisms?

Answer 30

**bile salts** and **bromothymol blue**

Question 31

What is the **primary stain** used in Gram-staining?

Answer 31

**crystal violet**

Question 32

List the four basic steps in the Gram stain

Answer 32

1. Primary staining (crystal violet) 2. Add a mordant (Gram's iodine) 3. Decolorization (alcohol or acetone) 4. Counterstaining (safranin or fuschin)

Question 33

Gram-positive or Gram-negative?

Answer 33

Gram-positive

Question 34

Gram-positive or Gram-negative?

Answer 34

Gram-negative

Question 35

The image shows *Staphylococcus aureus* colonies surrounded by a zone of complete hemoylsis. Which toxin causes this type of hemoylsis?

Answer 35

alpha-toxin

Question 36

Which one represents a positive catalase test?

Answer 36

Question 37

What is the indicator used in the **Indole test**?

Answer 37

Kovac's Reagent

Question 38

IMViC is a group of individual tests used in differentiating which family?

Answer 38

*Enterbacteriaceae*

Question 39

Identify.

Answer 39

*Staphylococcus* spp.

Question 40

Identify.

Answer 40

*Streptococcus* spp.

Question 41

Identify.

Answer 41

*Enterococcus* spp.

Question 42

Name the three antimicrobial susceptibility tests we discussed in lab:

Answer 42

1. Kirby Bauer 2. E-Test 3. Broth Microdilution

Question 43

Regarding the Kirby Bauer test, does a larger diameter indicate greater antibiotic resistance or less antibiotic resistance?

Answer 43

**Larger diameter = less antibiotic resistance/greater susceptibility** If the zone of inhibition is greater, that indicates that the bacteria is *susceptible* to the antibiotic, not *resistant* to it

Question 44

Which type of agar plate is used in the **Kirby Bauer **test?

Answer 44

**Mueller Hinton** agar

Question 45

The lowest concentration of antimicrobial agent that inhibits bacterial growth/multiplication is known as:

Answer 45

**Minimal Inhibitory Concentration (MIC)**

Question 46

The lowest concentration of antimicrobial agent that allows less than 0.1% of the original inoculum to survive is known as:

Answer 46

**Minimal Bactericidal Concentration (MBC)** or **Minimal Lethal Concentration (MLC)**

Question 47

T/F: The **E-Test** is a quantitative assay for determining MLC

Answer 47

**False.** The E-Test is a quantitative assay for determining **MIC (Minimal Inhibitory Concentration)**, *NOT MLC (Minimal Lethal Concentration)*

Question 48

T/F regarding **MIC**: The lower the MIC, the more susceptible the bacteria is to the antibacterial agent

Answer 48

True

Question 49

What does ELISA stand for?

Answer 49

Enzyme Linked Immunosorbent Assay

Question 50

Regarding Sandwich ELISA, are we testing a sample containing **antigens** or **antibodies**?

Answer 50

**Antigen** For a Sandwich ELISA, the test kit comes coated with antibody. What *we're putting on* as the analyte is the **antigen**

Question 51

\_\_\_\_\_\_\_\_\_\_ are dyes that have the ability to absorb the short wavelength UV radiation and emit light of longer wavelength fluorescence

Answer 51

**_Fluorochromes_** are dyes that have the ability to absorb the short wavelength UV radiation and emit light of longer wavelength fluorescence

Question 52

Which of the following does *not* involve specific antigen-antibody complexes? * PCR * IFA * ELISA * Agglutination

Answer 52

**PCR**

Question 53

What is the 3^rd reagent in the Gram stain?

Answer 53

**alcohol** or **acetone** The 3^rd stage is the *decolorization* stage

Question 54

Does *Klebsiella pneumoniae* have a positive or negative Motility test?

Answer 54

negative

Question 55

What bacteria is metallic green on Eosin-Methylene Blue agar?

Answer 55

*E. coli*

Question 56

T/F: the Kirby-Bauer test is a quantitative assay for determining MIC

Answer 56

**FALSE** The **E-test** is a quantitative assay for determining MIC. The Kirby-Bauer test measures zone of inhibition, but is not a quantitative determinant for MIC

Question 57

What would be the test of choice to differentiate between *Pseudomonas* and *Enterobacteria*?

Answer 57

**Oxidase test** *Pseudomonas* is **_oxidase-positive_**

Question 58

T/F: PCR tests for Antibody interactions

Answer 58

False. PCR tests DNA/RNA sequences

Question 59

Which PCR detects product formation throughout the PCR reaction?

Answer 59

Real-time PCR

Question 60

Which PCR only measures product after the PCR reaction is complete?

Answer 60

End-point PCR

Question 61

Which PCR utilizes agarose gel electrophoresis?

Answer 61

End-point PCR

Question 62

XLD agar is selective and differential for:

Answer 62

Gram-negative enteric bacteria, specifically ***Shigella* and *Salmonella*** * Salmonella* will produce red colonies with black centers * Shigella* will just produce red colonies

Question 63

You see these colonies on XLD agar. What is your diagnosis?

Answer 63

* Salmonella* * Salmonella* will first ferment the xylose creating a temporary acid reaction but this is reversed by the subsequent decarboxylation of lysine with alkaline metabolic products. Superimposed on the red (alkaline) colonies is the production of hydrogen sulfide, so most *Salmonella* have red colonies with a black center.