Lab Exam 1

Question 1

why do we label plate media on the agar (bottom) side of the plate

Answer 1

• allows us to see the specimen information while looking at the plate in its proper storage orientation
• lids can be switched between plates

Question 2

why do we incubate and store plate media with the agar side up (lid side down)

Answer 2

• Condensation dripping disrupts the streaking pattern and cause isolated colonies to merge together

Question 3

What is the genetic relationship between the cells in a single bacterial colony?

Answer 3

• clones
• Each individual bacterial colony is assumed to have arisen from a single bacterial cell deposited on the agar at that spot.

Question 4

How is this genetic relationship important for downstream clinical identification procedures?

Answer 4

all bacteria in one colony will have identical morphological and physiological characteristics in our downstream identification procedures

Question 5

Which part of slide preparation takes the longest?

Answer 5

making the smears on the slides because of the air-drying step.

Question 6

Staphylococcus aureus colony size

Answer 6

small to med

Question 7

Staphylococcus aureus colony elevation

Answer 7

raised/slightly convex

Question 8

Staphylococcus aureus colony consistency/ surface

Answer 8

smooth, dull, opaque

Question 9

Staphylococcus aureus colony form/shape/margin

Answer 9

round/entire margin

Question 10

Staphylococcus aureus colony color

Answer 10

grayish cream color, yellow tinge

Question 11

Staphylococcus aureus colony hemolysis

Answer 11

beta-hemolysis

Question 12

Staphylococcus saprophyticus colony size

Answer 12

small

Question 13

Staphylococcus saprophyticus colony elevation

Answer 13

raised/ slightly convex

Question 14

Staphylococcus saprophyticus colony consistency/surface

Answer 14

slightly mucoid, shiny, opaque

Question 15

Staphylococcus saprophyticus colony form/shape/ margin

Answer 15

round, entire margin

Question 16

Staphylococcus saprophyticus colony color

Answer 16

white (often bright)

Question 17

Staphylococcus saprophyticus colony hemolysis

Answer 17

non-hemolytic

Question 18

selective component(s) of the MSA plate

Answer 18

7.5% NaCl

Question 19

what species of Staphylococcus was able to grow on the MSA plate

Answer 19

all staphylococci species are able to grow on MSA plates

Question 20

differential component(s) of the MSA plate

Answer 20

the mannitol sugar and the phenol red indicator dye

Question 21

Which species of Staphylococcus was able to ferment the sugar and what species of Staphylococcus was not able to ferment the sugar?

Answer 21

S. aureus can ferment mannitol while S. saprophyticus cannot ferment mannitol.

Question 22

Which tests that you performed in the lab gave the same results for both Staphylococcus species?

Answer 22

the Gram stain (gram-positive cocci in clusters)
the catalase test (positive)
the oxidase test (negative)
the ability to grow on MSA (evident bacterial growth on the plate)

Question 23

What are the expected Gram stain results for staphylococci? arrangement?

Answer 23

gram-positive cocci that show a clustering arrangement

Question 24

Corynebacterium diphtheriae colony size

Answer 24

small

Question 25

Corynebacterium diphtheriae colony consistency/surface

Answer 25

slightly dry

Question 26

Corynebacterium diphtheriae colony form/shape/margin

Answer 26

round/slightly convex/entire margin

Question 27

Corynebacterium diphtheriae colony color

Answer 27

cream/off-white

Question 28

Corynebacterium diphtheriae colony hemolysis

Answer 28

weak beta hemolysis

Question 29

Pseudomonas aeruginosa colony size

Answer 29

medium to large

Question 30

Pseudomonas aeruginosa colony consistency/ surface

Answer 30

silver metallic sheen that is very distinctive

Question 31

Pseudomonas aeruginosa colony form/shape/margin

Answer 31

irregular, flat, slightly spreading, may be unbonate

Question 32

Pseudomonas aeruginosa colony color

Answer 32

sliver/metallic | dense grown may be greenish

Question 33

Pseudomonas aeruginosa colony hemolysis

Answer 33

weak beta hemolysis

Question 34

selective component(s) of the MAC plate

Answer 34

are bile salts and Crystal violet dye

Question 35

What component(s) of the MAC medium inhibits gram-positive organisms?

Answer 35

bile salts and Crystal violet dye

Question 36

differential component(s) of the MAC plate

Answer 36

sugar lactose and the indicator dye neutral red

Question 37

Based on the KIA results, which sugar(s) can P. aeruginosa ferment?

Answer 37

neither glucose nor lactose

Question 38

Based on the KIA results, which sugar(s) can C. diphtheriae ferment?

Answer 38

glucose but not lactose

Question 39

Gram stain results for C. diphtheriae? shape? arrangement?

Answer 39

gram-positive rods with a characteristic “club” shape a “palisade” arrangement

Question 40

Gram stain results for P. aeruginosa? arrangement?

Answer 40

gram-negative rods | "kissing” arrangement

Question 41

what equipment is used for a sterile workspace

Answer 41

laminar flow hoods

Question 42

what equipment provides a sterile bench top

Answer 42

Bunsen burner

Question 43

what can be used instead of a Bunsen burner to sterilize loops/needles

Answer 43

incinerator

Question 44

true or false: antibiotics can turn a non-selective medium into a selective medium

Answer 44

true

Question 45

what do selective media contain that inhibits some bacteria from growing

Answer 45

antibiotics dye chemical agents

Question 46

what is differential media based on

Answer 46

bacteria growth characteristics

Question 47

what are the differential characteristics of a blood agar plate

Answer 47

colony characteristics | hemolysis pattern

Question 48

what is the cell wall composed of

Answer 48

peptidoglycan

Question 49

what kind of bacteria has a thick cell wall

Answer 49

gram +

Question 50

what kind of bacteria have a thin cell wall

Answer 50

gram -

Question 51

where is the cell wall in gram + organisms

Answer 51

outside the cytoplasmic mmb

Question 52

where is the cell wall in gram neg organisms

Answer 52

between the inner cytoplasmic mmb and an outer mmb

Question 53

what kind of bacteria stain purple

Answer 53

gram +

Question 54

what kind of bacteria stain red

Answer 54

gram -

Question 55

true or false: gram stain is dependable on starved or weakened bacteria

Answer 55

false

Question 56

what is the most important step of the gram stain process

Answer 56

decolorization

Question 57

catalase function

Answer 57

decomposes hydrogen peroxide into O2 and water

Question 58

purpose of the catalase test

Answer 58

to tell if a bacteria have the enzyme catalase

Question 59

purpose of the oxidase test

Answer 59

determines if bacteria contain the enzyme cytochrome c oxidase

Question 60

function of cytochrome c oxidase

Answer 60

aerobic respiration