Identification Of Gram-Positive And Gram-Negative Bacteria

Front 1

What are BAP and CAP?

Back 1

Supportive media (allow growth of all except the most fastidious organisms)

Front 2

How does CAP differ from BAP?

Back 2

The RBCs of CAP have been lysed

Front 3

Two examples of bacterial genera that grow on CAP but not BAP

Back 3

Neisseria

Haemophilus

Front 4

How is BAP useful for bacterial identification?

Back 4

Certain bacteria exhibit hemolytic properties on BAP

Front 5

What are the three hemolysis patterns, and how do they appear on BAP?

Back 5

α - partial hemolysis (greenish zone around isolated colonies)

β - total hemolysis (clear zone around isolated colonies)

γ - no hemolysis

Front 6

Selective medium (Definition)

Back 6

A medium that contains inhibitory reagents that restrict growth of some or most organisms and allow selective growth of desired organisms

Front 7

Differential medium (Definition)

Back 7

A medium that contains a factor or factors that reveal specific metabolic or cultural characteristics of specific bacterial isolates

Front 8

Characteristics of Colistin-Nalidixic Acid (CNA) agar

Back 8

Selective for Gram-positive bacteria

Differential for hemolytic properties

Front 9

Characteristics of MacConkey (Mac) agar

Back 9

Selective for Gram-negative bacteria

Differential for lactose fermentation

Front 10

Describe the appearance of lactose-fermenting bacteria on a MacConkey agar

Back 10

Light pink to reddish colonies surrounded by a zone of precipitated bile

Front 11

What test is used to further differentiate Gram-positive cocci?

Back 11

Catalase test

Front 12

Which Gram-positive cocci are catalase-positive?

Back 12

Staphylococci

Front 13

Which Gram-positive cocci are catalase-negative?

Back 13

Streptococci and Enterococci

Front 14

Describe the appearance of a positive catalase test

Back 14

Bubbling (effervescence) is observable

Front 15

Describe the appearance of a negative catalase test

Back 15

No bubbles

Front 16

Is this catalase test positive or negative?

Back 16

Negative

Front 17

Is this catalase test positive or negative?

Back 17

Positive

Front 18

Which test is used for further identification of the staphylococci?

Back 18

Coagulase test (latex agglutination test)

Front 19

Which of the staphylococci is coagulase-positive?

Back 19

Staphylococcus aureus

Front 20

Which of the staphylococci are coagulase-negative?

Back 20

Staphylococcus epidermidis

Staphylococcus saprophyticus

Front 21

Describe the appearance of a positive coagulase latex agglutination test

Back 21

Aggregation of the black latex suspension with loss of the black background

Front 22

Describe the appearance of a negative coagulase latex agglutination test

Back 22

Little or no agglutination without loss of the black background

Front 23

Is this coagulase latex agglutination test positive or negative?

Back 23

Positive

Front 24

Is this coagulase latex agglutination test positive or negative?

Back 24

Negative

Front 25

How can S. aureus be distinguished from the coagulase-negative staphylococci without a coagulase test?

Back 25

S. aureus is β-hemolytic

S. epidermidis and S. saprophyticus are γ-hemolytic

Front 26

How are the coagulase-negative staphylococci further differentiated?

Back 26

Novobiocin susceptibility test

Front 27

Which coagulase-negative staphylococcus is novobiocin susceptible?

Back 27

S. epidermidis

Front 28

Which coagulase-negative staphylococcus is novobiocin resistant?

Back 28

S. saprophyticus

Front 29

Based on this novobiocin susceptibility test, identify the bacteria on the left and right halves of the agar

Back 29

Left - S. epidermidis

Right - S. saprophyticus

Front 30

Which test is used for further identification of the streptocococci?

Back 30

Hemolysis on blood agar

Front 31

Which streptococci are β-hemolytic?

Back 31

Group A streptococci

Group B streptococci

Front 32

Which streptococci are α-hemolytic?

Back 32

Group D streptococci

Viridans streptococci

Streptococcus pneumoniae

Front 33

Which streptococci are γ-hemolytic?

Back 33

Group B streptococci

Group D streptococci

Enterococcus faecalis (not actually a streptococcus)

Front 34

What type of streptococci are on this agar?

Back 34

γ-hemolytic streptococci

Front 35

What type of streptococci are on this agar?

Back 35

α-hemolytic streptococci

Front 36

What type of streptococci are on this agar?

Back 36

β-hemolytic streptococci

Front 37

How are the β-hemolytic streptococci further differentiated?

Back 37

Latex agglutination test for Group A or Group B

Front 38

Describe the appearance of a positive reaction in the latex agglutination test for Group A or Group B

Back 38

Agglutination of the blue latex with loss of the blue background

Front 39

Describe the appearance of a negative reaction in the latex agglutination test for Group A or Group B

Back 39

Uniform blue, milky appearance

Front 40

The Group A latex reagent was applied to the circle on the left, and the Group B latex reagent was applied to the circle on the right. Identify the bacteria being tested.

Back 40

Group B streptococci

Front 41

How are the γ-hemolytic streptococci further differentiated?

Back 41

Group B latex agglutination test followed by bile-esculin slant and the BHI-6.5% NaCl test

Front 42

Which streptococci return a positive bile-esculin test?

Back 42

Group D streptococci

Enterococcus faecalis

Front 43

Describe the appearance of a positive bile-esculin test

Back 43

Blackening of the bile-esculin agar

Front 44

Describe the appearance of a negative bile-esculin test

Back 44

Yellow/amber agar

Front 45

Which of these bile-esculin slants is positive?

Back 45

Right

Front 46

How are Group D streptococci and Enterococcus faecalis differentiated?

Back 46

BHI-6.5% NaCl test

Front 47

Which bacterium is capable of growing in BHI-6.5% NaCl?

Back 47

Enterococcus faecalis

Front 48

Describe the appearance of a positive BHI-6.5% NaCl test

Back 48

The culture is turbid (cloudy)

Front 49

Describe the appearance of a negative BHI-6.5% NaCl test

Back 49

The culture is clear

Front 50

Which of these BHI-6.5% NaCl tests is positive?

Back 50

Right

Front 51

Are these bacteria lactose fermenters?

Back 51

Yes

Front 52

Are these bacteria lactose fermenters?

Back 52

No

Front 53

What does "IMViC" stand for?

Back 53

Indole production

Methyl red

Voges-Proskauer

Citrate utilization

Front 54

Describe the appearance of a positive indole production test

Back 54

Culture medium is pink to red

Front 55

Describe the appearance of a negative indole production test

Back 55

Culture medium is lime-green

Front 56

Which of these two indole production tests is positive?

Back 56

Right

Front 57

Describe the appearance of a positive methyl red test

Back 57

Culture is red

Front 58

Describe the appearance of a negative methyl red test

Back 58

Culture is yellow

Front 59

Which of these methyl red tests is positive?

Back 59

Left

Front 60

Describe the appearance of a positive Voges-Proskauer test

Back 60

Top layer of culture is red, rest is yellow

Front 61

Describe the appearance of a negative Voges-Proskauer test

Back 61

Entire culture is yellow

Front 62

Which of the following Voges-Proskauer tests is positive?

Back 62

Right

Front 63

Describe the appearance of a positive citrate utilization test

Back 63

Slanted region is blue, the rest is green

Front 64

Describe the appearance of a negative citrate utilization test

Back 64

Green

Front 65

Which of these citrate utilization tests is positive?

Back 65

Left

Front 66

What does "TSI" stand for?

Back 66

Triple sugar iron test

Front 67

What are the potential results of a TSI test (describe the appearance of each)?

Back 67

K/A - red slant, yellow butt

A/A - yellow throughout

K/K - red throughout

Front 68

Describe the appearance of H₂S production in a TSI test

Back 68

Blackening of the butt and/or slant

Front 69

Describe the appearance of gas (CO₂) in a TSI test

Back 69

Gas bubbles in butt, medium sometimes split

Front 70

Identify each TSI reaction from left to right

Back 70

K/A → A/A → K/K → K/A with H₂S → A/A with gas (CO₂)

Front 71

What does the SIM Deeps test determine?

Back 71

Whether an organism can produce H₂S

Front 72

Describe the appearance of a positive SIM Deeps test

Back 72

Culture medium is black

Front 73

Describe the appearance of a negative SIM Deeps test

Back 73

Culture medium is yellowish

Front 74

Which of these two SIM Deeps tests is positive for production of H₂S?

Back 74

Right

Front 75

Describe the appearance of a positive urease test

Back 75

Color change to magenta

Front 76

Describe the appearance of a negative urease test?

Back 76

No color change (remains light orange)

Front 77

Which of these urease tests is positive?

Back 77

Left

Front 78

Describe the appearance of a positive motility test

Back 78

The edges of the inoculation site appear fuzzy

Front 79

Describe the appearance of a negative motility test

Back 79

The edges of the inoculation site appear sharp

Front 80

Which of these motility tests is positive?

Back 80

Left

Front 81

Describe the appearance of a positive oxidase test

Back 81

Dark purple smear

Front 82

Describe the appearance of a negative oxidase test

Back 82

Colorless smear

Front 83

Which of the slides is oxidase positive?

Back 83

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