Micro Lab 2

Front 1

What is the bacitracin test used for?

Back 1

to differentiate beta hemolytic group A strep from other beta hemolytic strep

Front 2

In the bacitracin test, inhibition of bacterial growth will appear as what?

Back 2

a clearing on the agar plate

Front 3

What is the cell target of bacitracin?

Back 3

the cell wall

Front 4

In the bacitracin test, a zone of clearing 10 mm or greater indicates what?

Back 4

bacitracin susceptibility

Front 5

What is the novobiacin test most frequently used for?

Back 5

to differentiate coagulase negative staph and identify novobiocin resistant staph (UTI causer)

Front 6

In the novobiacin test, inhibition of bacterial growth will appear as what?

Back 6

a large clearing around the disk.

Front 7

In the novobiacin test, a zone of clearing 16 mm or greater indicates what?

Back 7

susceptibility

Front 8

Why is Staphylococcus saprophyticus significant?

Back 8

it causes UTIs in females and it is resistant to novobiocin

Front 9

What is the coagulase test used for in the lab?

Back 9

differentiate staph aureus from other Gram positive cocci

Front 10

What advantage does coagulase production provide to a bacterium?

Back 10

it works with normal serum to form fibrin barriers around the bacteria so that they will be shielded from phagocytosis and other types of attack.

Front 11

What are the two forms of coagulase?

Back 11

Tube test or slide test

Front 12

What type of coagulase test did we perform in lab?

Back 12

tube test

Front 13

What was the fluid used in the coagulase test?

Back 13

rabbit plasma

Front 14

what is an advantage of the tube test?

Back 14

it detects the presence of either bound or free coagulase while the slide only tests for bound

Front 15

What was a positive result for the coagulase test performed in the lab?

Back 15

thickening or formation of fibrin threads

Front 16

What is the definition of carbohydrate fermentation?

Back 16

a metabolic process by which an organic molecule acts as an electron donor and one or more of its organic products acts as the final electron acceptor.

Front 17

Carbohydrate fermentation tests are especially useful for differentiating what major group of bacteria?

Back 17

gram negative bacilli like enterobacteriaceae

Front 18

What role does the phenol red play in phenol red broth?

Back 18

turns yellow if the pH is below 6.8 and pink if it is above 7.4 and red if it is in between

Front 19

What is the purpose of the Durham tube in the phenol red broth?

Back 19

it traps gas so we can see a bubble indicative of fermentation

Front 20

Why is reading a phenol red broth test after 18 hours of incubation not recommended?

Back 20

because of the possibility of reversion :when the organism switches metabolic modes from fermentation to deamination after the exhaustion of carbohydrate

Front 21

What is reversion?

Back 21

a shift from acid to alkaline because the carbohydrate is exhausted and the organism goes from fermentation to deamination.

Front 22

A yellow color in phenol red broth indicates what medium component has been fermented?

Back 22

the carbohydrate

Front 23

A yellow color in phenol red broth indicates what medium pH?

Back 23

below 6.8

Front 24

A pink color in phenol red broth indicates what medium component has been catabolized?

Back 24

the peptone amino acids

Front 25

A pink color in phenol red broth indicates what medium pH?

Back 25

above 7.4

Front 26

SIM medium is defined broadly as what type of medium?

Back 26

a combination medium:a medium which allows multiple tests to be performed in one unit

Front 27

What are the 3 test performed by SIM medium?

Back 27

sulfur reduction test, indole production test and the motility test

Front 28

What does a black precipitate in the butt of a SIM tube indicate?

Back 28

is an indication of sulfur reduction and is a positive test

Front 29

What does growth only along the inoculum path of a SIM tube indicate?

Back 29

that it is positive for motility

Front 30

What does hazy growth throughout the SIM medium indicate?

Back 30

maybe the presence of ttc??

Front 31

What does a pink color in Kovac’s reagent added to a SIM tube indicate?

Back 31

a positive reaction and the presence of tryptophanase

Front 32

In terms of oxygen environments, what type of environment does H2S production indicate

Back 32

anaerobic activity

Front 33

What is the Snyder test used for?

Back 33

measure dental carries (tooth decay) susceptibilty caused by lactobacilli and oral strep

Front 34

What two groups of oral bacteria does the Snyder medium select for?

Back 34

lactobacilli and oral strep

Front 35

What does a positive Snyder test look like?

Back 35

a yellow color

Front 36

What is the selective property of the Snyder medium

Back 36

a low pH adjusted to 4.8

Front 37

What do bile salts do to Streptococcus pneumoniae cells?

Back 37

causes them to lyse

Front 38

What was the commercial name of the compound used in the disks used to identify S. pneumoniae?

Back 38

optochin

Front 39

What type of hemolysis does S. pneumoniae produce?

Back 39

alpha hemolysis

Front 40

What is the Gram reaction of S. pneumoniae

Back 40

gram positive

Front 41

What is the purpose of the semi-quantitative urine culture?

Back 41

determine the concentration of bacteria in a urine sample

Front 42

What type of loop is used for a urine culture?

Back 42

a volumetric loop

Front 43

What two sizes of loops are available for performing urine cultures?

Back 43

.001mL and .01mL

Front 44

Why do you streak at a 90o angle to the original streak line?

Back 44

to evenly disperse the bacteria over the entire plate

Front 45

Why would your order this test for one of your patients? (This answer is not in the book).

Back 45

to test for a UTI

Front 46

What is the β-lactamase test used for?

Back 46

to identify if patient isolates are resistant to penicillins and cephalosporins

Front 47

For what bacteria is the β-lactamase test especially useful?

Back 47

resistant strands of neisseria ghonorrhoeae, staph spp,. and members of genus enterococcus

Front 48

What is the molecular mode of action of β-lactam antimicrobials?

Back 48

they interfere with bacteria cell wall synthesis

Front 49

What is the molecular mode of action of β-lactamase?

Back 49

it hydrolyzes the beta lactam ring of the antibiotic

Front 50

β-lactamase disks are impregnated with what antimicrobial?

Back 50

nitrocefin (a cephalosporin)

Front 51

What does a positive β-lactamase test look like?

Back 51

a pink spot on the disk

Front 52

In the antimicrobial agar disk diffusion test, what are the two reasons for incubating the plate once the test has been set up?

Back 52

to allow growth of bacteria and time for the agent to diffuse into the agar

Front 53

Why are all the aspects of the antimicrobial agar disk diffusion test standardized?

Back 53

to ensure reliable results

Front 54

In the antimicrobial agar disk diffusion test, what will you observe if the tested organism is susceptible to an antimicrobial?

Back 54

a clear zone around the disk

Front 55

What does the acronym “MIC” stand for?

Back 55

minimum inhibitory concentration

Front 56

What component of the assay is attached to the latex beads?

Back 56

antigen or antibody

Front 57

What is the marker for detecting the antigen-antibody reaction?

Back 57

agglutination (clumps)

Front 58

What is a positive test in the latex agglutination test?

Back 58

clumping of latex

Front 59

What is a negative test in the latex agglutination test?

Back 59

no clumping

Front 60

What are latex agglutination tests used for in the clinical laboratory?

Back 60

to detect pathogen specific antigens and id some bacterial isolates like Staph aureus