Micro Quiz 1 (Biochemical Tests)

Question 1

TSI contains

Answer 1

Glucose, Lactose, Sucrose, amino acids, sulfur source, red for alkaline/yellow for acid

Question 2

TSI results A/A

Answer 2

Yellow slant/yellow butt Glucose fermented, Lactose/Sucrose fermented

Question 3

TSI results K/A

Answer 3

Red slant/yellow butt Glucose fermented, Lactose/Sucrose not fermented

Question 4

TSI results K/K

Answer 4

No sugars fermented

Question 5

TSI has black precipitates in butt

Answer 5

H2S production

Question 6

TSI has gas bubbles

Answer 6

Gas production

Question 7

LIA contains

Answer 7

Glucose, amino acids, sulfur source, purple for alkaline/yellow for acid

Question 8

LIA results K/K

Answer 8

Purple slant/purple butt Lysine decarboxylation

Question 9

LIA results K/A

Answer 9

Purple slant/yellow butt No enzymatic rxn, only glucose fermentation

Question 10

LIA results R/A

Answer 10

Red slant/yellow butt Lysine deamination

Question 11

LIA has black precipitates in butt

Answer 11

H2S production

Question 12

MIO contains

Answer 12

Glucose, amino acids, no sulfur source, purple for alkaline/yellow for acid

Question 13

MIO results I+

Answer 13

Indole After adding Kovacs reagent, develops red color, indole was produced

Question 14

MIO results M+

Answer 14

Motility Media is turbid, can’t see innoculation stab

Question 15

MIO results O+

Answer 15

Ornithine Decarboxylates ornithine, alkaline conditions, purple color

Question 16

Biochemical reactions categories

Answer 16

-Single enzyme test -Test for metabolic pathway -Utilization of single substrate -Growth in presence of inhibitory substance

Question 17

Single enzyme tests

Answer 17

Catalase Coagulase Oxidase Indole Urease PYR

Question 18

Catalse test

Answer 18

Decomposes hydrogen peroxide to water and oxygen, immediate vigorous bubbling Differentiate staphylococci (+) and Listeria (+) from streptococci (-) Contamination with RBC’s can cause false pos, culture older than 24 hrs can give false neg

Question 19

Coagulase test

Answer 19

Screening for S. aureus Testing for “clumping factor” on cell wall by adding fibrinogen Confirm slide with tube, look for clot, observe closely first 4 hrs, leave overnight if still neg Slide pos but tube neg suggests S. lugdunensis and S. scheifleri

Question 20

Oxidase test

Answer 20

Test for gram neg organisms, all enterics are neg Add reagent or colonies, look for purple color Stainless steel/nichrome loops cause false pos (use wood, plastic, or platinum), growth from certain media can cause false negs because of indicator colors

Question 21

Indole test

Answer 21

Looks for tryptophanse enzyme, produces indole Anaerobes use blue-green positive indicator, enterics and non-fermenting GNRs use pinkish red

Question 22

pH indicators: Bromcresol purple Bromophenol blue Neutral red Phenol red

Answer 22

Bromcresol purple = yellow at acid/neutral, purple at alkaline Bromophenol blue = yellow at acid/neutral, blue at alkaline Neutral red = red at acid/neutral, yellow at alkaline Phenol red = yellow at acid/neutral, red/pink at alkaline

Question 23

Urease test

Answer 23

Urease hydrolyzes urea to ammonia and CO2, raises pH

Slant becomes purple/pink from phenol red becoming alkaline

Question 24

PYR test

Answer 24

Done on both Gram neg and Gram pos

Turns red withing 5 min for positive

Identify group A strep, differentiate group D strep from Enterococcus

Question 25

Metabolic pathway tests:

Answer 25

Oxidation and fermentation tests (carb fermentation or OF assays), amino acid degradation, glucose metabolism

Question 26

Carbohydrate fermentation test

Answer 26

Test ability to ferment specific sugar

Differentiate between Enterobacteriaceae, glucose fermenters from aerobic pseudomonads and other Gram neg non-fermenters

Red for alkaline (neg), yellow for acid (pos)

Question 27

Amino acid degradation test

Answer 27

Decarboxylate, dehydrolyze, or deaminate amino acid Differentiate between, Proteus/Morganella/Providencia from other Enterobacteriaceae

Question 28

Glucose metabolism (MRVP)

Answer 28

Methyl red, checks for mixed acid production

Voges-proskauer (VP), checks for butylene glycol to diacetyl

Organism will be positve for only one, not both

Positives are red/orange

Question 29

Utilization of single substrate test

Answer 29

Citrate as sole carbon source, starts green, turns blue If able to grow but not change color, still pos

Innoculated lightly so dead colonies aren’t used as carbon source instead

Question 30

Tests for ability to grow in inhibitory substances

Answer 30

High salt concentration, bile medium with esculin, optochin, antimicrobials, novobiocin

Question 31

Salt tolerance test

Answer 31

6.5% NaCl (normal is 0.85%)

Halophilic (Enterococcus) is pos

Turns media turbid, produces acid (pH indicator)

Question 32

Bile esculin hydrolysis test

Answer 32

Positive rxn, turns media from caramel to black from tip to bottom

Question 33

Optochin sensitivity test

Answer 33

Differentiate Streptococcus pneumonia from other alpha hemolytic streptococci that are catalse neg

Looking for zone of inhibition, if zone smaller than standard size check for bile solubility

Question 34

Vancomycin resistance

Answer 34

Distinguish between most Gram pos (susceptible) and Gram neg (resistant)

Question 35

Novobiocin resistance

Answer 35

Gram pos, catalse pos, coagulase neg organisms tested

Screen for Staphylococcus saprophyticus (UTI pathogen) which is resistant

Question 36

Haemophilus spp. test

Answer 36

Small, Gram neg rod only growing on chocolate (not blood*)

Require X (hemin) and/or V (NAD) Add X and V strips to plate, CO2 incubation, see growth around strips needed for growth H. influenzae grows only around XV

If species name starts with para-, most likely needs V

Satalite test, put S. aureus with Haemophilus on blood plate, S. aureus breaks down cells so Haemophilus can use substrates

Question 37

CAMP test

Answer 37

Beta hemolytic strep only (PYR neg) Group B strep produce CAMP factor, synergistic with S. aureus beta lysin, enhanced hemolysis on sheep blood agar

Question 38

Motility test

Answer 38

Best at room temp (some species motile at RT and no at higher temps)

Look for turbid media and blurred stab sites