Micro Quiz 1 (Biochemical Tests) Flashcards
TSI contains
Glucose, Lactose, Sucrose, amino acids, sulfur source, red for alkaline/yellow for acid
TSI results A/A
Yellow slant/yellow butt Glucose fermented, Lactose/Sucrose fermented
TSI results K/A
Red slant/yellow butt Glucose fermented, Lactose/Sucrose not fermented
TSI results K/K
No sugars fermented
TSI has black precipitates in butt
H2S production
TSI has gas bubbles
Gas production
LIA contains
Glucose, amino acids, sulfur source, purple for alkaline/yellow for acid
LIA results K/K
Purple slant/purple butt Lysine decarboxylation
LIA results K/A
Purple slant/yellow butt No enzymatic rxn, only glucose fermentation
LIA results R/A
Red slant/yellow butt Lysine deamination
LIA has black precipitates in butt
H2S production
MIO contains
Glucose, amino acids, no sulfur source, purple for alkaline/yellow for acid
MIO results I+
Indole After adding Kovacs reagent, develops red color, indole was produced
MIO results M+
Motility Media is turbid, can’t see innoculation stab
MIO results O+
Ornithine Decarboxylates ornithine, alkaline conditions, purple color
Biochemical reactions categories
-Single enzyme test -Test for metabolic pathway -Utilization of single substrate -Growth in presence of inhibitory substance
Single enzyme tests
Catalase Coagulase Oxidase Indole Urease PYR
Catalse test
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
Coagulase test
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
Oxidase test
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
Indole test
Looks for tryptophanse enzyme, produces indole Anaerobes use blue-green positive indicator, enterics and non-fermenting GNRs use pinkish red
pH indicators: Bromcresol purple Bromophenol blue Neutral red Phenol red
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
Urease test
Urease hydrolyzes urea to ammonia and CO2, raises pH
Slant becomes purple/pink from phenol red becoming alkaline
PYR test
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
Metabolic pathway tests:
Oxidation and fermentation tests (carb fermentation or OF assays), amino acid degradation, glucose metabolism
Carbohydrate fermentation test
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)
Amino acid degradation test
Decarboxylate, dehydrolyze, or deaminate amino acid Differentiate between, Proteus/Morganella/Providencia from other Enterobacteriaceae
Glucose metabolism (MRVP)
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
Utilization of single substrate test
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
Tests for ability to grow in inhibitory substances
High salt concentration, bile medium with esculin, optochin, antimicrobials, novobiocin
Salt tolerance test
6.5% NaCl (normal is 0.85%)
Halophilic (Enterococcus) is pos
Turns media turbid, produces acid (pH indicator)
Bile esculin hydrolysis test
Positive rxn, turns media from caramel to black from tip to bottom
Optochin sensitivity test
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
Vancomycin resistance
Distinguish between most Gram pos (susceptible) and Gram neg (resistant)
Novobiocin resistance
Gram pos, catalse pos, coagulase neg organisms tested
Screen for Staphylococcus saprophyticus (UTI pathogen) which is resistant
Haemophilus spp. test
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
CAMP test
Beta hemolytic strep only (PYR neg) Group B strep produce CAMP factor, synergistic with S. aureus beta lysin, enhanced hemolysis on sheep blood agar
Motility test
Best at room temp (some species motile at RT and no at higher temps)
Look for turbid media and blurred stab sites
