Micro Lab Flashcards
CNS
Coagulase negative staphylococci
S. Epidermidis
A. Saprophyticus
What are the virulence factors if s. Aureus?
Coagulase DNase- digest DNA Hemolysin αtoxin-β hemolysis Pigment staphyloxanthin Ferments mannitol to produce acid
Beta hemolysis
Clear zone in blood agar
Alpha hemolysis
Greenish discoloration
Gamma hemolysis
No effect on blood cells
Group A streptococci
Streptococcus pyogenes
Group B strep
A. Agalactiae
Group C
Zoonoses
A. Dusgalactiae
Fermentation tests
Durham tube sugar fermentation a
Mixed acid fermentation (methyl red test)
2,3 butanediol fermentation (Vogues-Proskauer test)
Citrate test
Durham tubes
Ferment sugar? Acid produced. Maybe gas too. Acid? Red–>yellow. Gas? Displacement of medium from the Durham tube.
Mixed-acid fermentation
Methyl red–> turns red if acid is present some gram negative intestinal bacteria produce a number if organic acids (formic, succinic, lactic, acetic)
Positive result is red. Negative is yellow.
2,3 butanediol fermentation
Voges-Proskauer test
Does a neutral end product 2,3 butanediol exist? Important test for determining within enterobacteriaceae. What is negative for MR will usually be positive for VP provided they are enterobacteriaceae
Positive result is red. Negative is yellow or copper
Citrate test
Organisms that metabolize citrate release ammonia, making the medium a deeper Prussian blue (basic). Green(-)–> blue(+)
Why is it important to do the o/f glucose test before any other of the fermentation tests? Fermentation tests–>MR, VP, Durham tubes, citrate
Oxidase tests–> oxidase, catalase, nitrate
If your organism is only oxidative and not capable if fermenting sugars, don’t do the fermentation tests. Waste of time.
Amylase
Degrade starch
Cellulose
Degrade cellulose
Protease
Degrade protein, casein and gelatin and polypeptides into amino acids
Lipase a
Degrade triglycerides into fatty acids and glycerol
Tryptophanase
Pyruvate and indole
Starch hydrolysis
Bacteria that hydrolyze starch have amylases that degrease the starch molecule into molecules of maltose, glucose, and dextrins.
Clear zone–amylase present, hydrolyzing starch.
Casein hydrolysis
Milk agar
Clear zone means proteolysis of casein.
Fat hydrolysis
Lipases degrade triglycerides into fatty acids and glycerol. Spirit blue agar contains tributyrin, a simple animal triglyceride that serves as a substrate for lipases. Dark blue precipitate, zone of clearing positive
Tryptophan degradation
Bacteria that have the ability to degrade the amino acid tryptophan produce indole, ammonia, and pyruvic acid. (Pyruvic acid is useful to the organism) Kovacs reagent is used to see if degradation of tryptophan has occurred. Kovacs turns red if indole is present.
Urea hydrolysis
Urease–> splits molecule into carbon dioxide and ammonia. Used to seperate out the enteric bacteria proteus, providencia, and morganella. Positive is a beautiful pink color. Negative is yellow.
What is the best wavelength for killing bacteria?
260 nm
Pyramidine dimer
Multiple test technique (sim, etc)
Look over nitrate test
Ok
Virulent E. coli
0157:H7
Coliforms
Ferment lactose
SIM
Contains casein, ferrous salts, agar
Tryptophan–>indole–>Kovacs–>red
Cysteine–>hydrogen sulfide–>ferrous–>black
Motility–>agar
Killers iron agar
Alkaline (red)
Acid (yellow)
Black(h2s)
IMViC
Indole
Methyl red
Voges
Citrate
Red slant/yellow butt
Glucose was utilized only.
Oxidative on top.
Fermentation in bottom.
Yellow slant/yellow butt
Glucose and lactose utilized.
Acids produced–> yellow
Because of fermentation.
