Lab 001 Flashcards
This test differentiates catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species
Catalase test
During catalase test, aerobic and anaerobic organisms produce two toxins during normal metabolism, these are
Hydrogen peroxide
Superoxide radical
Enzyme that can convert hydrogen peroxide to water and oxygen
Catalase
In catalase test, what percent of hydrogen peroxide will you add onto the medium?
30%
Positive and negative catalase
Pos: Staphylococcus aureus
Neg: Streptococcus pyogenes
The test used to differentiate Staphylococcus aureus and coagulase negative staphylococci
Coagulase test
S. aureus produce two forms of coagulase, these are
Bound and free
Coagulase also known as clumping factor
Bound coagulase
It is bound to the bacterial cell wall and reacts directly with fibrinogen. This results in the precipitation of fibrinogen on the staphylococcal cells to clump when a bacterial suspenses is mixed with plasma
Bound coagulase
An extracellular protein enzyme that causes the formation of a clot when S. aureus colonies are incubated with plasma
Free coagulase
The clotting mechanism in coagulase test involves activation of a _________, which is a modified or derived thrombin molecule, to form a coagulase-CRF complex
Coagulase-reacting factor (CRF)
Pos and neg of coagulase test
Pos: Staphylococcus aureus
Neg: Staphylococcus epidermidis
These tests are routine being done in the laboratory for presumptive identification of microorganisms mostly belong to family Enterobacteriaceae and other related species
IMViC tests
One of the degradation products from the metabolism of amino acid tryptophan
Indole
In indole production, the the tryptophan test medium is observed by the development of a red color after adding the solution contain
p-dimethylaminobenzaldehyde
Procedure of Indole test
- Inoculate SIM by stabbing it halfway through the medium
- Incubate at 35-37C for 18-24 hrs
- Add 6 drops of Kovac’s or Ehrlich’s rgnt
Expected results in indole test
Pink to wine colored ring
Positive and negative organism of indole test
Pos: E. Coli
Neg: Klebsiella pneumoniae
Indicator for methyl red test
Methyl red
Bacteria that follow primarily the mixed acid fermentation route often produce sufficient acid to maintain a pH
Below 4.4
Test that provides valuable characteristic in identifying bacterial ability to produce strong acids from glucose
Methyl red test
Procedure of methyl red test
- Inoculate bacteria in an MRVP broth for 48-72 hrs in ambient temperature
- Add 5 drops of Methyl Red rgnt directly to the broth
Expected results of the methyl red test
Positive: bright red color
Weakly positive: red-orange color
Negative: yellow color
The test used to detect the formulation of acethyl methyl carbinol (acetoin) as a product of glucose formation
Voges-Proskauer Test
It is formed as a product of an alternative pathway of glucose fermentation utilized by some species of Enterobacteriaceae
Acetoin
Procedure of Voges-Proskauer test
- Inoculate bacteria in an MRVP broth for 48-72 hrs in ambient temp
- Add 6-8 drops of 5% alpha napthol, and 4 drops of 40% potassium hydroxide
- Shake gently and leave undisturbed for 10-15 mins
Pos and neg bacterias of Voges-Proskauer test
Methyl red - VP
MR (+)/VP(-): E. Coli
MR (-)/VP (+): Enteribacter aerogenes
Expected results of the VP test
Pos: red color
Neg: yellow color
This is to determine if bacterium can utilize citrate as sole source of carbon for metabolism and growth
Citrate Utilization Test
Expected result of citrate utilization test
Pos: green to blue
Neg: green
Pos and neg bacteria in the citrate utilization test
Pos: Enterobacter aerogenes
Neg: E. Coli
LIA is useful for identification of
Salmonella, Proteus, Providencia, and Morganella
They are members of Proteus group that are the only members of the Enterobacteriaceae that are deaminase positive
Proteus, Providencia, and Morganella
If the organism produces lysine dearboxylase, ____ is formed
Cadaverine
Neutralizes the organic acids formed by glucose fermentation, and the butt of the medium reverts to the alkaline state (purple)
Cadaverine
In LIA, if oxidative deamination occurs, a compound formed, in the presence of ______ and a coenzyme, _______, forms a burgundy color on the slant
Ferric ammonium citrate
Flavin mononucleotide
pH indicator of LIA
Bromocresol purple
Procedure of LIA
- Deep/butt is stab twice
- Incubate at 35-37c for 24 hrs
LIA expected results:
Lysine decarboxylation and no fermentation of glucose
K/K (purple/purple)
LIA expected results:
Glucose fermentation
K/A (purple/yellow)
LIA expected results:
Lysine deamination and glucose fermentation
Red slant/acid butt (R/A)
