Medical Microbiology Lab Quiz
An agar that inhibits the growth of certain organisms to allow for growth of other organisms is called...
selective
The only objective lens which can be used with oil is the...
100x
The method used in our lab to achieve isolated colonies is called...
the four quadrant streak
What does the Cafinase Test detect?
Beta-lactamase production
Which test differentiates Staphylococcus from Streptococcus?
Catalase
Test Results for Staphylococcus aureus
Catalase Positive Beta Hemolysis Modified Oxidase Negative Coagulation Positive DNase Positive O/F Fermenter MSA fermenter
Test Results for Staphylococcus epidermidis
Catalase Positive No Hemolysis Modified Oxidase Negative Coagulation Negative DNase Negative O/F Oxidizer MSA Nonfermenter Novobiocin Sensitive
Test Results for Staphylococcus saprophyticus
Catalase Positive No Hemolysis Modified Oxidase Negative Coagulation Negative DNase Negative O/F Oxidizer MSA Fermenter Novobiocin Resistant
Test Results for Micrococcus
Catalase Positive No Hemolysis Modified Oxidase Positive DNase Negative O/F Oxidizer MSA no growth
Micrococcus gram stain result
Gram-positive cocci in clusters
Staphylococcus gram stain result
Gram-positive cocci in clusters
an organism that cannot tolerate high salt conditions will result in __________________ on an MSA plate
NO growth
What is the reagent used in the tube coagulase test?
Rabbit plasma
what is catalase?
an enzyme that decomposes hydrogen peroxide into oxygen and water
a positive modified oxidase test results in...
dark blue/purple color change
True or False: You may eat a snack in lab as long as there are no bacterial cultures on your bench and you have thoroughly washed your hands.
false
a positive tube coagulase test results in..
formation of a clot
Gram Stain Procedure:
1. Primary Stain, crystal violet for 1 min 2. Mordorant, gram's iodine for 1 min 3. Decolorizer, acetone for 5 sec the rinse 4. Counterstain, safranin for 1 min
What is the reagent used in the catalase test?
3% hydrogen peroxide
Which ingredient makes MSA selective?
7.5% sodium chloride
How is the novobiocin test performed?
Making a 0.5 McFarland suspension of the organism in saline and inoculating the suspension to a Mueller Hinton plate with a swab to achieve a confluent lawn of growth (3 way streak)
A rapid biochemical test that can easily separate Micrococcus from Staphylococcus is...
Modified oxidase test
Which Staph species is the cafinase test used on?
Staphylococcus aureus
Which organisms are appropriate for catalase quality control?
Staphylococcus aureus - positive control Streptococcus pyogenes- negative control
a positive DNase test results in...
a clear zone surrounding the growth
an organism that is sensitive to Novobiocin will result in...
a clearing larger than 17mm in diameter
an organism that is resistant to Novobiocin will result in...
a clearing less than 16mm in diameter
an organism that is NOT a mannitol fermenter will result in...
a pink MSA plate
a positive cafinase test will result in...
a red color change
a mannitol fermenter will result in...
a yellow MSA plate
an oxidative O/F test for glucose will result in...
a yellow open tube & a green closed tube
a fermentative O/F test for glucose will result in...
a yellow open tube & a yellow closed tube
In the Lab 2 we will streak both our unknowns onto which media... a) Mannitol salt agar b) Chocolate agar c) TSA d) MacConkey agar
a) Mannitol salt agar
a positive slide coagulase test results in...
agglutination
The laboratory work surface should be wiped with disinfectant (Check all that apply) a) whenever microbes are transferred from one medium to another b) after a spill of microorganisms c) before beginning laboratory procedures d) after completing the lab activities
b, c, d
A positive catalase test results in...
bubbles
What incubation temperature is preferred for the growth of most medically important bacteria? (Check all that apply) a) 45*C b) 25*C c) 37*C d) 98*F
c & d
The coarse and fine focus knobs adjust the distance between... a) the stage and the condenser lens b) the objective and ocular lenses c) the stage and the objective lens d) the ocular lenses
c) the stage and the objective lens
What position should the condenser and diaphragm be in for the best reading of a Gram stain?
condenser raised and diaphragm open
a negative cafinase test will result in...
no color change
