Micro Lab Practical 3
Card Set Information
Micro Lab Practical 3
PEA - Selective, Differential or Both?
Inhibiting agent in PEA & what it inhibits.
Phenyl Ethyl Alcohol;
Name 2 species that grow on PEA.
What microbes grow best on PEA Agar?
What kind of test is 6.5% Salt Broth?
What does a Salt Broth test separate?
E. fecalis & S. bovis
HE Agar - Selective, Differential, or Both?
What makes HE Agar selective? Differential?
Selective = bile salts inhibit gram (-)
Differential = iron turns black
What are the sugars in HE Agar?
lactose, sucrose, salacin
What does HEA stand for?
Hektoen Enteric Agar
Name 2 pathogens in which HEA is used to isolate and ID.
Salmonella (produces H2S)
Shigella (does not produce H2S)
If the TSI test shows a black butt, what does that mean and what test should you do next?
It means it's Salmonella or Proteus. Do a urease test.
What microbe is alpha hemolytic?
Is an alpha hemolytic microbe bacitracin resistant or sensitive?
In a Hemolysis test, what does a complete zone of clearing indicate?
Beta hemolysis (complete hemolysis)
What microbes are beta hemolytic?
Group A Strep (S. pyogenes)
Are beta hemolytic microbes sensitive or resistant to bacitracin?
The oxidase test detects the presence of what enzyme?
Name one gram (-) diplococcus pathogen that is positive for cytochrome oxidase.
What diseases does Neisseria cause?
What is the Kirby Bauer test used to determine?
Sensitivity and resistance to antibiotics
What does a large ZOC in a Kirby Bauer test indicate?
sensitivity to antibiotics
What kind of test is a Bile Esculin test?
gram (+) strep test
Is Bile Esculin Selective, Differential, or Both?
Esculin is a substance that is converted to what?
glucose & esculetin
What makes the Bile Esculin test selective?
bile salts inhibit gram (+) EXCEPT Group D Strep
What is the substrate in Bile Esculin Media?
Esculin - can be digested to esculetin; in presence of iron will change color (black)
Describe a positive Bile Esculin test.
What is added to Bile Esculin media to give it a positive reaction?
What group are positive for growth and esculin digestion?
Group D Strep
Name two species of gram (+) cocci in which Bile Esculin media is used to differentiate.
E. fecalis; S. bovis
What specific organism produces dark, blue-black colonies with a metallic green sheen on EMB agar?
Is E. coli coliform or non-coliform?
EMB is frequently used in water testing labs to detect what?
What is the substrate and what are the end products in a catalase test?
substrate = H2O2
end products = H2O & O2
Which gram (+) cocci produces a (+) result for the catalase test? Which produces a (-) result?
Staph = POS
Strep = NEG
What does the catalase test separate?
Staph & Strep
MAC - Selective, Differential or Both?
What are the inhibiting agents in MAC?
Bile salts & crystal violet
What is the MAC media selective for?
If you get pink colonies on a MAC plate, what does that indicate?
What group of microbes does the MAC media inhibit?
What color is a positive fermentation on a MAC plate? What does it mean?
pink; ferments lactose and is an acid
What microbes will grow on a MAC plate?
Why did we use Serratia marcesens in the UV light experiment?
It grows fast and is red
What is the target of the UV light in killing microbes?
What does the UV light experiment cause to form?
Describe light repair.
An enzyme system that can repair minor DNA damage;
light repair photo reactivating enzyme absorbs light & clears the thymine dimer to reform twoadjacent thymine residue
Coagulase is the enzyme that causes _______ to be converted to ________.
Describe a positive coagulase test.
solid; clump; clot
Which pathogen will produce a positive coagulase test?
What do we use instead of coagulase on our flow chart?
What does MSA stand for?
Manitol Salt Agar
What specific group of microbes do we use MSA to ID?
What is the indicator in MSA?
Name the potential pathogen that grows on MSA & is (+) for MSA.
Is MSA Selective, Differential, or Both?
What makes MSA Selective?
salt makes it selective for Staph
Why is MSA hypertonic?
7% salt which is greater than 1% isotonic
Is Blood Agar Selective, Differential, or Both? Why?
because of hemolysis
What is added to blood agar to give it the red color?
5% sheep blood
What is the "A" disk?
What is the "O" disk?
Name one specific pathogen that gives a ZOC with an A disk on blood agar.
The ZOC around an A disk on blood agar indicates what?
sensitivity to bacitracin
What is the ZOC around the individual colonies on a blood agar plate?