Lab Exam #2 Review #2

Question 1

What is LM differential for?

Answer 1

Bacillus

Question 2

1) What is the indicator in MSA?
2) What color does it turn if the MSA test is positive?
3) Give an example of a positive bacteria on this test

Answer 2

1) Phenol red
2) Turns yellow (acidic) if positive for mannitol fermentation; red is negative
3) S. aureus (SA) +

Question 3

Name 3 tests that differentiate between SA and SE

Answer 3

1) MSA
2) BA
3) SM-110

Question 4

1) What species produce H2S on SS media?
2) What indicator does this test use and what does it indicate?

Answer 4

1) Salmonella and shigella
2) Neutral red turns cultures red if (+) for lactose fermentation

Question 5

1) Besides glucose, fructose, and sucrose fermentation, what else does a TSI test look for?
2) What indicator is used in a TSI test?

Answer 5

1) H2S production
2) Phenol red

Question 6

What are the 3 potential outcomes of an NO3 test?

Answer 6

1) Red color after incubation: nitrate reductase (now NO2-)
2) Red color after zinc: nothing (it’s still NO3)
3) Colorlessness after zinc: denitrification (now N2)

Question 7

Which test is a direct observation of an intracellular enzyme?

Answer 7

ONPG

Question 8

1) What does an SM110 test look for?
2) What species has coagulase and produces orange colonies on this media?

Answer 8

1) Ability to survive on media, gelatinase presence, and glycolysis of fructose-phosphate from mannitol
2) Sa

Question 9

How does an SM-110 test look for gelatinase?

Answer 9

By adding ammonium sulfate and looking for a halo

Question 10

Which media is blue?

Answer 10

MS

Question 11

What color is a SIM test when positive for indole? What is added to do this?

Answer 11

Kovac’s solution is added, turns red/purple if positive
(stays yellow if negative)

Question 12

1) What indicator does a urea test use?
2) What color is it when positive in this test?

Answer 12

1) Phenol red
2) Pink/purple when (+), yellow when negative

Question 13

How can you tell if a nutrient gelatin test is positive or negative?

Answer 13

Stays liquid = positive
Turns solid in fridge = negative

Question 14

What color is a nutrient starch test when positive? Why?

Answer 14

Grams iodine sticks to starch and turns it purple, so clearing is a positive (+) result for amylase

Question 15

1) What is phenylalanine degraded into in the PHE test? What does this bind with?
2) What color is a PHE test when positive?

Answer 15

1) PPA; binds with FeCl3
2) Green = (+)

Question 16

What is another name for a catalase test?

Answer 16

TSA

Question 17

What is another name for a coagulase test?

Answer 17

TSB

Question 18

1) What is TSB (coagulase) selective for?
2) What is TSB differential for?

Answer 18

1) G+ cocci
2) SA+; SE-

Question 19

1) What is in SM-110 media that makes it selective?
2) Where does the fructose-phosphate sometimes used in glycolysis come from?

Answer 19

1) Selective for G+ because G- can’t survive on high NaCl media
2) The mannitol

Question 20

Name 2 colors of colonies found on MS

Answer 20

1) Salivaris: gum drop colonies
2) Mitis & E. faecilis: small dark blue colonies

Question 21

What is MS media selective for?differential for?

Answer 21

Selective for G+; differential for strep

Question 22

What type of bacteria make H2S and are motile in a SIM test?

Answer 22

Some G- rods