Aerobic Plate Count

Question 1

normal plates’ plate count

Answer 1

25-250 colony per plate

Question 2

how do you record plates that have more than 250 colonies?

Answer 2

TNTC - too numerous to count

Question 3

What are the different types of spreaders?

Answer 3

• chain of colonies not too distinctly separated, appears to be caused by disintegration of bacterial clump.
• develops in film of water between agar and bottom of dish
• develops in film of water at edge or on surface of agar

Question 4

How do you report spreaders?

Answer 4

a. area covered by spreaders + total area of repressed growth exceeds 50% of plate area
b. area of repressed growth exceeds 25% of plate area

Question 5

For the first type of spreaders, if only one chain exists, count it as a

Answer 5

single colony

Question 6

If one or more chains appear to originate from separate sources, count each source as __________

Answer 6

one colony

Question 7

true or false: If one or more chains appear to originate from separate sources, count each source as single colony

Answer 7

false; one colony

Question 8

True or false: Types 2 and 3 usually result in distinct colonies and are counted as such.

Answer 8

true

Question 9

How can you report APC if there’s no colonies counted in a plate?

Answer 9

<1 x lowest dilution used

Question 10

When plate(s) from a sample are known to be contaminated or otherwise unsatisfactory, record result as

Answer 10

laboratory accident

Question 11

when plates from both dilutions yield fewer than 25 CFU each, record APC as

Answer 11

25 x 1/d

Question 12

how many days do you need to incubate yeast and mold?

Answer 12

5

Question 13

If there is no growth at 5 days, re-incubate for

Answer 13

another 48 h

Question 14

In yeast and molds, what is the viable plate count

Answer 14

10-150 colonies