Lab week 6

Question 1

Most known antibiotics stop bacterial growth by disrupting what functions?

Answer 1

1. Cell wall synthesis
2. Membrane permeability
3. Transcription
4. Translation OR
5. Enzyme activity

Question 2

Growth is reversibly inhibited - total count and visible count remain as they were when antibiotic was added to the culture. If the antibiotic is removed, the bacteria will begin to multiply again

Answer 2

Bacteriostatic

Question 3

Bacteria are killed, but the cells remain intact. Total counts will remain when antibiotic was added to the culture, but viable counts will decrease sharply.

Answer 3

Bacteriocidal

Question 4

Bacteria are killed by cell lysis. Total count and viable count decrease sharply after addition of the antibiotic.

Answer 4

Bacteriolytic

Question 5

Method that involves placement of the antibiotic-saturated discs onto an agar plate that has been inoculated completely with a pure culture of one organism.

Answer 5

Kirby-Bauer method

Question 6

If an organism is sensitive to an antibiotic, where will its growth be inhibited on a plate that used the Kirby-Bauer method?

Answer 6

Growth will be inhibited in a circular area called the zone of inhibition

Question 7

If an organism is not sensitive to an antibiotic, what will its growth be like on a plate?

Answer 7

It will grow completely up to and around the edge of the disk, ignoring the antibiotic

Question 8

What type of agar must be used in Kirby-Bauer test?

Answer 8

Mueller-Hinton (MH) agar

Question 9

What depth must plates have when using Kirby-Bauer test?

Answer 9

4mm uniform depth of agar

Question 10

What must the pH be when doing Kirby Bauer test?

Answer 10

between 7.2-7.4

Question 11

What temperature and for how long must plates be incubated when performing Kirby-Bauer test?

Answer 11

37 C for 16-18 hours

Question 12

What antibiotics are we working with in exercise 8?

Answer 12

1. Penicillin G
2. Streptomycin
3. Tetracycline
4. Polymyxin B
5. Rifampin
6. Nitrofurantoin

Question 13

A positive stain that adheres to the flagella, making them more visible under a light microscope

Answer 13

Flagella stain

Question 14

Both positively and negatively stains at the same time: a single dye colors the actual cells, but is repelled from the capsules and stains the background a pink color

Answer 14

capsule stain

Question 15

Primary stain colors the spores green
Secondary stain colors the rest of the cell a pink color
Considered a complex positive stain

Answer 15

Endospore stain

Question 16

Done on organisms with a waxy substance in their cell walls that holds the primary stain (a red dye)
Considered a complex positive stain

Answer 16

acid-fast stain