Lab 13: Bacterial Death

Question 1

Name the 4 antiseptics/ disinfectants used in the bacterial death exercise

Answer 1

1) Clorox (QAC)
2) Pinesol (DET)
3) Greenworks (CIT)
4) Iodine (IO)

Question 2

What type of disinfectant/ antiseptic is clorox?

Answer 2

A quaternary ammonium compound

Question 3

What type of disinfectant/ antiseptic is pinesol?

Answer 3

A detergent

Question 4

What is greenworks?

Answer 4

Citric acid

Question 5

What two characteristics would you look for in a test regarding the efficacy of chemical agents on bacteria?

Answer 5

1) Quantitative
2) Reproducible

Question 6

What 3 categories of techniques were used to kill bacteria in the bacterial death exercise?

Answer 6

1) Disinfectants/ antiseptics
2) Antibiotics
3) UV radiation

Question 7

What 4 categories antibiotics were used to inhibit bacterial growth in the bacterial death lab? What antibiotic was used to represent each category?

Answer 7

1) Nucleic acid inhibitor: RIF
2) Cell wall inhibitor: AMP
3) Protein synthesis inhibitor: TET
4) Structural analog: SXT

Question 8

1) What type of test was used to measure the efficacy of disinfectants/ antiseptics and antibiotics on bacteria?
2) How is this test interpreted?

Answer 8

1) Disk diffusion test
2) If there is an area of no growth around the disc, the agent was effective

Question 9

How many seconds of UV radiation did each condition get in the bacterial death lab?

Answer 9

0, 10s, 30s, 1m, 2m, 5m, 10m

Question 10

1) What was the first test used to measure the efficacy of chemical agents on bacteria? Why was it not preferable?
2) What test replaced that test?
3) What test replaced the second test?

Answer 10

1) Broth dilution testing; time consuming and resource intensive
2) Disk diffusion testing
3) E-test strips

Question 11

What are the steps of a disk diffusion test?

Answer 11

1) Streak a plate to create a lawn of bacteria
2) Apply antibiotic or disinfectant disk
3) Incubate
4) Zone of inhibition is created around the disk if agent is effective (i.e. no bacteria around disk)

Question 12

Why is there a gradient observed around the disk in the disk diffusion test?

Answer 12

Because the agent diffuses from the disk into the agar medium

Question 13

Why did the BS 5-day old culture grow better than the newer culture under UV conditions?

Answer 13

Because the bacteria had sporulated