Lab 3

Question 1

What temperature kills most bacteria?

Answer 1

70 degrees for 1-5 minutes

Question 2

What are thermoduric bacteria?

Answer 2

Bacteria that survive pasteurisation temps, 72 degrees for 15secs

Question 3

At what wave length is UV light bactericidal?

Answer 3

250 - 260nm

Question 4

What does a low pressure mercury vapour lamp do?

Answer 4

Emits a very high percentage of UV light at a wave length of 254nm

Question 5

What is a bacterial lawn?

Answer 5

A continuous cover of bacteria on the surface of a growth medium, used to test effectiveness of antibiotics

Question 6

What are the applications of UV sterilisation?

Answer 6

• purification of water
• sterilisation of vaccines
• reduction of viable microbes in premises/rooms

Question 7

What is the zone of inhibition?

Answer 7

A circular area around the spot of an antibiotic or antiseptic/disinfectant in which the bacteria colonies do not grow, used to measure the susceptibility of the bacteria to the antibiotic, antiseptic etc

Question 8

What is a mastring?

Answer 8

An antibiotic susceptibility ring device for simultaneous testing of the equivalent of 6 or 8 antibiotic discs

Question 9

What will affect the size of the zone of inhibition? (5 points)

Answer 9

• the amount of bacteria on the plate
• the type of bacteria
• the concentration of antibiotic
• the ease with which the antibiotic diffuses into the agar
• the size of the disc used

Question 10

What does the zone of inhibition indicate?

Answer 10

Which antibiotic would be the most effective in killing an organism