October 30

Question 1

Thermal Death Point

Answer 1

Lowest temperature which will kill a population of microbes in 10 minutes

Question 2

Thermal Death Time

Answer 2

Time required at a specific temperature to kill a population of microbes

Question 3

Muller-Hinton Agar

Answer 3

Not selective

Supports growth of many bacteria

Loose agar allows for easy diffusion of chemical through agar

Question 4

Disk Diffusion Method

Answer 4

Uses MHA

Heavily innoculate plate with microbe

Allow plate to rest for several minutes

Sterile paper disks soaked in chemical to test

Inncubate after placing on surface of agar

Measure zone of inhibition around each disk

Question 5

Kirby Baur Assay

Answer 5

Diffusion (disk) for antibiotics, use with disks preloaded with exact amount of antibiotics, check zone of inhibition

1. Resistant
2. Intermediate
3. Sensative

Question 6

MIC

Answer 6

Minimum inhibitory concentration

Widely used

Uses MH broth

Use different test tubes with different concentrations of the chemical

Inoculate

Look for first tube with no growth, this is the MIC

Question 7

Methods of Microbial Control

Answer 7

1. heat
2. Low temperatures
3. UV
4. Chemical

Question 8

Microbial Control using High Temperatures

Answer 8

Causes proteins to denature

Leaky cell membrane

Affects transport

Two ways: moist head or dry heat

Question 9

Moist Heat (Microbial control method)

Answer 9

More effective than dry heat

Boiling may not kill cysts or endospores

Two ways:

1. Autoclave: pressure applied to boiling water, 121°C at 15psi for 15 minutes
2. Pasturization: kills potential pathogens in food

Question 10

Pasturization Methods

Answer 10

Batch method: 30 minutes at 60°C

Ultra-high temp pasturization: effects the taste of food 134° for 1 second

Ultra-high temp sterilization: 140°C for 1 second, allows foods to be stored at room temperature

Question 11

Dry Heat

Answer 11

Causes denaturation

Oxidation

121°C for 16 hours

Ex. Incineration approx. 1600°C

Question 12

Low Temperature Microbial Control

Answer 12

Membrane gelling affects transport, reactions slow, makes liquid water unavailable

Freezing: below 0°C

Refrigeration: 0°C-7°C halts growth, growth continues when temperatures rise

Question 13

UV Radiation

Answer 13

Induces thymine dimers

Prevents replication from occurring properly

Good for surfaces

Question 14

Phenols

Answer 14

Intermediate to low level

Denatures proteins

Disrupts cell membranes

Common in health care settings, labs, and homes

Effective in the presense of organic matter

Stable (active for a long time)

Ex. Lysol

Question 15

Alcohol

Answer 15

Intermediate disinfectant and antiseptic

Denatures proteins

Disrupts cell membranes

Evaporates quickly (good or bad)

Question 16

Tincture