Microbial Growth Control

Question 1

TERMINOLOGIES (Physical)

1. kills all forms of microbial life including bacterial spores
2. destroys pathogenic microorganisms but not endospores & prion
3. dispose of reducing the microorganism count
4. lowest temp at which all microbes in liquid culture will be killed in 10mins
5. length of time required to kill all bacteria in liquid culture at a given temp
6. length of time in which 90% of bacterial population will be killed

Answer 1

1. Sterilization
2. Disinfection
3. Decontamination
4. Thermal Death Point
5. Thermal Death Time
6. Decimal Reduction Time

Question 2

1. Principle of Moist Heat (3)
2. Principle of Dry Heat

Answer 2

Principle of Moist Heat
- coagulation of enzymes
- coagulation of structural proteins
- degradation of nucleic acids

Principle of Dry Heat
- denaturation of proteins

Question 3

MOIST HEAT

coagulation accompanied by ______

1. kills vegetative bacteria but not spores and viruses
   - temp
2. fastest & simplest method of sterilization
   - temp for sterilization
   - temp for decontamination
   - kills endospores & prions (w/ higher temp & contact time = _____ or _____)
   - principle
   - biological indicator

Answer 3

hydrolysis

1. Boiling
   - 100C for 10-15mins
2. Autoclave
   - 121C at 15psi for 15-30mins
   - 132C at 15psi for 30-60mins
   - 100C for 4.5-5hrs; 134C for 30mins
   - steak under pressure
   - Bacillus stearothermophilus

Question 4

Moist HET

1. kills vegetative cells & endospores
   - temp
2. for protein rich media like Lowenstein-Jensen Medium (egg-based)
   - temp
   - w/ ___ it hardens
   - w/ ____ it evaporates
3. ; prevents
   food-borne illnesses & spoilag
   - low temp
   - high temp
   - ultra high

Answer 4

1. Intermittent Sterilization
   - steam for 1000C for 30mins for 3 consecutive days
2. Inspissation
   - 75-80Cfor 2hrs for 3 consecutive days
   - autoclave
   - inspissation
3. Pasteurization
   - 65C for 30mins
   - 72C for 15s
   - 140C for 3s

Question 5

Dry Heat
Kills by _____
1. burns organisms & physically destroys bacteri
2. for metals, glasswares, some powders, oils and wax
- temp
- indicator
3. infective materials in sample are gone in waste
- temp
4. control the spread of communicable diseases
5. earliest method of sterilization
- Neisseria gonorrhea
- Bacillus & Clostridium
- Mycobacterium tuberculosis

Answer 5

Oxidation

1. Direct Heating
2. Oven-Heating
   - 160-170C for 1.5-2hrs
   - Bacillus subtilis variant piger
3. Incineration
   - 870-980C
4. Cremation
5. Desiccation
   - 1hr
   - 10yrs
   - several months

Question 6

Filtration
1. membrane filters composed of
- range for bacteria
2. Air filtration uses
- remove bacteria as large as

Answer 6

1. nitrocellulose/ cellulose ester
   - 0.22-0.45um
2. High Efficiency Particulate Air (HEPA)
   - 0.3um

Question 7

Ionizing
1. w/ higher energy & higher penetrating power than UV
- produces
2. its high energy breaks chemical bonds that are vital in cell growth

Non ionizing
1. causes damage to cellular DNA by producing

Answer 7

Ionizing
1. X ray
- hydroxyl radicals
2. Gamma rays

Non ionizing
1. thymine dimer

Question 8

Mechanical Methods
1. Sound waves for delicate
2. Grinding
3. Shaking

Answer 8

1. Sonic vibration
2. Trituration
3. shaking

Question 9

Cold Freezing & Refrigeration

1. ref temp
2. freezing temp
   - does not kill most microbes
   - more harmful as ice crystals disrupt cell structure

_____: low temperature dehydration

Answer 9

1. 0-7
   2.
   - flash freezing
   - slow freezing

Lyophilization