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MICROBIO LEC > Physical Means of Controlling Microbial Growth > Flashcards

Physical Means of Controlling Microbial Growth Flashcards

1
Q
  • Removes particles less than 3um and greater than 10um in size with 99.9% efficiency, but does not ensure sterilization
  • Used in clean rooms: quarantine, biological safety labs
A

High-efficiency particulate air (HEPA) filter (disinfection)

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2
Q

Practice of using chemical agents used on body surfaces to safely reduce microbial numbers

A

Antisepsis

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3
Q

Methods of heat sterilization

A
  • Dry heat
  • Moist heat
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4
Q

Thermal death time determines

A

Heat sensitivity of microorganism

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5
Q

Food-related factors that may affect heat sensitivity of endospores

A
  • Low acidic pH kills microorganisms faster
  • High sugar, protein, or fat content decreases heat penetration
  • Effect of salt conc. is species specific
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6
Q

Endospores must be exposed for a (blank) period of time and (blank) temp. when using dry heat

A

longer, higher

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7
Q

True or false. UV light is limited to disinfecting exposed surfaces only.

A

True.

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8
Q

Which kills in autoclaving, temperature or pressure?

A

Temperature

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9
Q

True or false. Sanitization is less effective than disinfection. Because of this, it is not safe for food contact surfaces.

A

False. It is safe and does not involve toxic levels of anti-microbial agents.

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10
Q
  • X-rays and gamma rays
  • Produces high reactive molecules that can destroy DNA, lipids, and proteins
A

Ionizing radiation (sterilization)

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11
Q

Most accessible and widespread method of controlling microbial growth

A

Heat sterilization

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12
Q
  • Prevents spoilage and preserves food by decreasing microbial growth rate
  • Does not kill microorganism
A

Refrigeration and freezing

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13
Q

Factors that affect efficacy of disinfection

A
  • Nature and no. of cells
  • Type and conc. of disinfectant
  • Type and condition of surface to be disinfected
  • Duration of exposure
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14
Q

Serves to reduce the no. of microorganisms to a safe hygienic level

A

Sanitization

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15
Q
  • Subjects milk in 74°C -> 140°C -> 74°C in less than 5 mins.
  • Allows milk to be stored in room temp. for 1-3 months
A

Ultra-high temperature (UHT) (sterilization)

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16
Q

Simplest method of decontamination, temperature at 100°C kills most pathogenic organisms

A

Boiling (disinfection)

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17
Q
  • Non-ionizing radiation
  • Uses wavelengths that cause mutations in microbial DNA that result to death
  • May be ineffective bc of light activated repair mechanisms
A

UV Radiation

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18
Q

Use of conduction, usually at 170°C for 1 hr, 160°C for 2hrs

A

Hot air convection oven (sterilization)

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19
Q
  • Made of high tensile-strength polymers with numerous microscopic pores
  • Used with a syringe and sterile collecting vessel; acts like a sieve to trap particles
A

Liquid filtration via membrane filters (sterilization)

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20
Q

Completely eliminates all viable microorganisms, including endospores

A

Sterilization

21
Q

Use of open flame

A

Flame-sterilization (sterilization)

22
Q

True or false. Relationship of (D) with time is exponential.

A

True.

23
Q
  • Used for milk and heat-sensitive liquids
  • Does not kill all, only reduces microbial load
  • Increases shelf life of perishable liquids
A

Pasteurization (disinfection)

24
Q
  • Water from frozen materials are drawn out in a vacuum
  • High-quality products viable for years
A

Freeze-drying (lyophilization)

25
Q

Eliminates nearly all recognized pathogens but not necessarily all microbial forms (eg. endospores)

A

Disinfection

26
Q

Practice of rendering an area or objects safe to handle by inactivating or reducing contaminants to an acceptable level

A

Decontamination (Decon, Decontam)

27
Q

Uses combustion to destroy organic matter; waste disposal

A

Incineration (sterilization)

28
Q

Amount of time it takes to reduce a bacterial population 1-fold

A

Decimal reduction time (D)

29
Q

Pathogenic bacteria that pasteurization can kill

A
  • E. coli O157:H7 (causes hemorrhagic diarrhea)
  • Listeria monocytogenes
  • Campylobacter spp.
30
Q

Absence of water inhibits enzymatic activities

A

Dying (Desiccation) [Eg. yeast, dried fruit, etc.]

31
Q

True or false. Endospores do not survive after boiling.

A

False. They do.

32
Q
  • Controlled milk flow rate through a tube
  • Heats milk at 71°C for 15s then cooled
A

Flash pasteurization (disinfection)

33
Q

Fibrous sheet made of overlapping paper or glass fibers that trap particles

A

Air filtration via depth filters

34
Q

Lethal dose of Gy for humans

A

10Gy

35
Q

Factors that need to be considered when using heat sterilization

A
  • Nature of the microorganism
  • Sensitivity to heat
  • Duration of the heat treatment
36
Q

Time it takes to kill all cells with a gvien temp.

A

Thermal death time

37
Q

Probability of a microorganism surviving in sterilization

A

One in a million

38
Q

Absorbed radiation dose per gram of tissue

A

Grays (Gy)

39
Q

Uses steam coupled with pressure to kill microorganisms including endospores

A

Autoclaving (sterilization)

40
Q

Conditions of autoclaving

A

121°C, 15 psi, 15-20 mins.

41
Q
  • Non-ionizing radiation
  • Uses wavelengths that cause mutations in microbial DNA that result to death
  • May be ineffective bc of light activated repair mechanisms
A

UV Radiation

42
Q

Examples of antiseptics

A

Iodine in betadine, antibacterial soap, hydrogen peroxide, alcohol

43
Q

(D) is dependent on the following:

A
  • Duration
  • Temperature
44
Q

Slow heating and penetrating, sterilize objects and glassware (eg. flame-sterilization, hot air, convection ovens, incineration)

A

Dry heat

45
Q

Thin polycarbonate film that is irradiated and chemically etched to yield uniform holes

A

Nucleopore filter

46
Q

Decimal reduction time of endospores

A

121°C for 4-5 mins

47
Q

Decimal reduction time of vegetative cells

A

65°C for 0.1-0.5 mins.

48
Q

Faster heating and steam penetration, less (D) values - kills microorganisms faster (eg. boiling, autoclaving, pasteurization)

A

Moist heat

MICROBIO LEC (6 decks)

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