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Microbiology > Controlling Microbial Growth > Flashcards

Controlling Microbial Growth Flashcards

1
Q

Antisepsis

A

Reduction in the number of microorganisms and viruses in living tissue

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2
Q

Aseptic

A

Refers to an environment or procedure free of pathogenic contaminents

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3
Q

Cide/Cidal

A

Kills microbes

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4
Q

Degerming

A

Removal of microbes by mechanical means (scrubbing)

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5
Q

Disinfection

A

Destruction of most microorganisms and viruses on nonliving tissue

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6
Q

Pasteurization

A

Use of heat to destroy pathogens and reduce the number of spoilage microorganisms in foods and beverages

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7
Q

Sanitization

A

Removal of pathogens from objects to meet public health standards

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8
Q

Stasis/Static

A

inhibiting growth

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9
Q

Sterilization

A

Destruction of all microorganisms and viruses on or in an object

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10
Q

Microbial Death: Factors affecting how long it takes to kill bacteria:

A
  • Time of exposure
  • environment: slowed by organic matter (feces) and hastened by prior cleaning (heat)
  • number of microbes
  • characteristics: spores, thick lipid coats, protozoan cysts
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11
Q

Actions of microbial control agents:

A
  • mutations- non-functional proteins
  • alterations of membrane permeability- poking holes in membrane causing guts to spill out
  • damage to proteins and nucleic acids- if the proteins are damaged, they may not work. some are more critical than others
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12
Q

Physical control methods:

A
  • Temperature: heat preservation (pasteurization), moist heat, dry heat, low heat.
  • desiccation- drying out
  • osmotic pressure
  • radiation
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13
Q

Heat preservation:

A

must know the temperature and time needed to kill critical bacteria

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14
Q

Thermal Death Time

A

How long it takes to kill a certain bacteria at a certain temperature

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15
Q

Pasteurization

A
  • used when taste is damaged by longer heat (it lowers the numbers of pathogens 63 degrees for 30 minutes)
  • items that are typically pasteurized include milk, juice, ice cream, and yogurt.
  • UHT: sterilization (140 degrees for 1-3 seconds) and can cause product to lose some nutritional value
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16
Q

Moist Heat

A
  • denatures proteins
  • Boiling: 10 minutes for most pathogens, 30 minutes for hepatitis virus, 20 hours for spores
  • Autoclave: uses pressurized steam. 15 psi for 15 minutes at 121 degrees (very penetrating)
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17
Q

Dry Heat

A

Flaming, oven (170 degrees for 2 hours), spores are resistant to dry heat

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18
Q

Low Temp:

A

Refrigerator: Bacteriostatic! most pathogens do not grow. Listeria spp. are psychrotolerant. Refrigeration prevents growth

Freezing: slow freezing causes ice crystals. the ice in the membrane can shatter it. Freezing can kill or preserve pathogens

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19
Q

Membrane filtration

A

Pore size controls which microbes are removed. Using a filter sterilization of 0.2 micrometers will remove all pathogens.

HEPA filters used in safety hoods and operating theaters

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20
Q

Limiting Water

A

Desiccation: Bacteriostatic! One way to desiccate would be Lyophilization which is used to preserve cultures. You do this by removing all H2O molecules and then when you get to the lab, you add water and then it will grow

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21
Q

Osmotic Pressure

A

High concentration of salt or sugar. Molds and yeasts are most resistant

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22
Q

Radiation

A
  • Ionizing radiation: gamma rays, x rays, high energy electron beams- (most energy)
  • ionization of H2O to form OH- radical
  • can cause mutations of DNA and death
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23
Q

Low level and high levels of radiation used for:

A

Low level ionizing radiation used on spices, some meats, and vegetables.
High energy electron beams used for medical supplies

24
Q

UV Radiation (Light)

A
  • Causes Thymine dimers in DNA
  • Germicidal lamps and vaccine disinfection
  • not penetrating
  • can damage eyes
25
Q

Microwaves

A

Has very little effect on some microbes. Microwaves kill vegetative pathogens by heating. Solid Foods heat unevenly

26
Q

Chemical Methods:

A
  • Disinfectants/Antiseptics
  • Surface-Active agents (Surfactants)
  • Chemical food preservatives
  • Aldehydes (Formaldehyde= formalin)
  • Gas sterilization
  • Oxidizing agents
  • [antibiotics]
27
Q

Disinfectants/Antiseptics (Phenols)

A
  • Phenols
  • Stable
  • Persist for long periods after application
  • Active in the presence of organic matter
  • Damage lipid membranes
  • Example: Dettol
28
Q

Phenols:

A

Originally used by Joseph Lister, as carbolic acid vapors during surgery

29
Q

Disinfectants/Antiseptics (Bisphenol)

A
  • Bisphenols
  • Hexachlopophene (pHisoHex) and triclosan
  • antibacterial soap and toothpaste
  • broad spectrum of activity
30
Q

Disinfectants/ Antiseptics (Biguanides)

A
  • Biguanides
  • Chlorhexidine
  • low toxicity
  • used on skin and mucous membranes
  • surgical scrub used in veterinary hospitals (usually pink)
31
Q

Disinfectants/Antiseptics (Halogens)

A
  • Halogens
  • Iodine: used in solution (Betadine and Isodine)
  • Chlorine: gas that forms bleach (hypochlorite) in water. It destroys cell walls and enzymes
32
Q

Disinfectants/ Antiseptics (Alcohol)

A
  • Alcohol
  • Protein denaturation and membrane damage
  • Ethanol and Isopropanol most common
  • Evaporates very quickly (good and bad)
  • 100% alcohol is not good as denaturing proteins requires water molecules
33
Q

Heavy Metals as Disinfectants:

A
  • Denature proteins
  • silver nitrate (topical cream)
  • mercuric chloride (paint) used to be used as an antiseptic. it’s poisonous. was used to treat syphilis
  • copper sulfate (algicide)
  • zinc (mouthwash, paints)
34
Q

Surfactants

A

Decrease surface tension, damages lipid membranes, and it’s in soaps (ivory) and detergents.
- Quaternary ammonium compounds: microbicidal

35
Q

Chemical Food Preservatives

A
    • Sodium benzoate:
  • in acidic foods
  • reduces pH to 5 or lower which inactivates phosphofructokinase
    • Sorbic acid:
  • weak acids
  • inhibits enzymes
    • Calcium propionate
  • used in breads to prevent mold
  • non-toxic but inhibits growth
    • Sodium nitrate/sodium nitrite
  • inhibits Clostridium botulinum
  • toxic
36
Q

Aldehydes

A
  • Formaldehyde (formalin) and glutaraldehyde
  • used to disinfect instruments
  • used to preserve tissues
  • irreversibly cross-links protein molecules
37
Q

Gas Sterilization

A
    • Ethylene oxide
  • denatures proteins
  • kills all spores and microbes with lengthy exposure
  • high penetration
  • for use when sensitive to heat or moisture
38
Q

Oxidizing agents

A
  • benzoyl peroxide
  • hydrogen peroxide
  • ozone
  • peracetic acid (interfere with metabolism, especially obligate anaerobes)
39
Q

What category does ethylene oxide fall under?

A

Gas sterilization

40
Q

What category does phenol fall under?

A

Disinfectant/antiseptic (it is a disinfectant)

41
Q

What category does soaps and detergents fall under?

A

Surfactants

42
Q

What category does halogens fall under?

A

Disinfectant/antiseptic (it is an antiseptic)

43
Q

What category does sodium nitrate and sodium nitrite fall under?

A

Chemical Food Perservative

44
Q

What category does formaldehyde fall under?

A

Aldehyde

45
Q

What category does hydrogen peroxide fall under?

A

Oxidizing agent

46
Q

What category does calcium propionate fall under?

A

Chemical Food Preservation

47
Q

What category does biguanide fall under?

A

Disinfectant/antiseptic

48
Q

What category does benzoyl peroxide fall under?

A

Oxidizing agent

49
Q

What category does sorbic acid fall under?

A

Chemical Food Preservative

50
Q

What category does glutaraldehyde fall under?

A

Aldehyde

51
Q

What category does ozone fall under?

A

Oxidizing agent

52
Q

What category does sodium benzoate fall under?

A

Chemical Food Preservative

53
Q

What category does alcohol fall under?

A

Disinfectant/antiseptic

54
Q

What category does peracetic acid fall under?

A

Oxidizing agent

55
Q

What category does bisphenol fall under?

A

Disinfectant/antiseptic

56
Q

What category does silver nitrate, mercuric chloride, copper sulfate and zinc belong to?

A

Heavy metals as disinfectants

Microbiology (10 decks)

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