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Microbiology > Chapter 5 Control of Microbial Growth > Flashcards

Chapter 5 Control of Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

Sterilization

A

Absolute removal or destruction of ALL microorganisms and viruses

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2
Q

Disinfection

A
  • Destruction of most microbes including pathogens
  • Does not kill all microbes
  • Ex. Chemical disinfectants
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3
Q

Antisepsis (Antiseptic)

A
  • Disinfection of skin or living tissue

- Normally using less harsh treatments (chemicals)

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4
Q

Degerming

A
  • Removal of MOST microbes from a limited area

- Ex. Washing hands with soap and water

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5
Q

Sanitization

A

Lowering microbial counts to a safe level to meet public health standards

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6
Q

-cidal vs. -static

A

-An agent that kills microbes has the suffix -cide
- An agent that stops the growth of microbes -static or -stasis
Example:
1) A bacteriocidal kills bacteria
2) A bacteriostatic agent stops bacteria from reproducing

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7
Q

Asepsis (aseptic)

A
  • An area is free of significant contamination

- Modern surgical techniques are aseptic to minimize infection

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8
Q

Using Heat to Destroy Microbes

A
  • Kills microbes by destroying enzymes - bactericidal (germicidal)
  • Can be used several ways:
    1) Boiling for 5 minutes
    2) Pasteurization
    3) UHT
    4) Autoclave
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9
Q

Boiling for 5 minutes

A
  • Kills most pathogenic bacteria- but not all endospores
  • Most Viruses
  • This is disinfection, not sterilization!
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10
Q

Pasteurization

A
  • Sufficient to eliminate pathogens and to lower microbial numbers to slow spoilage
  • Classic treatment = mild heating to 63 degree C for 30 minutes
  • HTST (High Temperature Short Time) = 72 degree C for 15 seconds
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11
Q

UHT (Ultra High Temperature)

A
  • =140 degree C for 3 seconds

- Destroys all microorganisms that can grow under normal storage conditions

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12
Q

Autoclave

A
  • Employs pressure (15 psi) and steam (121 C)
  • Kills all endospores in about 15 mins
  • Best method for sterilization
  • Used for:
    1) Culture Media 2) Hospital instruments 3) Hospital materials that can withstand heat and moisture
    4) Requires that all solid surfaces are exposed to steam
    5) All liquids must reach a temperature of 121 C
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13
Q

Dry Heat Sterilization (methods)

A
  • Direct Flaming
  • Incineration
  • Hot air sterilization
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14
Q

Direct Flaming

A
  • Dry heat sterilization
  • Used in microbiology laboratory to sterilize inoculation needles and loops
  • Metallic instruments must be red-hot
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15
Q

Incineration

A

Effective way to dispose of contaminated materials

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16
Q

Hot Air Sterilization

A
  • Drying oven
  • Materials should stay at 170C for 2 hours
  • Used for dry materials that are not temperature sensitive
  • Examples: Glassware, some dry chemicals
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17
Q

Filtration

A

-Vacuum used to force liquid through filter with very small pores - 0.1um, 0.22um or 0.45um
-Pores are too small for bacteria to pass
-Used to sterilize temperature sensitive liquids:
Antibiotics
Enzymes
Some vaccines

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18
Q

Air Filtration

A
  • High-efficiency particulate air (HEPA) filters

- Used in some operating room to remove all microbes larger than 0.3um

19
Q

Refrigeration and Freezing (Low Temperatures)

A

Refrigeration

  • Slows or stops microbial growth
  • Bacteriostatic (or germistatic)

Freezing

  • Stops microbial growth
  • Only a small portion of microbes will die
  • Bacteriostatic
20
Q

High Pressure

A
  • Liquid suspensions treated with high pressure
  • May kill many bacterial cells- bacteriocidal
  • Does not kill endospores
  • Not sterilization
21
Q

Dessication

A
  • Removal of water (drying)

- slows or stops growth - but usually does not kill microbes - bacteriostatic

22
Q

Osmotic Pressure

A
  • High concentrations of salts and sugars - hypertonic environment
  • Can kill some bacteria - bacteriocidal or bacteriostatic
  • Molds and yeasts are more resistant
23
Q

Radiation

A

-Destroys DNA
-X-rays and Gamma rays penetrate materials
UV and high energy electron beams - used on surfaces

24
Q

Microwaves

A
  • Do not kill microorganisms directly
  • They heat water
  • High temperatures can be used to disinfect materials
25
Q

Chemical used to Destroy Microbes

A

-Most can only be used for disinfection - not sterilization

26
Q

Disk Diffusion Method

A
  • Disk of filter paper soaked in chemical disinfectant
  • Placed on ager plate that has already been inoculated with bacteria
  • The plate is incubated until bacteria grow
  • Zone of clearing determines effectiveness
27
Q

Phenolic Compound (Phenols)

A
  • Disrupt plasma membranes, denature proteins - Bacteriocidal
  • Very effective, remain active long after application
  • Suitable for disinfection of soiled surfaces
  • Often mixed with other compounds to reduce toxicity
28
Q

Hexachlorophene (Phenols)

A
  • Useful against bacteria that cause skin infections in newborns
  • Can be used to disinfect surfaces in nurseries
  • Caution must be used - causes neurological disorders
29
Q

Triclosan (Phenosl)

A

Used in some personal hygiene products - cosmetics and deodorant soaps

30
Q

Biguanides

A

1) Chlorhexidine - attacks membrane (bacteriocidal)
- To control microbes on skin and mucous membranes
2) Used in surgical hand scrubs
- Can persist for up to 6 hours
- Only kills some viruses, does not destroy endospores

31
Q

Halogens

A
  • Destroys proteins and membranes
  • Used as disinfectants and antiseptics:
    1) Chlorine
    2) Iodine
32
Q

Chlorine

A
  • Forms hypochlorous acid in water - strong oxidizing agent - denatures enzymes
  • Examples:
    1) Household bleach (sodium hypochlorite) –> excellent disinfectant
    2) Chlorine dioxide - sterilizing gas
33
Q

Iodine

A
  • Frequently used as an antiseptic
  • Examples:
    1) Tincture of iodine - in an alcohol solution
    2) Iodophore - linked to carrier molecules so that is released slowly over time (Betadine)
34
Q

Alcohols

A
  • Denature proteins and disrupt membranes
  • Kills bacteria and fungi
  • Does not kill endospores and some viruses
  • Often used to disinfect surfaces in a lab, or to degree skin
  • Does not suffice as an antiseptic (combined with other chemicals to enhance)
35
Q

Ethanol (Type of Alcohol)

A

70% most effective

36
Q

Isopropanol

A

Rubbing alcohol

37
Q

Silver Nitrate (Heavy Metal)

A
  • 1%

- Used as eye drops for new-born infants, to protect against gonorrhoeal ophthalmia

38
Q

Silver Sulfadiazine

A

Topical cream for burns

39
Q

Silver ions

A

are incorporated into bandages and catheters to slow growth of microbes

40
Q

Copper Sulfate

A

Used to inhibit algae in reservoirs

41
Q

Mercuric Chloride

A

Used in paint to control mildew (toxic!)

42
Q

Zinc Chloride

A

Used as antiseptic mouthwashes

43
Q

Gases Chemosterilizers

A
  • Chemical gasses used for sterilization
  • Ethylene Oxide
    1) Denatures proteins - germicidal
    2) Kills all microbes - including endospores and viruses
    3) Requires 4 -18 hours of exposure
    4) Highly penetrating - passes through plastics
    5) Used to sterilize disposable hospital equipment and lab supplies
44
Q

Oxidizing Agents

A
  • Oxidize and denature proteins
  • Useful against anaerobic organisms
    1) Hydrogen peroxide - common antiseptic for wounds
    2) Ozone - used with chlorine to disinfect water
    3) Benzoyl peroxide - used as antiseptic on skin (Kills bacteria that causes acne)

Microbiology (17 decks)

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