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Microbiology > Chapter 5 - Control of Microbial Growth > Flashcards

Chapter 5 - Control of Microbial Growth Flashcards

1
Q

Who introduced methods to prevent infection of wounds?

A

Lister

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2
Q

What are the 6 approaches to control?

A
  1. Sterilization
  2. Disinfection
  3. Pasteurization
  4. Decontamination
  5. Sanitization
  6. Preservation
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3
Q

What does sterilization do?

A

the sterile item is free of microbes but does not consider prions

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4
Q

What the two categories of Disinfection?

A
  1. disinfectants

2. antiseptics

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5
Q

What is pasteurization?

A

Brief heating to reduce number of spoilage organisms, destroys pathogens (not endospores)
–FOOD

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6
Q

What is preservation?

A

process of delaying spoilage of foods and other perishable products by adjusting the conditions and adding bacteriostatic (growth inhibiting) preservatives

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7
Q

What is special about protozoan cysts and oocysts?

A

They are resistant to disinfectants, excreted in feces, and cause diarrheal disease if ingested

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8
Q

What is special about the Pseudomonas species?

A

it is resistant to and can grow in some disinfectants

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9
Q

What is the D value?

A

The time required to kill 90% of population under specific conditions

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10
Q

What environmental conditions effect antimicrobials?

A
  • Dirt, grease, body fluids can interfere with heat penetration and the action of some chemicals
  • pH, temperature can influence effectiveness
  • -low pH more effective
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11
Q

What are Critical items?

A
  • items that come in direct contact with body tissues
  • -must be sterile
  • -needles and scalpels
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12
Q

What are semicritical instruments?

A
  • items that come in contact with mucous membranes but do not penetrate body tissues
  • -must be free of viruses and vegetative bacteria
  • -includes endoscopes and endotracheal tubes
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13
Q

What are non-critical instruments?

A
  • items that contact unbroken skin only
  • -low risk of transmission
  • -countertops, stethoscopes, blood pressure cuffs
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14
Q

What is innapropriate for use on plastic and other sensitive items?

A
  • heat

- irradiation damages some types of plastic

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15
Q

What cannot be used to treat moisture sensitive material?

A

moist heat

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16
Q

What are the 5 methods of physical microbial control?

A
  1. Moist heat-denatures proteins
  2. Dry heat
  3. Filtration
  4. Radiation
  5. High pressure
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17
Q

What are 3 methods of Moist heat control?

A
  1. Boiling
  2. Pasteurization
  3. Autoclaving (pressurized steam)
18
Q

What does boiling do?

A

boiling for 5 minutes destroys most microorganisms and viruses but not endospores
-DOES NOT STERILIZE

19
Q

What does pasteurization do?

A

decreases the number of heat-sensitive microorganisms including spoilage microbes and pathogens (except sporeformers)
-DOES NOT STERILIZE

20
Q

What does autoclaving do?

A

121˚C at 15psi for 15 minutes destroys endospores

  • STERILIZES
  • canning destroys clostridium botulinum endospores
21
Q

What are 2 methods of Dry heat control?

A
  1. Incineration
  2. Dry heat ovens
    - 200˚C for 90 minutes
22
Q

What does incineration do?

A

burns cell components to ash

  • flaming loop
  • STERILIZES
23
Q

What do dry heat ovens do?

A

destroys cell components and denatures proteins

  • less efficient than moist heat and requires longer times and higher temps
  • oxidizes cell components
24
Q

What are the two forms of filtration and what does each do?

A

Fluids- various pore sizes remove bacteria

Air - HEPA filters remove organisms that have diameter of 0.3um or greater

25
Q

What are the two types of radiation?

A
  1. Ionizing

2. UV radiation

26
Q

What does ionizing radiation do?

A

destroys DNA and possibly damages cytoplasmic membranes

  • produces reactive molecules that damage other cell components and can sterilize items after packaging
  • Gamma and x-ray
  • STERILIZES
27
Q

What does UV radiation do?

A

Damages DNA

  • penetrates poorly
  • -used for air and drinking water; surfaces
  • DOES NOT STERILIZE
  • microwaves kill by heating but not directly, unevenly
28
Q

What does high pressure do?

A

Treatments of 130,000 psi denature proteins and alter permeability of cell

  • products retain color and flavor
  • DOES NOT STERILIZE
29
Q

What are alcohols and what are they used for?

A
  • Ususlly 60%-80% aqueous solutions of ethyl or isopropyl alcohol
  • kill vegetative bacteria and fungi
  • not reliable against endospores and naked viruses
  • used as antiseptic and disinfectant
  • evaporates quickly limiting contact time and pure alcohol not effective
30
Q

What are aldehydes and what are they used for?

A
  • Glutaraldehyde and formaldehyde
  • 2% alkaline glutaraldehyde common sterilant
  • -immersion for 10-12 hrs kills all microbial life
  • Formaldehyde used as a gas or as formalin (37% solution)
  • -effective germicide that kills most microbes quickly
31
Q

What are Biguanides and what are they used for?

A
  • Chlorhexidine most effective
  • used as antiseptics
  • stays on skin, mucous membranes
  • common in skin cream, mouthwash
32
Q

What is Ethylene oxide gas used for?

A
  • Useful gaseous sterilant
  • destroys all microbes including endospores and viruses
  • -STERILIZATION
  • useful in sterilizing heat or moisture-sensitive items
  • sterilizes disposable lab items
  • -petri dishes, pipettes, equipment, implantable devices (pacemakers), artificial hips
33
Q

What are metal compounds and what are they used for?

A
  • high concentrations too toxic to be used medically
  • Silver still used as disinfectant in creams or bandages
  • compounds of mercury, tin, copper, and others once widely used as preservatives
34
Q

What are halogens and what are they used for?

A
  1. Chlorine
    - used as disinfectant but is caustic to skin and mucous membranes
    - 1:100 dilution of household bleach effective
    - presence of organic compounds is a problem
  2. Iodine
    - used as a disinfectant or antiseptic
    - unreliable on endospores
    - commonly used as iodophore
    - -iodine slowly released from carrier molecule
35
Q

What are peroxygens and what are they used for?

A
  • powerful oxidizers used as sterilants
  • Hydrogen peroxide effectiveness depends on surface
    • -less effective as antiseptic; aerobic bacteria produce enzyme catalase
      • –breaks down H2O2 to O2 and H2O
    • -more effective as disinfectant on inanimate objects
    • -vapor phase can be used as sterilant
  • Peracetic acid is more potent than H2O2
    • effective on organic material
    • useful on wide range of material
36
Q

What are Phenolic compounds (phenolics) and what are they used for?

A
  • Phenol, one of the earliest disinfectants
  • wide activity range, reasonable cost, remain effective in presence of detergents and organic matter
  • some sufficiently non-toxic and used in soaps and lotions
  • TRICLOSAN
37
Q

What are Quaternary Ammonium Compounds and what are they used for? (Quats)

A
  • cationic (+ charged) detergents

- nontoxic, used to disinfect food preparation surfaces

38
Q

What are Chemical preservatives?

A
  • weak organic acids (benzoic, sorbic, propionic)
  • control molds and bacteria in foods and cosmetics
  • Nitrate and nitrite used in processed meats
  • -inhibit endospore germination and vegetative cell growth
  • -higher concentrations give meats pink color
39
Q

What does low temperature storage do?

A
  • Refrigeration inhibits (DOESNT KILL) growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions
  • -psychrotrophs and psychrophilic organisms can still grow
  • freezing preserves by stopping all microbial growth
40
Q

What does reducing available water do?

A
  • Inhibits microbes without killing them
  • Accomplished by salting or adding sugar
  • -increases environmental solutes
  • -causes cellular plasmolysis (water exits bacterial cells)
  • Lyophilization (freeze drying) foods is the application of low temperature and drying
  • -used in coffee, milk, meats, fruits, vegetables
  • Drying stops microbial growth but does not reliably kill
  • -numerous cases of salmonellosis from dried eggs

Microbiology (9 decks)

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