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Microbiology > Chapter 5 - Control of Microbial Growth > Flashcards

Chapter 5 - Control of Microbial Growth Flashcards

(40 cards)

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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?

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

What does boiling do?

Study These Flashcards
A

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

19
Q

What does pasteurization do?

Study These Flashcards
A

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

20
Q

What does autoclaving do?

Study These Flashcards
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?

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

What does incineration do?

Study These Flashcards
A

burns cell components to ash

  • flaming loop
  • STERILIZES
23
Q

What do dry heat ovens do?

Study These Flashcards
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?

Study These Flashcards
A

Fluids- various pore sizes remove bacteria

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

25
What are the two types of radiation?
1. Ionizing | 2. UV radiation
26
What does ionizing radiation do?
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
What does UV radiation do?
Damages DNA - penetrates poorly - -used for air and drinking water; surfaces - DOES NOT STERILIZE - microwaves kill by heating but not directly, unevenly
28
What does high pressure do?
Treatments of 130,000 psi denature proteins and alter permeability of cell - products retain color and flavor - DOES NOT STERILIZE
29
What are alcohols and what are they used for?
- 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
What are aldehydes and what are they used for?
- 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
What are Biguanides and what are they used for?
- Chlorhexidine most effective - used as antiseptics - stays on skin, mucous membranes - common in skin cream, mouthwash
32
What is Ethylene oxide gas used for?
- 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
What are metal compounds and what are they used for?
- 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
What are halogens and what are they used for?
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
What are peroxygens and what are they used for?
- 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
What are Phenolic compounds (phenolics) and what are they used for?
- 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
What are Quaternary Ammonium Compounds and what are they used for? (Quats)
- cationic (+ charged) detergents | - nontoxic, used to disinfect food preparation surfaces
38
What are Chemical preservatives?
- 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
What does low temperature storage do?
- 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
What does reducing available water do?
- 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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