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Microbial Control > Lecture 19 > Flashcards

Lecture 19 Flashcards

1
Q

Importance of Microbial control!

A
  • To prevent the spread of infectious diseases
  • To prevent food spoilage
  • To prevent disruptions or interference in an industrial process through contamination
  • To prevent alteration of samples/results in laboratory settings
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2
Q

Sterilization

A

Killing all microbes present

Including spores

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3
Q

Disinfection

A

Removal of vegetative of pathogens from inanimate objects

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4
Q

Sanitization

A

reduction in number of microbes from inanimate objects present to safe (accepted) public health levels
By mechanical cleansing and physical methods
Ex: baby bottles

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5
Q

Sepsis

A

growth of microbes (presence of toxins) in tissue

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6
Q

Asepsis

A

techniques that prevent the entry of microorganisms into sterile tissue
Ex: washing, NO chemicals

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7
Q

Antisepsis

A

Application of chemicals to body surfaces to kill or inhibit microbes
Doesn’t cause damage to tissue
Ex: using chemical antiseptics

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8
Q

Aseptic Technique

A

Methods applied to an object or area to prevent microbial (pathogenic) contamination

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9
Q

Degerming

A

Cleansing techniques to remove transient microbes and debris from living tissue
Ex: showering

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10
Q

Bacteriocide

A

Chemicals that kill vegatative cells and may NOT kill the spores
“cide”: chemical that kills

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11
Q

Bacteriostat

A

Chemicals that stop or slow microbial growth

“stat”: prevents multiplication

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12
Q

Factors that Influence Microbial Control

A
  • The number of microorganisms
  • The type of microorganisms
  • The nature of the suspending medium
    - Determine the nature of the chemicals
  • Time
  • Temperature
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13
Q

Types of Cellular Injury

A
  • Alteration of membrane permeability
    • Damage to cell wall
    • Damage cell membrane
  • Damage to proteins
  • Damage to nucleic acids
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14
Q

Heat

A
  • Most common method
  • Most effective method
  • Least expensive method
  • Mode of action:
    • Denaturing proteins (enzymes) of coagulation
      ex: autoclave
    • Oxidizing of microorganisms
      ex: burning
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15
Q

Thermal Death Point (TDP)

A

*Lowest temperature at which all the microorganisms in a liquid suspension will be killed in 10 minutes

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16
Q

Thermal Death Time(TDT)

A

*Minimal length of time for all the microorganisms in a liquid suspension to be killed at a given temperature

17
Q

Moist Heat–Autoclave

A

*Steam under pressure
*121 degrees C at 15 psi for 15-20 mins
*Destroys all forms-STERILIZATION
Test by: spore strips and heat sensitive paper

18
Q

Moist Heat–Boiling

A

*98-100oC for 30 min
*Kills most vegetative cells not heat resistant forms
Ex: Sanitizing

19
Q

Moist Heat–Tyndallization (Fractional Sterilization)

A

*Heating to 100oC for 30 min
*For 3 successive days
*Over night incubation periods in between
Ex: boil-sit and cool-boil-sit and cool etc

20
Q

Moist Heat–Pasteurization

A
  • Heating material at specific temp for a specific length of time and cool rapidly
  • Temp. selection is based upon most resistant pathogen to be destroyed
    • Coxiella Burnetti
  • High Temp Short Term (HTST)
    • 72oC for 15 sec
  • Ultrahigh Temp (UHT)
    • 140oC for 1-2 sec
21
Q

Dry Heat–Hot Air Ovens

A
  • 160-170oC for 2-3 hrs
  • Oxidation of microbes
  • Sterilizes
22
Q

Dry Heat–Incineration’s (Direct Flame)

A
  • Oxidation to ashes (burning) 1-60 minutes

* Temp may exceed 1000oC

23
Q

Radiation

A
  • Two types exist

* Rays less than 300 mm are effective for sterilization

24
Q

Radiation–Ionizing rays (X-rays, gamma rays)

A
  • Produces hyperactive ions and free radicals

* Destruction to DNA, denatures proteins

25
Q

Radiation– Non-ionizing Rays (UV Light)

A

*Damage to DNA (Thymine dimers)

26
Q

Preservation–Low Temp

A
  • Bacteriostatic effect (slows down replication)
  • Not effective against Psychrophiles
  • Usually effective against pathogens
27
Q

Preservation–Dessication

A
  • Involves the removal of moisture
  • Effectiveness varies
  • Bacteriostatic
28
Q

Preservation–Lyophilization

A

*Freeze drying

29
Q

Preservation

A
  • Increased osmotic pressure
    • High concentration of salt, sugar
    • Dehydrates cells
    • More effective against bacteria than fungi
30
Q

Filtration

A
  • Passage of material through filters with extremely small pores (appropriate size)
    • Solids
    • Heat-liable liquids
    • Drinks
    • Air
31
Q

Physical Cleaning

A
  • Ultrasonic
    • High frequency wavelength of sound
    • Physically disrupts cellular integrity
  • Hand Washing
    • Time and kind of soaps are important factors in effectiveness

Microbial Control (1 decks)

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