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Microbiology > Sterilization And Disinfection > Flashcards

Sterilization And Disinfection Flashcards

1
Q

– the process by which most bacterial forms in non-living objects are destroyed, without necessarily destroying saprophytes and bacterial spores

A

DISINFECTION

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2
Q

refers to the use of chemical agents on skin or living tissues to inhibit or eliminate disease producing microorganism

A

Antisepsis

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3
Q

a gradual process and the kinetics of death are exponential

A

Heat

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4
Q

the relationship between sterilization and the temperature of exposure is expressed in terms of

A

Thermal death time

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5
Q

the time required to kill a suspension of microorganism at a predetermined temperature in a specified environment

A

Thermal death time

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6
Q

MECHANISMS OF THERMAL INJURY

A
  1. strand breaks in the bacterial DNA
  2. Loss of integrity of the membrane
  3. Denaturation of proteins
  4. Oxidative damage
  5. elevated levels of electrolytes
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7
Q

Preferred over dry heat because of its more rapid killing action

A

Moist heat

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8
Q

In moist heat

destroyed at 120 0C for 4 mins or 5.5 hrs at 100 0C

A

Endospores

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9
Q

Kills all vegetative forms of microorganisms at 80 – 100 C but not bacterial spores

A

Boiling

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10
Q
  • Used to sterilize materials that would be damaged by autoclaving
  • The material to be sterilized is exposed to live steam for 30 mins for 3 consecutive days
A

FRACTIONAL STERILIZATION (TYNDALLIZATION)

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11
Q
  • used in the processing of milk, foods and other beverages

- only inactivate disease producing microorganisms

A

Pasteurization

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12
Q

Expose milk at high temperature of _________followed by rapid cooling

A

60-65c

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13
Q

-Used in the sterilization of surgical instruments and bandages, culture media and other contaminated
materials

A

Steam under pressure (auto calving)

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14
Q
  1. STEAM UNDER PRESSURE (AUTOCLAVING)

- the steam is confined in a closed vessel pressure

A

reaches 15 psi  121 0C

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15
Q

How many minutes to sterilize the material in autoclave

A

15-20 minutes

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16
Q
  • requires higher temperature and longer period of exposure

- effectiveness depends on the ability of heat to penetrate the material to be sterilized

A

Dry heat

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17
Q

Most widely used type of dry heat

A

hot air oven

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18
Q

Dry heat use to sterilize

A

powders,
oils,
jellies and
glassware

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19
Q

Other useful forms of dry heat

A

a. incineration

b. open flame

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20
Q

oDeprive the organism of moisture
oBacterial spores are not destroyed
oUsed in the preservation of foods

A

Desiccation or drying

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21
Q

oNot reliable because spores are not destroyed

oMany microorganisms can survive low temperatures

A

Freezing

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22
Q

– a technique of preserving microorganisms by rapid freezing and dehydrating it in high vacuum and stored under vacuum in sealed ampule in cold storage

A

LYOPHILIZATION

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23
Q

A.ULTRAVIOLET LIGHT (UVL)

oMost effective wavelength =

A

240-280 nm

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24
Q

Ultra violet oOptimum wavelength

A

260nm

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25
Q

Radiation mechanism of actions

A

disrupts H bonds in microbial cell
 formation of thymine dimers
lethal frameshift mutations

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26
Q

oUsed in sterilization of enclosed areas

A

Ultra violet light

27
Q

oHas greater penetrating ability than UVL

oPotentially hazardous to human cells

A

Ionizing radiation

28
Q

Ionizing radiation mechanism of actions

A

formation of free radicals
 chemically interact with proteins & nucleic acids
 cell death

29
Q

oForm of mechanical sieving  physical separation of microorganisms from the fluid

A

Filtration

30
Q

oUtilizes cellulose ester filters

A

Filtration

31
Q

Filtration

o0.22 um pore size – can filter almost all microorganisms EXCEPT

A

viruses,
Mycoplasma,
Chlamydia &
Rickettsia

32
Q

oBased on the principle of osmosis

A

Osmotic pressure

33
Q

Mechanism of action of osmotic pressure

A

When the concentration of the solution surrounding the bacterial cell is altered  collapse of the bacterial cell or may become
turgid

34
Q

Mechanism of ultrasonic vibration

A 
passage of sound through the liquid 
    produce alternating pressures 
    cavities form in the liquid 
 cavities    grow in size 
 burst 
 cells    disintegrate
35
Q

FACTORS AFFECTING DISINFECTION

A
  1. Concentration of chemical agent
  2. Time
  3. Temperature
  4. pH
  5. Nature of the medium
  6. Nature of the organism
36
Q

used as the standard in the evaluation of new chemical agents

37
Q

designed to determine the ratio of the highest dilution that will kill the organism within a specified time to the greatest dilution of phenol showing the same result

A

Dilution test

38
Q

MECHANISMS OF ACTION OF CHEMICAL AGENTS

Interfere with normal membrane function  release of small metabolites and interfere with active transport and energy metabolism

A

Damage of the cell membrane

39
Q

– quarternary ammonium compounds

  • cause disruption of membrane & loss of membrane permeability
  • denatures proteins
  • most effective at alkaline pH
A

Cationic agents

40
Q
  • cause disruption of lipoprotein framework of the membrane
    - most effective at acid ph
    - e.g. soaps & detergents
A

Anioinic agents

41
Q
  • cause leakage of cell contents

- includes phenol and cresol

A

Phenolic compounds

42
Q

highly toxic to human cell

43
Q

– phenol derivative

   - less toxic & more potent than phenol
   - e.g. lysol & creolin
44
Q

disorganize lipid structure by penetrating into the hydrocarbon region

45
Q

AGENTS THAT DENATURE PROTEINS

A

a. acids & alkalis – alters the pH of the organism’s environment
b. alcohol & acetone
c. phenol & its derivatives

46
Q

poison the enzyme activity by forming mercaptides with the SH groups of cysteine residues

A

Heavy metals

47
Q

useful as antiseptics but not as disinfectants

A

Mercurials

48
Q

bactericidal

A

Silver compounds

49
Q

used in Crede’s prophylaxis

A

Silver nitrate

50
Q

used in burn patients

A

Silver sulfadiazine

51
Q

inactivates enzymes by converting functional SH groups to oxidized S-S form

A

Oxidizing agents

52
Q

Oxidizing agents includes

A
  1. Halogens

2. Hydrogen peroxide

53
Q

Halogens

A

Iodine

Chlorine

54
Q

– considered the best antiseptic

- bactericidal, sporicidal, fungicidal, virucidal & amoebicidal

55
Q

– used as water disinfectant

- used in sanitizing food & dairy processing equipments

56
Q

– weak antiseptic

- used in cleansing of wounds, surgical devices & contact lenses

A

Hydrogen peroxide

57
Q
  • used in the treatment of dermatologic lesions

- used in staining bacteria

58
Q

a. – highly selective for gram (+) bacteria

e. g. crystal violet, malachite green

A

triphenymethane dyes

59
Q

A kind of dye used as wound antiseptics

60
Q

Alkylating agents

A

Formaldehyde
Glutareldehyd
Ethelyne oxide

61
Q
  • sporicidal
    -used in preserving specimens &in the preparation of vaccines
    • used to destroy M. tuberculosis in sputum & fungus in athlete’s foot
    • used in the treatment of
      textiles
A

Formaldehyde

62
Q
  • sporicidal
    - 10 times more effective than formaldehyde
    - used as cold sterilant for surgical instruments especially respiratory therapy instruments
A

Glutaraldehyde

63
Q
  • sporicidal
    - used in gaseous sterilization of materials that would be damaged by heat like polyethylene tubes, electronic & medical equipments, biologicals & drugs
    - slow acting
A

Ethylene oxide

64
Q

– the process of completely destroying all microbial forms, including bacterial spores

A

STERILIZATION

Microbiology (6 decks)

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