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Microbiology > Sterilization And Disinfection > Flashcards

Sterilization And Disinfection Flashcards

(64 cards)

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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
Radiation mechanism of actions
disrupts H bonds in microbial cell  formation of thymine dimers lethal frameshift mutations
26
oUsed in sterilization of enclosed areas
Ultra violet light
27
oHas greater penetrating ability than UVL | oPotentially hazardous to human cells
Ionizing radiation
28
Ionizing radiation mechanism of actions
formation of free radicals  chemically interact with proteins & nucleic acids  cell death
29
oForm of mechanical sieving  physical separation of microorganisms from the fluid
Filtration
30
oUtilizes cellulose ester filters
Filtration
31
Filtration o0.22 um pore size – can filter almost all microorganisms EXCEPT
viruses, Mycoplasma, Chlamydia & Rickettsia
32
oBased on the principle of osmosis
Osmotic pressure
33
Mechanism of action of osmotic pressure
When the concentration of the solution surrounding the bacterial cell is altered  collapse of the bacterial cell or may become turgid
34
Mechanism of ultrasonic vibration
``` passage of sound through the liquid  produce alternating pressures  cavities form in the liquid  cavities grow in size  burst  cells disintegrate ```
35
FACTORS AFFECTING DISINFECTION
1. Concentration of chemical agent 2. Time 3. Temperature 4. pH 5. Nature of the medium 6. Nature of the organism
36
used as the standard in the evaluation of new chemical agents
Phenol
37
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
Dilution test
38
MECHANISMS OF ACTION OF CHEMICAL AGENTS Interfere with normal membrane function  release of small metabolites and interfere with active transport and energy metabolism
Damage of the cell membrane
39
– quarternary ammonium compounds - cause disruption of membrane & loss of membrane permeability - denatures proteins - most effective at alkaline pH
Cationic agents
40
- cause disruption of lipoprotein framework of the membrane - most effective at acid ph - e.g. soaps & detergents
Anioinic agents
41
- cause leakage of cell contents | - includes phenol and cresol
Phenolic compounds
42
highly toxic to human cell
Phenol
43
– phenol derivative - less toxic & more potent than phenol - e.g. lysol & creolin
Cresol
44
disorganize lipid structure by penetrating into the hydrocarbon region
Alcohol
45
AGENTS THAT DENATURE PROTEINS
a. acids & alkalis – alters the pH of the organism’s environment b. alcohol & acetone c. phenol & its derivatives
46
poison the enzyme activity by forming mercaptides with the SH groups of cysteine residues
Heavy metals
47
useful as antiseptics but not as disinfectants
Mercurials
48
bactericidal
Silver compounds
49
used in Crede’s prophylaxis
Silver nitrate
50
used in burn patients
Silver sulfadiazine
51
inactivates enzymes by converting functional SH groups to oxidized S-S form
Oxidizing agents
52
Oxidizing agents includes
1. Halogens | 2. Hydrogen peroxide
53
Halogens
Iodine | Chlorine
54
– considered the best antiseptic | - bactericidal, sporicidal, fungicidal, virucidal & amoebicidal
Iodine
55
– used as water disinfectant | - used in sanitizing food & dairy processing equipments
Chlorine
56
– weak antiseptic | - used in cleansing of wounds, surgical devices & contact lenses
Hydrogen peroxide
57
- used in the treatment of dermatologic lesions | - used in staining bacteria
Dyes
58
a. – highly selective for gram (+) bacteria | e. g. crystal violet, malachite green
triphenymethane dyes
59
A kind of dye used as wound antiseptics
acridines
60
Alkylating agents
Formaldehyde Glutareldehyd Ethelyne oxide
61
- 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
Formaldehyde
62
- sporicidal - 10 times more effective than formaldehyde - used as cold sterilant for surgical instruments especially respiratory therapy instruments
Glutaraldehyde
63
- sporicidal - used in gaseous sterilization of materials that would be damaged by heat like polyethylene tubes, electronic & medical equipments, biologicals & drugs - slow acting
Ethylene oxide
64
– the process of completely destroying all microbial forms, including bacterial spores
STERILIZATION

Microbiology (6 decks)

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