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micrb 265 > week 5 > Flashcards

week 5 Flashcards

1
Q

Microorganisms are not killed

A

instantly

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2
Q

Population death usually occurs

A

exponentially

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3
Q

Measure of agent’s killing efficiency

A

Decimal reduction time

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4
Q

Decimal reduction time

A

time to kill 90% (reduce [bacteria] by 1 log unit)

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5
Q

what to ensure for killing efficiency

A

Must be sure persister cells (viable but nonculturable/VBNC condition) are dead

Once they recover they may regain the ability to reproduce and cause infection

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6
Q

Reversible and irreversible

A

Reversible: Bacteriostatic
Irreversible: bactericidal, bacteriolytic

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7
Q 
Bacteriostatic:
Bactericidal: 
Bacteriolytic: 
Optical density: 
Viable cell count:
A

Bacteriostatic: just stop growth of cells
Bactericidal: kills cells but doesn’t lyse them
Bacteriolytic: kills and lyses cells
Optical density: Bacteriostatic and bactericidal are the same
Viable cell count: bactericidal and bacteriolytic are the same

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8
Q

Methods for killing microbial cells (5)

A 
sterilization
Disinfection/Disinfectants
Sanitization
Antisepsis
Chemotherapy (antibiotics)
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9
Q 
sterilization
Disinfection
Disinfectants
Sanitization
Antisepsis
Chemotherapy (antibiotics)
A

sterilization: destruction or removal of all viable organisms (no bacteria)
Disinfection: killing, inhibition, or removal of disease causing (pathogenic) organisms but not endospores
Disinfectants: usually used on inanimate objects
Sanitization: reduction of microbial population to levels deemed safe (based on public health’s standards)
Antisepsis: prevention of infection of living tissue by microorganisms
Chemical agents that kill or inhibit growth of microorganisms when applied to surface of tissue
Chemotherapy (antibiotics): kill or inhibit internal microorganisms

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10
Q

Physical methods

Chemical methods

Mechanical methods

Biological methods

A

Physical methods
Heat
Radiation

Chemical methods
Gas
Liquids

Mechanical methods
Filtration

Biological methods
Antimicrobials

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11
Q

high moist heat

A

Destroys viruses, fungi and bacteria (including endospores)

Autoclaving

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12
Q

Low moist heat

A

(pasteurization)
Controlled heating at temperatures well below boiling
Used for milk, beer, other beverages
Process does not sterilize but does kill pathogens present and slow spoilage by reducing the total load of organisms present

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13
Q

UV radiation most bactericidal

A

260nm is most bactericidal since it is absorbed by DNA

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14
Q

effect of UV radiation

A

Causes thymine dimers which prevent replication and transcription

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15
Q

UV limited to

A

UV limited to surface sterilization because it doesn’t penetrate glass, dirt films, water and other substances
Has been used for water treatment

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16
Q

how deep does Gamma radiation penetrate and what does it produce (3)

A

Penetrates deep into objects

Generates double stranded breaks in DNA, reactive oxygen species, membrane damage

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17
Q

deadliness of gamma radiation

A

Kills living organisms, as well as bacterial endospores; not always effects against viruses (depends on outer coating of virus)
Used for sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies and food

18
Q

what is membrane filtration,

how does it work and for what type of samples

A

passing a solution through a filter membrane under a vacuum to remove microbes

  • used for liquid samples
  • similar to collecting bacteria from water
19
Q

what’s HEPA filter, how does it work, for what type of sample

A

another form of membrane filtration but for air instead

  • high-efficiency particulate air
  • used for gaseous samples
20
Q

phenolics commonly used as

A

laboratory

and hospital disinfectants

21
Q

how do phenolics work

A

denaturing proteins
and disrupting cell
membranes

22
Q

what do phenolics kill

A

bacteria, including
Mycobacterium tuberculosis,
fungi and enveloped viruses

Does not kill spores

23
Q

phenolics effectivity + duration

odor + skin effects

A

Effective in presence of
organic material, and long lasting
bad smell, skin irritant

24
Q

phenolics example

A

triclosan

25
Q

alcohol usage, what does it kill

A

Among the most widely used
disinfectants and antiseptics
Bactericidal, fungicidal, but not sporicidal
Kills enveloped viruses

26
Q

how does alcohol work

A

Denature proteins and possibly dissolve membrane lipids

27
Q

alcohol example

A

ethanol, isopropanol

28
Q

why is 70% alcohol better than 100%

A

100% too dry - will dry out bacteria and if it comes in contact with water will come alive again

29
Q

what is Halogens used for

A

Skin antiseptic

30
Q

how do Halogens kill

A

Oxidizes cell constituents and iodinates proteins

31
Q

what do Halogens kill

A

Kills bacteria, fungi, viruses

At high concentrations may kill spores

32
Q

problems with Halogens

A

Skin damage, staining, and

allergies can be a problem

33
Q

Halogens eg

A

halazone, triiodide (wants to move to anything with double bond)

34
Q

how do aldehydes work

A

Crosslink proteins

• Stop metabolic activity

35
Q

what do Aldehydes kill

A

Kills most bacteria and

fungi, including spores

36
Q

Aldehydes eg

A

formaldehyde, gluteraldehyde

37
Q

what are Quaternary ammonium

compounds used for

A

detergents that have antimicrobial
activity and are effective
disinfectants

38
Q

what do Quaternary ammonium

compounds kill

A

kill most bacteria, but not M.
tuberculosis or endospores
• kills enveloped viruses, some fungi

39
Q

safety and inactivation of Quaternary ammonium

compounds

A

safe and easy to use,

• inactivated by hard water and soap (hard water has many minerals causing it to precipitate)

40
Q

Quaternary ammonium

compounds eg

A

Cetylpyridinium chloride (amphipathic), Benzalkonium chloride

41
Q

what does Hydrogen peroxide kill

A

Kills most viruses, bacteria and fungi

42
Q

how does Hydrogen peroxide work

A

Oxidized proteins, lipids, and sugars

micrb 265 (4 decks)

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