Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MICR2208 > 16 - Microbial Death > Flashcards

16 - Microbial Death Flashcards

1
Q

Sterilisation

A

Process that removes or kills ALL living organisms. Physical or chemical agents (heat, electromagnetic radiation, filters and sterilants)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Disinfection

A

Treatment of materials with disinfectants to kill, inhibit or remove disease causing microorganisms. May be residual living organisms after treatment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Disinfectants

A

Chemicals employed to kill, inhibit or remove microorganisms present on inanimate objects. Harsh, not used to decontaminate plants or animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Sanitisation

A

Reduction of microbial population on inanimate object to low level (safe by public health standards). Physical or chemical agents (e.g. cleaning cutlery)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Antiseptics

A

Chemical agents applied to tissue/body surfaces to prevent infection by killing pathogens. Mild to avoid tissue damage (alcohol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Aseptic technique

A

Procedures to prevent contamination of previously uncontaminated materials to obtain pure cultures of microorganisms and to prevent infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Chemotherapy

A

Use of chemical agents to kill or inhibit growth of microorganisms within host tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Bactericidal

A

Kills bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Bacteriostatic

A

Inhibits bacterial growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Viricidal

A

Kills viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Fungicidal

A

Kills fungi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Fungistatic

A

Inhibits fungal growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Algicidal

A

Kills algae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Antimicrobial

A

Kills microbes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Selective toxicity

A

Activity against microbial pathogen but damages the host as little as possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Chemotherapeutic

A

Antimicrobial agent with selective toxicity. Compound used in treatment of disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Decimal reduction time (D value)

A

The time value required to kill 90% of the microbes in a sample under specified conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

6 factors influencing the effectiveness of control agents

A
  1. Population size
  2. Contact time
  3. Population susceptibility
  4. Antimicrobial concentration
  5. Temperature
  6. Local environment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Population size

A

The larger the size of the population, the longer it takes to achieve sterility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Contact time

A

The longer a population is exposed to a microbicidal agent, the more organisms are killed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Population susceptibility

A
  • Endospores are more resistant than vegetative forms of their organism
  • Actively growing log phase bacteria are more susceptible than stationary phase cells due to increased uptake of agent
  • Acid fast bacteria are more resistant
  • Gram negative are more resistant than gram positive
22
Q

Antimicrobial concentration

A
  • The more concentrated a chemical agent or intense a physical agent, the more rapidly organisms are destroyed
  • Some agents more effective at lower concentrations (70% ethanol more effective than 95% ethanol)
23
Q

Temperature

A
  • Mild heat enhances activity of chemical disinfectants by promoting chemical reactions
  • 10ºC rise in temp increases disinfectant activity 2 to 3 fold
24
Q

Local environment

A

Some environmental factors are protective, others contribute to killing. (e.g. organic matter can protect microorganisms)

25
Q

Examples of physical methods in control

A
  • Heat
  • Radiation
  • Filtration
  • Low temperatures
26
Q

Heat

A

Kills by:
- Denaturing proteins and nucleic acid degradation
- Membrane becomes more fluid so contents leak out, membrane potential lost preventing nutrient transport

27
Q

Types of heat

A
  • Dry heat (dehydrates the cell, greater amount of heat required than moist) e.g. Incineration (flaming) and Hot air ovens
  • Moist heat (Steam sterilisation, boiling, cooking and pasteurisation)- more effective
28
Q

Hot air ovens (dry heat)

A

For glassware and metal instruments.
- Advantages: Does not corrode so can be used for glassware and metal
- Disadvantages: Slow, not suitable for heat sensitive materials like rubber

29
Q

Steam sterilisation (moist heat)

A
  • Carried out by autoclave.
  • Increase in steam temp is proportional to pressure
  • Used for media, liquids, bandages
  • Advantages: fast, convenient and reliable
  • Disadvantages: corrodes metal, leaves glassware wet, damage to heat sensitive items
30
Q

boiling (moist heat)

A

Kills vegetative cells and eukaryotic spores. Will not destroy bacterial endospores therefore not a sterilant

31
Q

Cooking (moist heat)

A

Kills all but spores

32
Q

Pasteurisation (moist heat)

A
  • Reduces microbial population of liquid.
  • Extends shelf life of products (reduces spoilage) but does not sterilise (except UHT)
  • heat liquids under 100C killing disease causing microbes without cooking the liquids
33
Q

Types of pasteurisation

A
  • Batch pasteurisation: in large tanks, used for beer and fruit juice
  • Ultrahigh temp: ~140ºC for 3 seconds. No refrigeration needed and product is stored at room temp. Used for milk
  • high temperature short time (continuous flow): Liquid forced through metal plates or pipes. Used for milk and dairy products to be stored in fridge
34
Q

Types of radiation

A
  • ionising radiation
  • UV light
35
Q

Ionising radiation

A
  • e.g. X rays and gamma rays
  • Damage cell by reacting with proteins and nucleic acids
  • used for heat sensitive medical supplies (plastic syringes, ABs, drugs, food)
  • Advantages: penetrates deeply, kills all cells (including endospores), very effective
  • Disadvantages: Expensive and dangerous
36
Q

UV light

A
  • Electromagnetic radiation absorbed by nucleic acids altering DNA structure (thymine dimers)
  • T dimer distorts DNA, preventing replication
  • Used to disinfect air in rooms, water treatment and biological safety cabinets
  • Advantages: Easy to use, can disinfect an area
  • Disadvantages: Does not penetrate glass, liquid or opaque solids
37
Q

filtration

A
  • used for culture media, oil, pharmaceuticals (e.g. safety cabinet, N95 masks)
38
Q

Types of filtration

A
  • Depth filters: Fibrous material excludes bacteria and large microorganisms
  • Membrane filters: Solution forced through filter why vacuum or syringe. 0.2 and 0.45 micrometers common size. made with cellulose acetate
39
Q

Factors influencing effectiveness of chemical control

A
  • concentration and nature of disinfectant
  • length of treatment
  • kind of microorganisms present (TB, colds and polio resistant)
40
Q

Types of chemical control agents that denature proteins and disrupt cells membranes

A
  1. phenols
  2. alcohols
  3. quarternary ammonium compounds
41
Q

Phenols

A
  • Lysol and triclosan
  • Advantages: Effectives in presence of organic matter, long lasting, good for disinfecting pus, saliva, faeces. Tuberculocidal
  • Disadvantages: Strong odour, irritating to skin, not sporadical
42
Q

Alcohols

A
  • Ethanol and isopropanol
  • Advantages: Antiseptic, cheap, stable, nontoxic
  • Disadvantages: not sporadical
43
Q

Why is 70% ethanol more effective than 100%

A

100% is dehydrating agent, can extract cellular water and preserve cells

44
Q

Halogens

A
  • Chlorine:
    D: high affinity for organic matter, too harsh for antiseptic.
    A: Very effective in water supplies and food industries
  • iodine:
    A: Sporadical at high concentrations
    D: May damage skin, leave stain and cause allergic response
  • Betadine: water soluble, stable, nonstaining, releases iodine slowly to minimise skin burns and irritation
45
Q

Heavy metals

A
  • Silver nitrate: antiseptic on newborns, prevents eye infection
  • Copper sulfate: algicidal and fungicidial
46
Q

Quaternary ammonium compounds

A
  • Cation detergents
  • Detergents: have both hydrophilic and phobic ends.
  • e.g. Zephiran
  • Advantages: stable and nontoxic used and food and antiseptics
  • Disadvantages: inactivated by hard water and soap. Not sporadical
47
Q

Aldehydes

A
  • Formaldehyde and Glutaraldehyde (chemical sterilant)
  • Sporicidal, tuberculocidal, virucidal, bactericidal, fungicidal
48
Q

Sterilising gases

A
  • Ethylene oxide: Sporicidal, tuberculocidal, virucidal, bactericidal, fungicidal. Penetrates packing materials, suitable for heat sensitive items (spacecraft). D: Expensive, toxic and flammable
  • Vaporised hydrogen peroxide: Decontaminate operating rooms and large facilities
49
Q

Advantages of filtration

A

effective and economical for
liquids and gases which cannot be autoclaved: e.g. thermolabile liquids

50
Q

Disadvantages of Filtration

A

Mycoplasma - small, can
squeeze through pores; VIRUSES can pass
also through 0.2µm pores, so solutions are
not necessarily “sterile”.

51
Q

Chemical control agents that chemically modify cell constituents

A
  1. aldehydes
  2. halogens
  3. sterilising agents
  4. metals

MICR2208 (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions