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CBE 2290 > Module 5 > Flashcards

Module 5 Flashcards

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1
Q

What is sterilization?

A

destruction/removal of all viable organisms, spores and acellular entitues (viruses)

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2
Q

What is disinfection?

A

kills, inhibits or removes microorganisms that may cause disease (not spores)

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3
Q

What is the difference between disinfection and sterilization?

A

Disinfection: kills, inhibits or removes microorganisms, typically targeting most vegetative cells, BUT NOT SPORES

Sterilization: eliminates all viable organisms and spores

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4
Q

What are disinfectants?

A

agents (often chemicals) used for the treatment of inanimate objects to kill or inhibit pathogenic microorganisms

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5
Q

What is antisepsis

A

agents that prevent infection by destruction or inhibition of microorganisms on living tissues

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6
Q

Whats more toxic: antisepsis or disinfection and why

A

disinfectants because antisepsis has chemical agents that can be applied to tissues without causing damage

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7
Q

What is sanitization?

A

reduces microbial populations to safe levels based on public health standards

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8
Q

what is chemotherapy?

A

use of chemical agents to kill/inhibit microorganism growth in host tissues

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9
Q

What are cidal agents?

A

kills pathogens and many non-pathogens but not necessarily spores

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10
Q

What are examples (3) of cidal agents?

A
  1. bactericides
  2. fungicides
  3. viricides
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11
Q

What are static agents

A

prevent growth of microorganisms when present

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12
Q

What are examples (2) of static agents?

A
  1. bacteriostatic agents
  2. fungistatic agents
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13
Q

What is a bacterial endospore?

A

a dormant stage formed by some bacteria that provides protection against various harsh conditions

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14
Q

What 6 conditions influence the effectiveness of antimicrobial agents?

A
  1. temp
  2. local environment
  3. contact time
  4. concentration/intensity
  5. population size
  6. population composition
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15
Q

Why are bacterial endospores considered a challenge in microbiology?

A

because they are highly resistant and can survive extreme conditions, making them difficult to eliminate

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16
Q

How does microbial population death occur after exposure to a lethal agent?

A

occurs exponentially, meaning it doesn’t happen instantly but rather decreases rapidly over time

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17
Q

What happens to the killing rate of a microbial population as it decreases?

A

the killing rate may slow if there is a more resistant strain present

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18
Q

Why is it important to measure the killing efficiency of a microbial agent?

A

important to understand its effectiveness and ensure it can properly reduce or eliminate populations, especially resistant strains

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19
Q

What is Decimal Reduction Time (D-value)?

A

time required to kill 90% of microbes or spores under specified conditions

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20
Q

What is the Z-value?

A

measure of the temperature sensitivity of an organism
- indicating the temp change that will cause the D-Value to change by a factor of 10

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21
Q

Why is it important to confirm the death of a viable but non-culturable (VBNC) cell?

A

because if they recover, they may regain the ability to reproduce and potentially cause infection or contamination

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22
Q

What are 3 types of control

A
  1. mechanical/physical control methods
  2. chemical
  3. antimicrobial chemo (drugs)
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23
Q

What is antimicrobial chemotherapy?

A

use of drugs to kill or inhibit the growth of microorganisms

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24
Q

Why is boiling water not sufficient for sterilization?

A

will not destroy bacterial spores, so it disinfects not sterilizes

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25
What are examples of mechanical/physical control methods
heat, filtration, radiation
26
what are examples of chemical control methods
disinfectants, antiseptics
27
what does moist heat sterilization do?
1. degrades nucleic acids 2. denatures pr 3. disrupts membranes
28
What conditions are necessary for moist heat sterilization?
- must be done at temp greater than 100C - using saturated steam under pressure in an autoclave - both temperature and time is important
29
is moist heat sterilization effective against spores?
YES
30
What is a critical aspect of quality control in sterilization?
ensures that the sterilization process is effective, confirming that all microorganisms, including spores, are killed
31
What is the primary purpose of pasteurization?
used to kill pathogens and slow spoilage by reducing the total load of organisms WITHOUT sterilizing the product
32
What are the conditions for flash pasteurization (HTST)?
- heating liquid to 72C for 15 seconds, followed by rapid cooling - extends milk shelf life to 2-3 weeks
33
What is ultrahigh-temperature (UHT) pasteurization?
- heating at 140-150C for 1-3 seconds - extends milk shelf life to 6-9 months
34
What are 3 effects of low temp
1. freezing stops cell reproduction bc of lack of liquid water 2. some cells killed by ice crystal disruption of cell membranes 3. refrigeration slows cell growth
35
What effect does freezing have on microbial cells?
stops cell reproduction due to the lack of liquid water - some cells may be killed by ice crystal disruption of cell membranes
36
How does refrigeration affect microbial growth?
slows down microbial growth by reducing metabolic activity, thereby prolonging the freshness of food
37
What are the conditions for dry heat sterilization?
- requires higher temp (160-170C) - longer exposure time (2-3 hours)
38
TRUE OR FALSE: dry heat sterilization is used in the presence of water
FALSE
39
What is dry heat sterilization used for
glassware, metal instruments
40
Why is dry heat sterilization less effective
- requires higher temp - longer exporsure time
41
What are 4 advantages of dry heat sterilization
1. avoids corrosion 2. oxidation of cell constituents 3. pr- denaturation 4. potential use of incineration or dry ovens
42
What is filtration?
- reduces population in heat sensitive fluids - sterilizes various liquids and gases
43
TRUE OR FALSE: filtration CANNOT physically remove microorganisms
FALSE
44
What are depth filters?
thick fibrous/granular material bonded to thick later with twisting channels of small diameter
45
how do depth filters remove cells
physical screening, entrapment and or absorption to surface of filter material
46
What are membrane filters and what is their pore size?
porous membranes with defined pore sizes that remove most vegetative cells but not viruses (~ 0.1 mm thick)
47
How do membrane filters remove cells?
physical screening
48
How would you verify that the filtration had removed all microorganisms?
perform a challenge test by passing microorganisms through a filter, culturing the filtrate and checking for any growth
49
What is the filtration efficiency of an N-95 surgical mask?
the mask excludes 95% of particles larger than 0.3um
50
What is a common use of cotton plugs in microbiology?
cotton plugs are used on culture vessels to prevent contamination by filtering out particles from the air
51
What are high-efficiency particulate air (HEPA) filters and how efficient are they?
- fiberglass depth filters - remove 99.97% of particles that are ≥ 0.3um in size through physical retention and electrostatic interactions
52
Can HEPA filters remove viruses smaller than 0.1um?
yes, depending on the filters design
53
Where are HEPA filters commonly used?
- laminar flow biological safety cabinets - clean rooms
54
What happens to radiation energy as wavelength decreases?
as wavelength decreases, radiation energy increases
55
Rank the energy of different types of radiation: - gamma rays - X-rays - visible light - infrared
1. (highest) = gamma rays and X-rays 2. visible light 3. (lowest) = infrared
56
does UV radiation kill spores? Why or why not?
no because its a disinfectant method.
57
At what wavelength is UV radiation most bactericidal? Why?
- 260 nm - because it is most effectively absorbed by DNA, causing thymine dimers, which prevent DNA replication and transcription
58
What effect does UV radiation at 325-400 nm have on tryptophan?
- induce tryptophan breakdown, producing toxic photoproducts that cause further DNA damage
59
What are the limitations of UV radiation for sterilization?
limited to surface treatment because of its poor penetration of materials like glass, dirt films and water
60
Where is UV radiation commonly used for decontamination?
- water treatment - biological safety cabinets - clean rooms
61
What is gamma radiation?
excellent sterilizing agent, penetrates deep into objects
62
How does gamma radiation work as a sterilizing agent?
it damages DNA and can polymerize some molecules
63
can gamma radiation kill endospores?
yes
64
can gamma radiation destroy viruses
sometimes but not always effective
65
What is gamma radiation used for in sterilization?
cold sterilization of antibiotics, hormones, sutures, plastic disposable supplies, and foods
66
Where are disinfectants used
outside the body, primarily on inanimate surfaces to kill or inhibit infectious agents
67
What are the 4 key properties a disinfectant must have?
1. effective against a wide variety of infectious agents at low concentrations 2. have low toxicity to animals 3. effective in the presence of organic matter 4. stable in storage
68
What can the overuse of antiseptics like triclosan lead to?
may increase the frequency of antibiotic resistance
69
What is Ethylene Oxide (EtO) used for in sterilization?
sterilizing heat-sensitive materials such as disposable plastic products, sutures, etc.
70
How does Ethylene Oxide (EtO) sterilize materials?
EtO is a strong alkylating agent that reacts with functional groups on DNA and pr-, blocking replication and enzyme function - kills spores
71
What factors influence the effectiveness of Ethylene Oxide (EtO) sterilization?
depends on - concentration - humidity - temperature
72
What are the typical conditions of Ethylene Oxide (EtO) sterilization?
- 5-8 hours - 38C - 40-50% humidity
73
What is the goal of antimicrobial chemotherapy?
uses chemical agents to treat diseases by selectively killing or inhibiting microbial pathogens with minimal damages to the host
74
What is selective toxicity in antimicrobial chemo?
refers to the ability of an antimicrobial agent to kill or inhibit microbial pathogens while causing little or no damage to the host
75
What is the difference between natural and semi-synthetic antibiotics?
Natural: directly produced by microorganisms Semi: chemically modified derivatives of natural antibiotics
76
What is the therapeutic index?
ratio of toxic dose to therapeutic dose
77
What are 2 types of antimicrobial drug actions?
1. Cidal agents: kill microbes 2. Static agents: inhibit the growth of microbes
78
What are the 5 classes of antimicrobial drugs?
1. inhibitors of bacterial cell wall synthesis 2. pr synthesis inhibitors 3. metabolic antagonists 4. NA synthesis inhibition 5. cell membrane disruption
79
What is the key structural feature of penicillin's for their bioactivity?
The β-lactam ring is the crucial structural feature of penicillin's required for their bioactivity.
80
What are penicillins?
inhibitors of bacterial cell wall synthesis
81
How does penicillin prevent bacterial cell wall synthesis?
prevent cross-linking of peptidoglycan leading to osmotic cell lysis
82
What do penicillin-resistant organisms produce to counteract penicillin?
Penicillin-resistant organisms produce β-lactamase (also known as penicillinase), an enzyme that breaks down the β-lactam ring and inactivates penicillin.
83
What step in bacterial cell wall synthesis do penicillins inhibit?
Penicillins inhibit the last step in bacterial cell wall synthesis, known as transpeptidation, which is crucial for forming the cell wall.
84
Why does penicillin only act on growing bacteria?
because it targets the synthesis of new peptidoglycan, a process that occurs during bacterial growth.
85
How do many antibiotics inhibit protein synthesis in prokaryotes?
Many antibiotics bind to the prokaryotic ribosome, not eukaryotic ribosomes, thereby inhibiting protein synthesis. They have a relatively high therapeutic index.
86
What is one way protein synthesis inhibitors kill bacteria?
Some antibiotics cause mistranslated proteins to be inserted into the plasma membrane, which triggers a stress response, leading to the creation of hydroxyl radicals that kill the bacteria. This is most effective against Gram-negative bacteria.
87
What steps in protein synthesis do some inhibitors block?
- Transfer RNA binding - Peptide bond formation - mRNA reading - Translocation
88
What are Aminoglycoside antibiotics, and what do they target?
Aminoglycoside antibiotics are protein synthesis inhibitors with a cyclohexane ring and amino sugars. They bind to the 30S ribosomal subunit to block protein synthesis.
89
What is a potential downside of Aminoglycoside antibiotics?
Aminoglycoside antibiotics can have toxic effects, especially with prolonged use.
90
What are six mechanisms by which bacteria develop drug resistance?
1. Alteration of target enzyme or organelle. 2. Inactivation of drug by degradation. 3. Inactivation of drug by modification. 4. Pump the drug out (efflux pumps). 5. Prevent entry of the drug into the cell. 6. Use alternate pathways or increase production of the target metabolite.
91
How does drug resistance arise in bacteria?
- Spontaneous mutations in bacterial chromosomes (rare). - Acquisition of Resistance (R) plasmids through conjugation, transduction, or transformation, which can carry multiple resistance genes.
92
How are resistance genes transferred between bacteria?
transferred through conjugation, transduction, and transformation
93
What are R plasmids?
R plasmids are resistance plasmids that can carry multiple resistance genes and are transferred between bacteria, contributing to the spread of antibiotic resistance.
94
What are Biological Safety Cabinets?
- enclosed, ventilated laboratory workspaces designed to provide protection for the user, the environment, and the materials being handled - uses laminar airflow and HEPA filtration to sterilize
95
What are autoclaves?
- devices used to sterilize equipment, instruments and other materials by using high pressure saturated steam at elevated temperatures - they work by applying heat and pressure to kill all microorganisms

CBE 2290 (12 decks)

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