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Intro Biology > Microbial Control > Flashcards

Microbial Control Flashcards

(60 cards)

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1
Q

How is osmotic pressure used to inhibit growth?

A

High concentrations of salt or sugar in foods to inhibit growth

Cells in hypertonic solution of salt or sugar lose water = plasmolysis

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2
Q

Which have a greater ability to survive hypertonic environments? Bacteria or Fungi?

A

Fungi

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3
Q

What radiation is an alternative to chlorine gas treatment?

A

UV Radiation

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4
Q

What is more penetrating? Gamma or UV radiation?

A

Gamma radiation

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5
Q

Which form of radiation is sterilizing? UV or Gamma radiation?

A

Both are sterilizing

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6
Q

How do you know if food has been gamma irradiated

A

The radora logo.

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7
Q

What control method uses membranes to remove spores and microbes from the air?

A

Filtration

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8
Q

When is filtration used?

A

Liquids that are sensitive to heat (e.g. serum, vaccines, media)

HEPA filtration of operating rooms etc.

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9
Q

What does HEPA stand for?

A

High Efficiency Particulate Air

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10
Q

Does cold kill microbes?

A

No. It only reduced their metabolic activity.

Except for psychrophiles.

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11
Q

Stopping microbial metabolism by dehydration.

A

dessication

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12
Q

Preserving microbes and vaccines by freeze drying.

A

Lyophilization

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13
Q

Phenol and Phenolics

Examples and uses

A

Phenol - carbolic acid

  • Used by Joseph Lister
  • Has bad smell

Phenolic - Lysol

Disrupt plasma membranes

Used in cutting boards, kitty litter

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14
Q

Biguanides

Example and use

A

Surgical hand scrubs and preoperative skin preparation

disrupt plasma membranes

Ex: Chlorhexidine

  • replaced carbolic acid
  • No smell
  • No skin irritation
  • stays on the skin longer
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15
Q

Halogens

A

Oxidizing agents

Disrupt sulfhydryl groups in amino acids

Iodine

Chlorine

Tincture + Iodine (both antiseptic)

  • Idophor - Iodine + proprietary organic base
    Organic base allows iodine to stay on longer
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16
Q

Alcohols

A

Dissolve membrane lipids, denatures proteins.

Used for skin degerming.

Ethanol, Isopropanol

70% concentration - most effective

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17
Q

Soaps and detergents

A

Quaternary ammonium (quats):

Cationic
Denature proteins and disrupt cell membrane
Low-level disinfectant in the clinical setting

Soaps and detergents:
Fatty acids, oils, sodium or potassium salts
Sanitizing and degerming agents
More effective if mixed with germicides

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18
Q

Heavy Metals

A

Ag (Silver), Hg (Mercury), Cu (Copper)

Denature proteins
Oligodynamic action
Preservatives in cosmetics and ophthalmic solutions.
Silver nitrate - Ophthalmia neonatorum prophylaxis.
Silver sulfadiazine - burn patients and catheter tips.

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19
Q

Aldehydes

A

Formaldehyde, Glutaraldehyde

Sterilants for surgical and dialysis instruments

Also formaldehyde is an embalming fluid

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20
Q

Gases

A

Denature proteins and affect functional groups of DNA.

Sterilizes plastic materials
Example: Ethylene oxide

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21
Q

Peroxygens

A

Oxidizing agents - form hydroxyl free radicals
Effective against anaerobes

Examples:
H2O2 (Hydrogen Peroxide) - skin and wound cleaner
Peracetic acid - quick method for sterilizing medical equipment
O3 (Ozone) - water treatment

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22
Q

Enzymes

A

Antimicrobial enzymes act against microorganisms
Human tears contain lysozyme
Digests peptidoglycan cell wall of bacteria

Uses of enzymes to control microbes in the environment
Lysozyme is used to reduce the number of bacteria in cheese
Prionzyme can remove prions on medical instruments

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23
Q

Prionzyme

A

Enzyme used to remove prions on medical instruments

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24
Q

Food preservatives

A

Inhibits metabolism
Control molds and bacteria in food and cosmetics

Examples:
Organic acids - sorbic, benzoic, acetic acids
Calcium propionate - bread
Nitrite prevents endospore formation in meat products.

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25
Why is nitrite used in meat products?
Prevents endospore formation
26
What are the Biosafety Levels?
Four levels of safety in labs dealing with pathogens Biosafety Level 1 (BSL-1)- Handling microbes that do not cause disease in humans Biosafety Level 2 (BSL-2)- Handling moderately hazardous agents Biosafety Level 3 (BSL-3)- All manipulations of microbes done in safety cabinets Biosafety Level 4 (BSL-4)- Handling microbes that cause severe or fatal disease; Lab space is isolated, and personnel wear protective suits
27
How should bleach be used in disinfection?
A 10% solution to kill vegetative bacteria and other microbes (no endospores).
28
What was silver nitrite used for?
To treat gonorrhea (no longer)
29
What are the three microbial control methods?
Physical, Chemical, and Mechanical
30
What are the physical agents used in microbial control?
Heat and Radiation
31
Types of Heat
Dry - Incineration (Sterilization) Dry Oven - (Sterilization) Moist - Steam under pressure (Sterilization) Boiling Water, Hot Water, Pasteurization ((Disinfection)
32
Types of Radiation
Ionizing - Gamma, X-Ray, Cathode (Sterilization) Non-Ionizing - UV (Disinfection)
33
Types of Chemical Agents
Gases (Sterilization, Disinfection) Liquids (Animate) - Antisepsis Inanimate - Disinfection, Sterilzation
34
Mechanical microbial removal methods
Filtration (Air) - Disinfection Filtration (Liquids) - Sterilization
35
Static agents
Inhibit Microbe Growth Eg: bacteriostatic, fungistatic
36
-cidal agents
Destroy or kill microbes Eg; bactericidal, fungicidal
37
Sterilization
Complete removal or destruction of all viable microbes including endospores
38
Decontamination
Use of physical or chemical methods to kill vegetative bacterial and other microbes except endospores
39
Disinfectant
chemical agent used to kill vegetative forms of bacteria and other microbes on non-living surfaces such as wiping off table tops.
40
Antiseptic
chemical agent used to control microbes on living tissue such as surgical scrubbing of patients
41
Sanitization
reduction of microbial counts to acceptable levels of public health standards. Example: Sanitization of eating utensils in restaurants
42
Degerming
Physical removal or reduction of microbes from a limited area. Example: Washing of hands with germicidal soap.
43
Factors affecting efficacy of control methods
Number of microbes Target microbe characteristics Environmental factors - temperature, pH, biofilms Concentration and mode of action of agent Organic matter - sputum, blood, feces
44
Ideal antimicrobial control agent
Inexpensive Fast-acting Stable during storage Capable of controlling microbial growth while being harmless to humans, animals, and objects
45
Modes of action for antimicrobials
Damage to cell wall Alteration of membrane function Damage to proteins Damage to nucleic acids
46
Damage to cell wall
Blockage of cell wall synthesis Degradation of cell wall components Reduction of its stability and integrity When damaged, effects of osmosis cause cells to burst Ex: Penicillin, detergents, alcohols
47
Injury to cell membrane
Bind and penetrate membrane lipids Loss of selective permeability resulting in leakage of cytoplasmic contents. Ex: Surfactants – surface active agents.
48
Effects on Nucleic Acids
Irreversible binding to microbial DNA results in: Ceasation of transcription and translation Fatal mutations Ex: Formaldehyde and ionizing radiation
49
Effects on proteins
Blockage of enzyme active sites prevents binding of substrate. Protein denaturation Protein function depends on 3-D shape Example: Heat, acids, alcohols, phenolics, and metallic ions.
50
Boiling
Boiling at 100 ˚C for 10-30 minutes kills most non- spore forming pathogens. Ex: Boiling of baby bottles and unsafe drinking water Hepatitis B virus needs at least 1 hour of boiling to be killed.
51
Pasteurization
Pasteurization reduces spoilage caused by microbes and kills pathogens. Thermoduric microbes survive Used in milk industry, wineries, breweries. Prevents transmission of milk-borne diseases caused by: Salmonella, Campylobacter, Listeria, Mycobacteria.
52
Pasteurization Methods
Classical (Batch): 63 ˚C for 30 minutes High Temperature Short Time (Flash): 72 ˚C for 15 seconds Ultra High Temperature: 140 ˚C for < 1 second
53
Autoclaving
Uses steam under pressure Used in media preparation and glassware sterilization Autoclave setting at 121 ˚C, 15 p.s.i. pressure for at least 15 minutes effectively destroys spores. Pressure cooker – a table top autoclave.
54
Dry Heat
Used for materials that cannot be sterilized with moist heat Denatures proteins and oxidizes metabolic and structural chemicals Requires higher temperatures for longer time than moist heat Incineration is ultimate means of sterilization
55
Hot air oven
Effective at 170˚C for 2 hrs | Useful for sterilization of glasswares and oils
56
Incineration
destroys microbes to ashes or gas Bunsen flame - up to 1870˚C Ex: Sterilization of loops and needles. Furnace - 800˚C to 6500˚C Ex: Incineration of animal carcasses.
57
Ionizing radiation
Ejects orbital electrons from an atom to create ions Ions create radicals and denature DNA High energy - penetrates liquids and solids effectively.
58
Nonionizing radiation
Raises atoms to a higher energy level Low energy - less penetrating UV - formation of pyrimidine dimers
59
Applications of ionizing radiation
Alternative sterilization method Materials sensitive to heat or chemicals Some foods (fruits, vegetables, meats)
60
Applications of Nonionizing radiation
Alternative disinfectant Germicidal lamp in hospitals, schools, food preparation areas (inanimate objects, air, water)

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