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Intro Biology > Microbial Control > Flashcards

Microbial Control Flashcards

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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
Q

Why is nitrite used in meat products?

A

Prevents endospore formation

26
Q

What are the Biosafety Levels?

A

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
Q

How should bleach be used in disinfection?

A

A 10% solution to kill vegetative bacteria and other microbes (no endospores).

28
Q

What was silver nitrite used for?

A

To treat gonorrhea (no longer)

29
Q

What are the three microbial control methods?

A

Physical, Chemical, and Mechanical

30
Q

What are the physical agents used in microbial control?

A

Heat and Radiation

31
Q

Types of Heat

A

Dry - Incineration (Sterilization)
Dry Oven - (Sterilization)

Moist - Steam under pressure (Sterilization)
Boiling Water, Hot Water, Pasteurization ((Disinfection)

32
Q

Types of Radiation

A

Ionizing - Gamma, X-Ray, Cathode (Sterilization)

Non-Ionizing - UV (Disinfection)

33
Q

Types of Chemical Agents

A

Gases (Sterilization, Disinfection)

Liquids (Animate) - Antisepsis

Inanimate - Disinfection, Sterilzation

34
Q

Mechanical microbial removal methods

A

Filtration (Air) - Disinfection

Filtration (Liquids) - Sterilization

35
Q

Static agents

A

Inhibit Microbe Growth

Eg: bacteriostatic, fungistatic

36
Q

-cidal agents

A

Destroy or kill microbes

Eg; bactericidal, fungicidal

37
Q

Sterilization

A

Complete removal or destruction of all viable microbes including endospores

38
Q

Decontamination

A

Use of physical or chemical methods to kill vegetative bacterial and other microbes except endospores

39
Q

Disinfectant

A

chemical agent used to kill vegetative forms of bacteria and other microbes on non-living surfaces such as wiping off table tops.

40
Q

Antiseptic

A

chemical agent used to control microbes on living tissue such as surgical scrubbing of patients

41
Q

Sanitization

A

reduction of microbial counts to acceptable levels of public health standards.

Example: Sanitization of eating utensils in 	restaurants
42
Q

Degerming

A

Physical removal or reduction of microbes from a limited area.

Example: Washing of hands with germicidal soap.
43
Q

Factors affecting efficacy of control methods

A

Number of microbes
Target microbe characteristics
Environmental factors - temperature, pH, biofilms
Concentration and mode of action of agent
Organic matter - sputum, blood, feces

44
Q

Ideal antimicrobial control agent

A

Inexpensive
Fast-acting
Stable during storage
Capable of controlling microbial growth while being harmless to humans, animals, and objects

45
Q

Modes of action for antimicrobials

A

Damage to cell wall
Alteration of membrane function
Damage to proteins
Damage to nucleic acids

46
Q

Damage to cell wall

A

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
Q

Injury to cell membrane

A

Bind and penetrate membrane lipids
Loss of selective permeability resulting in leakage of cytoplasmic contents.

Ex: Surfactants – surface active agents.
48
Q

Effects on Nucleic Acids

A

Irreversible binding to microbial DNA results in:
Ceasation of transcription and translation
Fatal mutations

Ex: Formaldehyde and ionizing radiation
49
Q

Effects on proteins

A

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
Q

Boiling

A

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
Q

Pasteurization

A

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
Q

Pasteurization Methods

A

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
Q

Autoclaving

A

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
Q

Dry Heat

A

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
Q

Hot air oven

A

Effective at 170˚C for 2 hrs

Useful for sterilization of glasswares and oils

56
Q

Incineration

A

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
Q

Ionizing radiation

A

Ejects orbital electrons from an atom to create ions
Ions create radicals and denature DNA

High energy - penetrates liquids and solids effectively.

58
Q

Nonionizing radiation

A

Raises atoms to a higher energy level
Low energy - less penetrating
UV - formation of pyrimidine dimers

59
Q

Applications of ionizing radiation

A

Alternative sterilization method
Materials sensitive to heat or chemicals
Some foods (fruits, vegetables, meats)

60
Q

Applications of Nonionizing radiation

A

Alternative disinfectant

Germicidal lamp in hospitals, schools, food preparation areas (inanimate objects, air, water)

Intro Biology (9 decks)

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