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Microbiology > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

Controlling microorganisms

A
  • controlling our degree of exposure to potentially harmful microbes is a monumental concern in our lives
  • the methods of microbial control used outside of the body are designed to result in four possible outcomes:
    • sterilization
    • disinfection
    • decontamination (also called sanitization)
    • antisepsis (also called degermination)
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2
Q

How to control microbes

A

Cleaning: scrubbing, bleach (and Clorox), steaming, Lysol, hydrogen peroxide (H2O2), soap (dawn dish soap), Mr. Clean, heat

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3
Q

Sterilization

A
  • Process that destroys or removes all viable microorganisms (including viruses)
  • the complete removal or destruction of all viable microorganisms. Used on inanimate objects
    Key points: The term sterile should be used only in the strictest sense to refer to materials that have been subjected to the process of sterilization (there is no such thing as slightly sterile) Generally reserved for inanimate objects as it would be impractical or dangerous to sterilize parts of the human body
    Common uses: surgical instruments, syringes, commercially packaged food
    Examples of agents: Heat (autoclave), sterilants (chemical agents capable of destroying endospores)
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4
Q

Disinfection

A
  • Physical process or a chemical agent to destroy vegetative pathogens but not bacterial endo spores. It removes harmful products of microorganisms (toxins) from material
  • the destruction or removal of vegetative pathogens but not bacterial endospores. Usually only used on inanimate objects
    Key points: Normally used on inanimate objects because the concentration of disinfectants required to be effective is harmful to human tissue Common uses: boiling food utensils, applying 5% bleach solution to an examining table, immersing thermometers in an iodine solution between uses
    Examples of agents: bleach, iodine, heat (boiling)
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5
Q

Decontamination/sanitization

A
  • Cleansing technique that mechanical removes microorganisms as well as other debris to reduce contamination to safe levels
  • the mechanical removal of most microbes
    Key points: Important to restaurants, dairies, breweries, and other commercial entities that handle large numbers of soiled utensils/containers Common uses: Cooking utensils, dishes, bottles, and cans must be sanitized for reuse
    Examples of agents: soaps, detergents, commercial dishwashers
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6
Q

Antisepsis/degermination

A
  • reduces the number of microbes on the human skin. Is a form of decontamination but is on living tissues
  • chemicals applied to body surfaces to destroy or inhibit vegetative pathogens
    Key points: involves scrubbing the skin (mechanical friction) or immersing it in chemicals (or both)
    Examples of agents: alcohol, surgical hand scrubs
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7
Q

When controlling microbes: what do you need to consider?

A
  • What surface you are cleaning
  • What time it needs to sit for
  • the cost of the materials
  • the item you are using
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8
Q

Relative resistance of microbial forms

A
  • primary targets of microbial control are microorganisms capable of causing infection or spoilage in the environment or on the human body
    - the targeted population often contains mixtures of microbes with extreme differences in resistance and harmfulness
    - bacterial endospores have traditionally been considered the most resistant microbial entities
    The goal of sterilization process is the destruction of bacterial endospores: any process that kills endospores will invariably kill all less resistant microbial forms
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9
Q

Examples of mechanical removal methods

A
  • filtration -> air -> liquids
    Decontamination
    Sterilization
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10
Q

Examples of disinfection, sterilization, antisepsis/degermation, decontamination/sanitization

A

Disinfection -> bleach, iodine, heat (boiling)
Sterilization -> heat (autoclave), sterilants (chemical agents)
Decontamination/sanitization -> soaps, detergents, commercial dishwashers
Antisepsis/degermation -> alcohol, surgical hand scrubs

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11
Q

Agents versus processes

A
  • sterilization and disinfection: processes
    • agents used in the process:
      • Bactericide: chemical that destroys bacteria except for those in the endospores stage
      • fungicide: chemical that can kill fungal spores, hyphae, yeasts
      • virucide: chemical known to inactivate viruses, especially on living tissues
      • sporicide: an agent capable of destroying bacterial endospores
      • germicide/microbicide: chemical agents that kill microorganisms
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12
Q

Agents versus processes: sepsis versus asepsis

A

Sepsis: the growth or microorganisms in the blood and other tissues
Asepsis: any practice that prevent the entry of infectious agents into sterile tissues and thus prevents infection
- aseptic techniques: practiced in health care; range from sterile methods to antisepsis

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13
Q

Agents versus processes: antiseptics

A

Antiseptics: chemical agents applied directly to exposed body surfaces (skin and mucous membranes), wounds, and surgical incision to prevent vegetative pathogens
- preparing the skin before surgical incisions with iodine compounds
- swabbing an open root canal with hydrogen peroxide
- ordinary hand washing with a germicidal soap

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14
Q

Agents versus processes: status and static

A
  • statis and static mean “to stand still”
  • bacteristatic: chemical agents that prevent the growth of bacteria on tissues or on objects in the environment
  • fungistatic: chemicals that inhibit fungal growth
  • antiseptics and drugs often have microbistatic effects because microbial compounds can be toxic to human cells
  • even a -cidal agent does not necessarily result in sterilization, depending on how it is used
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15
Q

Other considerations in microbial control

A

Substances that require sterilization:
- durable solids (rubber) to sensitive liquids (serum)
- situations requiring sterilizations confront persons involved in healthcare
- no universal methods work well in every case
Considerations of sterilization: cost, effectiveness, method of disposal

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16
Q

What is microbial death?

A
  • death: permanent termination of an organism’s vital processes
  • microbes have no conspicuous vital processes; therefore, death is difficult to determine
  • permanent loss or reproductive capability, even under optimum growth conditions, has become the accepted microbiological definition of death
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17
Q

Factors that affect death rate

A

Death of the whole population is not instantaneous:
• Begins when a certain threshold of microbicidal agent is met
• Death continues in a logarithmic manner as the time or concentration is increased
• Active cells tend to die more quickly than less metabolically active cells
• Eventually, a point is reached at which survival of any cells is highly unlikely; this point is equivalent to sterilization

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18
Q

Factors that influence the action of anti microbial agents

A

The number of microbes:
• Higher load of contaminants takes longer to destroy
The nature of the microorganisms in the population:
• Target population is usually a mixture of bacteria, fungi, spores, and viruses with broad spectrum of resistance
Temperature and pH of the environment

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19
Q

Factors that influence the action of anti microbial agents (2)

A

The concentration (dose, intensity) of the agent:
- UV radiation is most effective at 260nm
- most disinfectants are more active at higher concentrations

The mode of action of the agent:
- How does it kill of inhibit the microorganisms?

The presence of solvents, interfering organic matter, and inhibitors:
- saliva, blood, and feces can inhibit the actions of disinfectants and even of heat

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20
Q

Actions of values physical and chemical agents upon the cell
- cell wall

A

Chemical agents can damage the cell wall by:
- blocking its synthesis
- digesting it
Examples of agents used:
- chemicals
- detergents
- alcohol

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21
Q

Actions of various physical and chemical agents upon the cell wall
- cytoplasmic membrane

A
  • Agents disrupt the lipid layer of the cytoplasmic membrane. This opens up the cytoplasmic membrane and allows damaging chemicals to enter the cell and important ions to exit the cell.
  • examples of agents used: detergents, alcohol
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22
Q

Actions of various physical and chemical agents upon the cell
- cellular synthesis

A
  • Agents can interrupt the synthesis of proteins via the ribosomes, inhibiting proteins needed for growth and metabolism and preventing multiplication.
    Agents can change genetic codes (mutation).
  • examples of agents used: formaldehyde, radiation, ethylene oxide
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23
Q

Actions of various physical and chemical agent upon the cell
- proteins

A
  • Some agents are capable of denaturing proteins (breaking of protein bonds, which results in breakdown of the protein structure).
    Agents may attach to the active site of a protein, preventing it from interacting with its chemical substrate
  • examples of agents used: moist heat, alcohol, phenolics
24
Q

Methods of physical control: heat

A
  • elevated temperatures are microbicidal (death)
  • lower temperatures are microbistatic (staying)
  • moist heat: hot water, boiling water, or steam between 60 - 135 degrees Celsius
  • dry heat: hot air or an open flam, which ranges from 160 to several thousand degrees Celsius
25
Q

Mode of action and relative effectiveness of moist heat

A

Moist heat:
- operates at lower temperatures and shorter exposure times to achieve the same effectiveness as dry heat
- microbicidal effect is the coagulation and desaturation of proteins

26
Q

Mode of action and relative effectiveness of Dry Heat

A

Dry heat:
- dehydrates the cell, removing water necessary for metabolic reactions
- denatures proteins
- increases the stability of some protein conformations, requiring higher temperatures
- at very high temperatures, oxidizes cells, burning them to ashes

27
Q

Heat resistance and thermal death: Endospores and vegetative cells

A

Bacterial endospores:
- exhibit greatest resistance
- destruction of spores required temperatures above boiling

Vegetative cells:
- vary in sensitivity to heat
- death times vary from 50 degrees C for 3 minutes to 60 degrees C for 60 minutes

28
Q

Moist heat methods:
- boiling water:disinfection

A

• A simple boiling water bath can quickly decontaminate items in the clinic and home.
• Because a single processing at 100°C will not kill all resistant cells, this method can be relied on only for disinfection and not for sterilization.
• Exposing materials to boiling water for 30 minutes will kill most non-endospore-forming pathogens, including resistant species such as the tubercle bacillus and staphylococci.
• Probably the greatest disadvantage with this method is that the items can be easily recontaminated when removed from the water.

29
Q

Moist heat methods:
- disinfection of beverages

A

• Fresh beverages such as milk, fruit juices, beer, and wine are easily contaminated during collection and processing.
• Because microbes have the potential for spoiling these foods or causing illness, heat is frequently used to reduce the microbial load and destroy pathogens.
• Pasteurization is a technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid’s flavor and nutritional value.

30
Q

Define pasteurization

A
  • a technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid’s flavor and nutritional value
31
Q

Moist heat methods:
- steam under pressure autoclaving

A

• Heat-resistant materials such as glassware, cloth (surgical dressings), metallic instruments, liquids, paper, some media, and some heat-resistant plastics. If items are heat-sensitive (plastic Petri dishes) but will be discarded, the autoclave is still a good choice. However, it is ineffective for sterilizing substances that repel moisture (oils, waxes), or for those that are harmed by it (powders).
• Steam Under Pressure: At sea level, normal atmospheric pressure is 15 pounds per square inch (psi), or 1 atmosphere. At this pressure, water will boil (change from a liquid to a gas) at 100°C, and the resultant steam will remain at exactly that temperature, which is unfortunately too low to reliably kill all microbes. In order to raise the temperature of steam, the pressure at which it is generated must be increased. As the pressure is increased, the temperature at which water boils and the temperature of the steam produced both rise. For example, at a pressure of 20 psi (5 psi above normal), the temperature of steam is 109°C. As the pressure is increased to 10 psi above normal, the steam’s temperature rises to 115°C, and at 15 psi above normal (a total of 2 atmospheres), it will be 121°C. It is not the pressure by itself that is killing microbes but the increased temperature it produces.

32
Q

Dry heat methods:
- incineration

A

• A flame is perhaps the most rigorous of all heat treatments.
• The flame of a Bunsen burner reaches 1,870°C at its hottest point, and furnaces/incinerators operate at temperatures of 800°C to 6,500°C.
• Direct exposure to such intense heat ignites and reduces microbes and other substances to ashes and gas.

33
Q

Dry heat methods:
- hot air oven

A

• The hot-air oven provides another means of dry-heat sterilization. The so-called dry oven is usually electric (occasionally gas) and has coils that radiate heat within an enclosed compartment.
• Heated, circulated air transfers its heat to the materials in the oven.
• Sterilization requires exposure to 150°C to 180°C for 2 to 4 hours, which ensures thorough heating of the objects and destruction of endospores.

34
Q

The effects of desiccation

A
  • vegetative cells directly exposed to normal room temperature gradually becoming dehydrated
  • some microbes are killed by desiccation; many others are not killed and some are even preserved
35
Q

The effects of lyophilization

A
  • combination of freezing and drying
  • method of preserving microorganisms in a viable state for many years
  • pure cultures are frozen instantaneously and exposed to a vacuum that removes water, avoiding formation of ice crystals
36
Q

Radiation

A
  • energy emitted from atomic activities and dispersed at high velocity through matter or space:
    - gamma rays
    - X rays
    - ultraviolet radiation
37
Q

Radiation methods
- Ionizing radiation: gamma rays and X rays

A

• Ionizing radiation is a highly effective alternative for sterilizing materials that are sensitive to heat or chemicals.
• Devices that emit ionizing rays include gamma-ray machines containing radioactive cobalt, X-ray machines similar to those used in medical diagnosis, and cathode-ray machines.
• Items are placed in these machines and irradiated for a short time with a carefully chosen dosage

38
Q

Radiation methods
- non ionizing radiation: ultraviolet rays

A

• Ultraviolet (UV) radiation ranges in wavelength from approximately 100 to 400 nm.
• It is most lethal from 240 to 280 nm (with a peak at 260 nm).
• Owing to its lower energy state, UV radiation is not as penetrating as ionizing radiation. Because UV radiation passes readily through air, slightly through liquids, and only poorly through solids, the object to be disinfected must be directly exposed to it for full effect.

39
Q

Filtration

A

Effective method to remove microbes from the air and liquids:

• Fluid is strained through a filter with openings large enough for the fluid to pass, but too small for microbes
• Also used are thin membranes of cellulose acetate, polycarbonate, and plastics whose pore size is carefully controlled
• Charcoal, diatomaceous earth, or unglazed porcelain are also used
• Pore sizes can be controlled to permit true sterilization by trapping viruses or large proteins

40
Q

Osmotic pressure

A
  • adding large amounts of salt or sugar to food creates a hypertonic environment for bacteria, causing plasmolysis
  • pickling, smoking, and drying foods have been used for centuries to preserve foods
  • osmotic pressure is never a sterilizing technique (they need water for all preservation methods; limit bacteria growth but do not sterilize)
41
Q

Methods of chemical control

A
  • occurs in the liquid, gaseous, or solid state
  • range from disinfectants and antiseptics to sterilants and preservatives
    Aqueous: chemicals dissolved in pure water as the solvents
    Tinctures: chemicals dissolved in pure alcohol or alcohol-water mixtures
42
Q

Boiling point of Celsius

A

100 degrees Celsius of 212 degrees Fahrenheit
- when hiking boil water for at least 30 minutes

43
Q

Desirable qualities in a germicide

A

• Rapid action, even in low concentrations
• Solubility in water or alcohol and long-term stability
• Broad-spectrum microbicidal action without being toxic to human and animal tissues
• Penetration of inanimate surfaces to sustain a cumulative or persistent action
• Resistance to becoming inactivated by organic matter
• Not corrosive and nonstaining
• Sanitizing and deodorizing properties
• Affordability and availability

44
Q

High-, intermediate-, and low-level germicides

A

Germicides are evaluated in terms of their effectiveness in destroying microbes in medical and dental settings:
• High-level germicides kill endospores and can be used as sterilants
• Intermediate-level germicides kill fungal, but not bacterial, spores, resistant pathogens, and viruses (Lysol spray is an intermediate-level or low level germicide. We don’t know if it kills spores or vegetative fungal cells)
• Low-level germicides eliminate only vegetative bacteria, vegetative fungal cells, and some viruses

45
Q

Factors affecting the germicidal activity of chemicals

A
  • nature of the microorganisms being treated
  • nature of the material being treated
  • degree of contamination
  • time of exposure
  • strength and chemical action of the germicide
46
Q

Chemical methods of microbial control:
Phenol and phenolics

A
  • denature proteins and disrupt cell membranes
  • effective in presence of organic matter
  • remain active for a prolonged time
  • commonly used in the health care settings, labs, and homes
  • have disagreeable odor and possible side effects
47
Q

Chemical methods or microbial control: alcohols

A
  • intermediate-level disinfectants
  • denature proteins and disrupt cytoplasmic membranes
  • more effective than soap in removing bacteria from hands
  • swabbing of skin with alcohol prior to injection removes most microbes
  • not effective against fungal spores or bacterial endospores
48
Q

Heavy metals and their compounds

A

Oligodynamic action - very small amounts exert anti microbial activity
- denature proteins - Ag, Hg, Cu, Zn
- silver nitrate is used to prevent ophthalmia neonatorum
- mercuric chloride prevents mildew in paint
- copper sulfate is an algicide
- zinc chloride is found in mouthwash

49
Q

Chemical methods of microbial control
- halogens

A
  • intermediate-level antimicrobial chemicals
  • damage enzymes by desaturation
  • widely used in numerous applications
    • iodine tablets, iodophors, chlorine treatment, bleach, chloramphenicol, and bromine disinfection
50
Q

The disk-diffusion method

A
  • evaluates efficacy of chemical agents
  • filter paper disks are soaked in a chemical and placed in a culture
  • look for zone of inhibition around disks
  • qualitative test (yes or no, check marks) in chapter 9. Quantitative test (get a ruler and measure it) in chapter 10
51
Q

Chemical strength or concentration

A
  • dilutions: a small volume of the liquid chemical is diluted in a larger volume of solvent to achieve a certain ratio
  • parts per million: used for solutions such as chlorine that are effective in very diluted concentrations
  • percentage solutions: solute is added to water by weight or volume
52
Q

Other factors affecting the germicidal activity of chemicals

A

Length of exposure:
- most compounds require adequate contact time to allow the chemical to penetrate and act on microbes present

Composition of material being treated:
- smooth, solid objects are more reliably disinfected than those with pores or pockets that can trap soil
- large amounts of organic material can hinder penetration
- adequate cleaning of instruments and other reusable material must precede the use of a germicide or sterilant

53
Q

Filtration

A
  • filtration is a process of separating or straining
54
Q

Disk-diffusion method steps

A
  • the zone of inhibition -> when there is no growth and there is a nice clearing around it
  • you give a plus or a negative - meaning that there is no growth. +clearing around it ++ large clearing around it
55
Q

Qualitative and quantitative

A

Qualitative - a yes or no
Quantitative - a measurement (get a ruler, know to actually measure it)

Microbiology (23 decks)

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