Unit 3.Section 1. Chapter 13

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Questions and Answers

At what temperature does an autoclave sterilize microbiological media and lab equipment?

  • 170 degrees Celsius
  • 121 degrees Celsius (correct)
  • 100 degrees Celsius
  • 265 degrees Celsius

Which method utilizes rapid freezing under vacuum for preservation?

  • Desiccation
  • Lyophilization (correct)
  • Pasteurization
  • Refrigeration

What is the primary function of high-efficiency particulate air (HEPA) filters?

  • Trapping particles and microorganisms (correct)
  • UV radiation exposure
  • Sterilization of liquids
  • Increasing air temperature

What is one characteristic of a good disinfectant or antiseptic?

<p>Non-toxic to humans and animals (D)</p> Signup and view all the answers

Which type of radiation alters molecular structures and can sterilize food items?

<p>Ionizing radiation (D)</p> Signup and view all the answers

What does the phenol coefficient measure?

<p>The disinfecting ability relative to phenol (D)</p> Signup and view all the answers

What is the main use of filtration in microbial control?

<p>To remove microorganisms from solutions or gases (C)</p> Signup and view all the answers

Which of the following methods is NOT a way to evaluate the effectiveness of disinfectants?

<p>Microbial growth rate (A)</p> Signup and view all the answers

What is the effect of cold storage on microorganisms?

<p>Lowering their metabolic rate (B)</p> Signup and view all the answers

What class of chemical antimicrobial agents does formaldehyde belong to?

<p>Aldehydes (C)</p> Signup and view all the answers

Which organisms exhibit the highest level of resistance to microbial control methods?

<p>Bacterial endospores (B)</p> Signup and view all the answers

What is the definition of sterilization in microbial control?

<p>Complete removal of all living microbes on an object (B)</p> Signup and view all the answers

Which term describes the steps taken to prevent contamination of sterile surfaces?

<p>Aseptic technique (B)</p> Signup and view all the answers

What does a 'cide' suffix indicate in terms of microbial control?

<p>Causes microbial death (A)</p> Signup and view all the answers

How is 'decimal reduction time' (D-value) best defined?

<p>Time required to reduce bacterial population by 90% (D)</p> Signup and view all the answers

Which method of microbial control is characterized by burning organisms to ashes?

<p>Incineration (B)</p> Signup and view all the answers

Which type of microbial structure is considered to have moderate resistance to control methods?

<p>Bacteria (A)</p> Signup and view all the answers

What does the thermal death point indicate?

<p>Minimum temperature at which all organisms die within a specific time (B)</p> Signup and view all the answers

Degerming involves which of the following actions?

<p>Using mild chemicals and scrubbing on living tissue (B)</p> Signup and view all the answers

What does the microbial death curve illustrate?

<p>The effectiveness of various antimicrobial treatments over time (A)</p> Signup and view all the answers

Flashcards

Sterilization

The complete removal of all living microbes from an object or area.

Fomite

An object that transmits disease.

Disinfection

The process of killing or inhibiting the growth of pathogens on nonliving surfaces.

Asepsis

The process of killing or inhibiting the growth of pathogens on living tissue.

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Aseptic technique

A technique used to prevent contamination of sterile surfaces.

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Degerming

A protocol that reduces microbes using mild chemicals and scrubbing on living tissue.

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-cide

A suffix meaning "to kill" and indicates that a substance inactivates major enzymes of an organism, interfering with its metabolism.

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-static

A suffix that means "stay still" and indicates that a substance disrupts chemical reactions and slows metabolism.

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Microbial death

The permanent loss of reproductive capability of a microbe.

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Microbial death curve

A graphical representation of the progress of microbial control.

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Heat Sterilization

The process of using high heat to destroy microorganisms, typically used for sterilizing equipment, preparing lab media, and cooking food.

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Autoclave

A method of sterilization using high pressure steam at 121 degrees Celsius for 15 minutes, effective for killing even heat-resistant spores.

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Lyophilization (Freeze-Drying)

A method of preserving food by rapidly freezing it under a vacuum, which removes water and prevents ice crystal formation.

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Ionizing Radiation Sterilization

A method of sterilization using ionizing radiation, such as gamma rays, to alter the molecular structure of microorganisms.

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UV Radiation Sterilization

A method of sterilization using non-ionizing UV radiation, specifically at 265nm, which damages the DNA of microorganisms.

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Filtration

A physical method of removing microorganisms from solutions or gases by passing them through a filter with pores too small for them to pass.

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HEPA Filter

A type of filter with densely packed fibers that captures particles, organisms, and spores, commonly used in air purification systems.

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Membrane Filter

A type of filter made of cellulose fibers, used to separate microorganisms from liquids by trapping them on the filter pad.

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Antimicrobial Activity

The ability of a disinfectant or antiseptic to kill or inhibit the growth of microorganisms.

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Phenol Coefficient

A numerical value that compares the disinfecting power of a chemical to that of phenol, a standard disinfectant.

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Study Notes

Microbial Control Methods

  • Resistance to Control: Prions and bacterial endospores are the most resistant to microbial control. Bacteria, zygospores, and naked viruses have moderate resistance. Fungal spores, hyphae, and yeast are the least resistant.

Key Terms

  • Fomite: An object that transmits disease.
  • Sterilization: Complete removal of all living microbes.
  • Sanitization: Removal/reduction of microbes to safe levels.
  • Disinfection: Killing growth of pathogens on nonliving surfaces.
  • Asepsis: Killing growth of pathogens on living tissue.
  • Aseptic technique: Steps to prevent contamination of sterile surfaces.
  • Degerming: Reducing microbes using mild chemicals and scrubbing on living tissue.
  • -cide: To kill (inactivates major enzymes and interferes with metabolism).
  • -static: To stay still (disrupts chemical reactions and slows metabolism).
  • Microbial death: Permanent loss of reproductive capability.
  • Microbial death curve: Graphic representation of microbial control progress.
  • Decimal reduction time (D-value): Time for 90% death of a microbial population.
  • Thermal death time: Minimum time to kill entire population at a given temperature.
  • Incineration: Destroying by burning to ash.

Physical Control Methods

  • Heat: Oxidizes cellular components.
    • Boiling: 100°C at sea level for cooking, lab media prep, and personal use.
    • Dry-heat oven: 170°C for 2 hours to sterilize lab equipment.
    • Incineration: Destroys by direct flame.
    • Autoclave: 121°C for 15 minutes to sterilize heat-stable media and lab equipment.
    • Pasteurization: Prevents food spoilage using various temperatures.
  • Cold: Lowers metabolic rate of microorganisms.
    • Refrigeration: Short-term storage (0-7°C) of food and lab materials.
    • Freezing: Long-term storage of food and lab cultures (below 0°C).
  • Desiccation (Dehydration):
    • Simple desiccation: Drying (dried fruits, jerky).
    • Reducing water: Adding salt (salted meats, honey).
    • Lyophilization: Rapid freezing under vacuum (food preservation and lab cultures).
  • Radiation:
    • Ionizing radiation: Alters molecular structure (gamma rays) for sterilizing spices, medical items, and food.
    • Non-ionizing radiation: Causes mutations (UV rays) for sterilizing lab materials and water purification (265nm is germicidal).
  • Filtration: Removing microorganisms from solutions or gases.
    • High-efficiency particulate air (HEPA) filters: Trap particles, organisms, and spores.
    • Membrane filters: Cellulose pads for separating organisms from fluids.

Monitoring Autoclave Effectiveness

  • Autoclave tape darkens to indicate a successful run.

Filter Applications

  • Membrane filters: Separating organisms, viruses from cultures.
  • HEPA filters: Removing organisms from air/water samples.

Chemical Antimicrobial Agents

  • Phenolics: Denatures proteins and disrupts membranes (Lysol, antibacterial soaps).
  • Metals: Binds to proteins, inhibiting enzyme activity (wound treatment, mouthwash).
  • Halogens: Oxidation and destabilization of cellular macromolecules (bleach, medical hand scrub).
  • Alcohols: Denatures proteins and disrupts membranes (disinfectant, antiseptic).
  • Peroxides: Oxidation and cellular macromolecule destabilization.
    • Hydrogen peroxide - wound rinse
    • Benzoyl peroxide - teeth whitening, acne treatment
  • Aldehydes: Inactivation of viruses, toxins.
    • Formaldehyde
    • Glutaraldehyde
  • Detergents: Strong surfactants, attracted to phosphates.
  • Gases: Cold sterilization; good for various materials (ethylene oxide).

Disinfectant/Antiseptic Qualities

  • Kills/slows microbial growth.
  • Non-toxic to animals/humans.
  • Inexpensive.
  • Substantial shelf life.

Phenol Coefficient

  • Number comparing a disinfectant's/antiseptic's disinfecting ability to phenol.

Evaluating Disinfectant/Antiseptic Effectiveness

  • Phenol coefficient: Comparison to phenol's sterilizing ability.
  • Disk diffusion: Applying different chemicals to separate, sterile filter paper disks.
  • Dilution test: Cultures dried on cylinders exposed to chemical agents.
  • In-use test: Placing used, diluted disinfectant onto agar.

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