Podcast
Questions and Answers
At what temperature does an autoclave sterilize microbiological media and lab equipment?
At what temperature does an autoclave sterilize microbiological media and lab equipment?
Which method utilizes rapid freezing under vacuum for preservation?
Which method utilizes rapid freezing under vacuum for preservation?
What is the primary function of high-efficiency particulate air (HEPA) filters?
What is the primary function of high-efficiency particulate air (HEPA) filters?
What is one characteristic of a good disinfectant or antiseptic?
What is one characteristic of a good disinfectant or antiseptic?
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Which type of radiation alters molecular structures and can sterilize food items?
Which type of radiation alters molecular structures and can sterilize food items?
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What does the phenol coefficient measure?
What does the phenol coefficient measure?
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What is the main use of filtration in microbial control?
What is the main use of filtration in microbial control?
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Which of the following methods is NOT a way to evaluate the effectiveness of disinfectants?
Which of the following methods is NOT a way to evaluate the effectiveness of disinfectants?
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What is the effect of cold storage on microorganisms?
What is the effect of cold storage on microorganisms?
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What class of chemical antimicrobial agents does formaldehyde belong to?
What class of chemical antimicrobial agents does formaldehyde belong to?
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Which organisms exhibit the highest level of resistance to microbial control methods?
Which organisms exhibit the highest level of resistance to microbial control methods?
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What is the definition of sterilization in microbial control?
What is the definition of sterilization in microbial control?
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Which term describes the steps taken to prevent contamination of sterile surfaces?
Which term describes the steps taken to prevent contamination of sterile surfaces?
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What does a 'cide' suffix indicate in terms of microbial control?
What does a 'cide' suffix indicate in terms of microbial control?
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How is 'decimal reduction time' (D-value) best defined?
How is 'decimal reduction time' (D-value) best defined?
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Which method of microbial control is characterized by burning organisms to ashes?
Which method of microbial control is characterized by burning organisms to ashes?
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Which type of microbial structure is considered to have moderate resistance to control methods?
Which type of microbial structure is considered to have moderate resistance to control methods?
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What does the thermal death point indicate?
What does the thermal death point indicate?
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Degerming involves which of the following actions?
Degerming involves which of the following actions?
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What does the microbial death curve illustrate?
What does the microbial death curve illustrate?
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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
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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.
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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).
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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).
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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
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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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Description
Test your knowledge on various microbial control methods including the types of resistance and key terms such as sterilization, disinfection, and aseptic techniques. This quiz covers essential concepts to understand how to manage and eliminate harmful microbes effectively.
