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Questions and Answers
Which of these methods involves the complete removal or destruction of all microorganisms?
Which of these methods involves the complete removal or destruction of all microorganisms?
Disinfection is a process to destroy only vegetative microbes, not endospores.
Disinfection is a process to destroy only vegetative microbes, not endospores.
True (A)
Which of the following is a disinfectant applied directly to body surfaces?
Which of the following is a disinfectant applied directly to body surfaces?
Which level of germicide can kill all pathogens, including bacterial endospores?
Which level of germicide can kill all pathogens, including bacterial endospores?
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The process of killing all viable microbes, including viruses and endospores, is referred to as ______.
The process of killing all viable microbes, including viruses and endospores, is referred to as ______.
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A fungicide kills bacteria.
A fungicide kills bacteria.
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What is the term used for the specific rate at which a microorganism dies off when treated with a killing agent?
What is the term used for the specific rate at which a microorganism dies off when treated with a killing agent?
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Which of the following factors DOES NOT affect the effectiveness of antimicrobial agents?
Which of the following factors DOES NOT affect the effectiveness of antimicrobial agents?
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Gram-positive bacteria are more susceptible to antimicrobial treatments than Gram-negative bacteria.
Gram-positive bacteria are more susceptible to antimicrobial treatments than Gram-negative bacteria.
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What is the term used for chemicals that are used internally to kill or inhibit the growth of microorganisms within host tissues?
What is the term used for chemicals that are used internally to kill or inhibit the growth of microorganisms within host tissues?
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What is the primary target of enveloped viruses for attachment to target cells?
What is the primary target of enveloped viruses for attachment to target cells?
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Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
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What two mechanisms of action do antimicrobial agents primarily rely on?
What two mechanisms of action do antimicrobial agents primarily rely on?
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Which of the following treatments is the most effective, as shown in the graph on antimicrobial treatments?
Which of the following treatments is the most effective, as shown in the graph on antimicrobial treatments?
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The death rate of bacterial populations when treated with a killing agent is always a constant rate, regardless of the speed of the killing process.
The death rate of bacterial populations when treated with a killing agent is always a constant rate, regardless of the speed of the killing process.
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What does 'D-value' stand for in microbial control?
What does 'D-value' stand for in microbial control?
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The D-value of 121, represented as D121, means that 90% of a microbial population is killed after 1 minute of exposure to 121°C.
The D-value of 121, represented as D121, means that 90% of a microbial population is killed after 1 minute of exposure to 121°C.
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Study Notes
Microbial Growth Control
- Microbial control methods can be physical or chemical
- Physical methods include heat, filtration, and radiation
- Chemical methods include disinfectants, germicides, and antibiotics
- When bacteria are treated with a killing agent, they usually die at a constant rate. This is called the death rate.
Microbial Control Methods: Terminology
- Sanitization: A mechanical/physical cleaning technique that removes microbes.
- Disinfection: A process that destroys vegetative microbes, but not endospores, usually on inanimate objects.
- Sterilization: A process that destroys all viable microbes, including viruses and endospores.
- Antisepsis: Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens.
- Chemotherapy: Chemicals used to kill or inhibit microorganisms within tissues.
Factors Affecting Effectiveness of Antimicrobial Agents
- Population Size: Larger populations require more time for killing.
- Species/Life Cycle: Different microbes have varying sensitivities to antimicrobial agents.
- Population Composition: Microbes differ distinctly in how they respond to antimicrobial treatments.
- Organic Matter: Presence of organic matter influences antimicrobial effectiveness.
- Environmental Factors (pH and Temperature): Antimicrobial effectiveness changes with environmental conditions.
- Mode of Action: Different antimicrobial methods have varied effects.
- Concentration/Dosage: Higher concentrations typically act faster.
- Duration of Exposure: Extended exposure usually results in more deaths.
Antimicrobial Agents: Action Mechanisms
- Alteration of Cell Walls/Cytoplasmic Membranes: Disrupts the structure and function of the cell.
- Interference with Proteins/Nucleic Acids: Interferes with protein and nucleic acid function.
- Damage to Proteins and Nucleic Acids: Chemicals, radiation, and heat affect 3-D protein shape and nucleic acids, in turn resulting in mutations and cell death.
- Denaturation: Extreme heat, and certain chemicals can alter protein shape and function by breaking its three-dimensional structure.
Relative Susceptibility of Microorganisms
- Enveloped viruses, gram-positive bacteria and non-enveloped viruses, fungi generally are more susceptible to microbial treatment.
- Gram-negative bacteria, active-stage protozoa, protozoa cysts, mycobacteria, bacterial endospores generally are more resistant.
Gram Positive vs Gram Negative Bacteria
- Gram-positive bacterial cell walls have a thick peptidoglycan layer, less complex and thus more penetrable to antimicrobial agents.
- Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides. This outer layer significantly reduces the penetration of many antimicrobial agents, thus higher resistance.
Strength of Germicides
- High-level: Kills all pathogens, including bacterial endospores (some aldehydes).
- Intermediate-level: Kills fungal spores, protozoan cysts, viruses, and pathogenic bacteria (some chlorine).
- Low-level: Kills vegetative bacteria, fungi, and protozoa (some alcohols, detergents/soaps).
Methods of Control: Physical vs Chemical
- Antimicrobial agents include physical factors (e.g., heat) and chemical factors (e.g., disinfectants, antibiotics).
- Bacterial populations treated with killing agents usually die at a constant rate.
Death Rate
- Bacterial populations die at a constant rate when exposed to killing agents, whether physical or chemical.
- The graph of bacterial population vs exposure time has a straight downwards slope.
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Description
This quiz explores the various methods of microbial control including physical and chemical techniques, terminology, and factors affecting the effectiveness of antimicrobial agents. Test your understanding of concepts like sanitization, disinfection, sterilization, and antisepsis.
