Questions and Answers
Physical agents for controlling microbial growth include all of the following, except:
Which of the following microbial forms have the highest resistance to physical and chemical controls?
The process that destroys or removes all microorganisms and microbial forms including bacterial endospores is:
The process of using a cleansing technique to mechanically remove and reduce microorganisms and debris to safe levels is:
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The use of a physical or chemical process to destroy vegetative pathogens on inanimate objects is:
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The use of chemical agents directly on exposed body surfaces to destroy or inhibit vegetative pathogens is:
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Scrubbing or immersing the skin in chemicals to reduce the numbers of microbes on the skin is:
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Which is correct regarding the rate of microbial death?
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Sterilization is achieved by:
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Dry heat is less efficient than moist heat.
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Endospores can be killed by:
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The minimum sterilizing conditions in a steam autoclave are:
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Disinfection of beverages, such as apple juice, milk, and wine, is optimally achieved by:
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Electrons are ejected from atoms in cells when organisms are exposed to:
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Which of the following items are typically irradiated in order to kill microbes?
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HEPA filters are used to remove microbes from:
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Which of the following does not contain a heavy metal?
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The easiest microbial forms to kill or inhibit are:
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Alcohols:
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All of the following are correct about iodophors, except:
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The sterilizing gas used in a special chamber is:
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The chemical agent that produces highly reactive hydroxyl-free radicals and also decomposes to O2 gas is:
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All the following are correct about detergents, except:
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Ethylene oxide is:
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Which of the following is officially accepted as a sterilant and high-level disinfectant?
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All of the following are correct about food irradiation, except:
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All of the following are methods of disinfection or sterilization, except:
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Which common hospital pathogen is able to grow abundantly in soap dishes?
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All of the following are correct about the autoclave, except:
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Which of the following types of agents targets protein conformation?
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Using toilet bowl cleaner and nonionizing radiation to inanimate surfaces only removes or kills vegetative bacteria. The term that best describes this action is:
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Which of these metals have antimicrobial properties associated with them?
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Commercial products containing which types of chemicals are more effective at killing microorganisms?
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Bacteriocidal agents are sterilants.
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Bacteriostatic agents kill bacterial cells.
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The presence of organic matter such as saliva and pus can interfere with the actions of disinfectants.
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When a control agent targets the metabolic processes of microbial cells, active younger cells typically die more rapidly than older cells.
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A microorganism that is not motile and has stopped metabolizing could be considered dead.
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Most microbial contaminants of food are killed at freezing temperatures.
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Filtration is an effective method to remove microbes from air and liquids.
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Chlorine compounds remain stable and effective in the presence of excess organic matter.
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Aniline dyes like crystal violet have antimicrobial activity particularly against gram-positive bacteria and some fungi.
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Alcohols are more effective at inactivating enveloped viruses than naked viruses.
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Isopropyl alcohol wiped across a skin site can sterilize it.
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Chlorine dioxide and ethylene oxide are gaseous sterilants.
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_____ heat is more rapidly effective and efficient compared to _____ heat.
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_____ radiation excites atoms to a higher energy state within molecules such as DNA that then leads to the formation of pyrimidine dimers.
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Some microbial control agents are able to _____ cell proteins by breaking bonds that maintain the native state, three-dimensional configuration of the proteins.
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_____ filters are widely used to provide a flow of sterile air to hospital rooms.
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_____ is a halogen used in gaseous and liquid form for large scale disinfection of drinking water and sewage.
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__________ or steam sterilization is the process by which steam is heated under pressure to sterilize objects.
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Study Notes
Microbial Control Methods
- Physical agents for controlling microbial growth include ultraviolet radiation, boiling water, HEPA filters, and pasteurization, but not hydrogen peroxide.
- Bacterial endospores demonstrate the highest resistance to both physical and chemical controls compared to naked viruses, protozoan cysts, fungal spores, and yeast.
Sterilization and Disinfection Processes
- Sterilization is the complete elimination of all microorganisms, including bacterial endospores.
- Sanitization involves the mechanical removal and reduction of microorganisms to safe levels.
- Disinfection targets vegetative pathogens on inanimate objects, while antisepsis aims to inhibit pathogens on exposed body surfaces.
Microbial Death Rates
- In a culture, cells generally exhibit a constant rate of death, contrasting the misconception of simultaneous cell death upon contact with control agents.
Autoclave and Heat Methods
- Effective sterilization with an autoclave requires conditions of 121°C at 15 psi for at least 15 minutes.
- Dry heat sterilization is generally less effective than moist heat methods.
Methods of Microbial Destruction
- Endospores can be effectively killed by dry heat at 170°C for 2 hours, incineration, or exposure to other viable chemical agents.
- Pasteurization is ideal for disinfecting beverages like apple juice, milk, and wine.
Chemical Agents and Their Functions
- Hydrogen peroxide generates hydroxyl-free radicals and decomposes to O2 gas, exhibiting significant antimicrobial activity.
- Alcohols are effective as skin degerming agents and denature proteins at concentrations between 50-95%.
- Ethylene oxide is a sporicidal gas used in specialized sterilization chambers.
Iodophors and Heavy Metals
- Iodophors combine iodine with a polymer to enhance penetration and reduce staining—the quick release of iodine is incorrect.
- Silver and gold exhibit antimicrobial properties, while other metals like tin and aluminum do not.
Filtration and Chemical Stabilization
- HEPA filters effectively remove microbes from air, while filtration remains a viable method for both air and liquid sterilization.
- Chlorine compounds lose effectiveness in the presence of excessive organic matter.
Misconceptions in Microbial Control
- Bacteriocidal agents do not necessarily guarantee sterilization, and bacteriostatic agents do not kill bacteria, merely inhibit their growth.
- The presence of organic matter can indeed interfere with disinfectant actions.
- Microbial contaminants in food are rarely killed at freezing temperatures.
General Principles of Microbial Control
- Moist heat is generally more effective than dry heat for sterilization processes.
- Nonionizing radiation causes DNA damage by forming pyrimidine dimers.
- Agents that denature proteins can disrupt their three-dimensional structure, impacting cell function.
Recap of Key Definitions
- Autoclaving or steam sterilization effectively combines steam and pressure for sterilizing objects.
- Chlorine, widely used for disinfecting water and sewage, acts as a halogen in both liquid and gaseous forms.
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Description
Explore various microbial control methods including physical agents, sterilization and disinfection processes. Learn about microbial death rates and the effectiveness of heat methods. This quiz will enhance your understanding of how different techniques influence microbial growth and survival.
