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Questions and Answers
What is the main purpose of LYOPHILIZATION in the laboratory?
What is the main purpose of LYOPHILIZATION in the laboratory?
- To separate microorganisms from the fluid
- To kill microorganisms in culture media
- To prepare suspensions of viruses and phages
- To rapidly freeze and dehydrate microorganisms for preservation (correct)
How does Ultraviolet light (UVL) act on bacterial DNA?
How does Ultraviolet light (UVL) act on bacterial DNA?
- By promoting DNA repair mechanisms
- By increasing the DNA replication rate
- By enhancing hydrogen bonds in the DNA
- By causing formation of thymine dimers in the DNA (correct)
What is the mechanism of action of Ionizing Radiation on microorganisms?
What is the mechanism of action of Ionizing Radiation on microorganisms?
- By inhibiting DNA synthesis
- By increasing cell membrane permeability
- By inducing formation of free radicals that interact with proteins and nucleic acids (correct)
- By promoting cell growth
Which form of radiation has greater penetrance: Ultraviolet light or Ionizing Radiation?
Which form of radiation has greater penetrance: Ultraviolet light or Ionizing Radiation?
What is the primary use of FILTRATION in microbiology?
What is the primary use of FILTRATION in microbiology?
When is Ultraviolet light commonly used for disinfection?
When is Ultraviolet light commonly used for disinfection?
Which type of agents remove dirt through emulsification and are most effective at acidic pH?
Which type of agents remove dirt through emulsification and are most effective at acidic pH?
What type of agents are quaternary ammonium compounds like Zephiran?
What type of agents are quaternary ammonium compounds like Zephiran?
Why is phenol no longer used as a disinfectant?
Why is phenol no longer used as a disinfectant?
Which compound is used as a gold standard in the chemical evaluation of new disinfectants?
Which compound is used as a gold standard in the chemical evaluation of new disinfectants?
In what solution is Chlorhexidine used as a skin disinfectant?
In what solution is Chlorhexidine used as a skin disinfectant?
Which compound is effective against most gram-positive bacteria and is used for topical purposes?
Which compound is effective against most gram-positive bacteria and is used for topical purposes?
Which factor contributes to a higher killing action of a chemical agent?
Which factor contributes to a higher killing action of a chemical agent?
What concentration range is effective as a bactericidal for alcohol?
What concentration range is effective as a bactericidal for alcohol?
How does temperature affect the killing action of chemical agents?
How does temperature affect the killing action of chemical agents?
What factor may decrease the efficiency of a chemical agent in killing microorganisms?
What factor may decrease the efficiency of a chemical agent in killing microorganisms?
Which type of bacteria may be resistant to most chemical agents?
Which type of bacteria may be resistant to most chemical agents?
What is the main characteristic of triclosan's activity against bacteria?
What is the main characteristic of triclosan's activity against bacteria?
How does the number of organisms affect the time needed for a disinfectant to destroy them?
How does the number of organisms affect the time needed for a disinfectant to destroy them?
Which type of alcohol has greater bactericidal activity than ethyl alcohol?
Which type of alcohol has greater bactericidal activity than ethyl alcohol?
Which substance causes denaturation of cellular proteins leading to the destruction of bacterial cells?
Which substance causes denaturation of cellular proteins leading to the destruction of bacterial cells?
Which chlorinated diphenyl has greater activity against gram-positive bacteria similar to chloroxylenols?
Which chlorinated diphenyl has greater activity against gram-positive bacteria similar to chloroxylenols?
What is the main effect of alcohols on the cell membrane?
What is the main effect of alcohols on the cell membrane?
What is the main use of methyl alcohol as described in the text?
What is the main use of methyl alcohol as described in the text?
Which process involves killing most microbial forms on inanimate objects without necessarily destroying saprophytes and bacterial endospores?
Which process involves killing most microbial forms on inanimate objects without necessarily destroying saprophytes and bacterial endospores?
What is the term for the use of chemical agents on living tissue to prevent the spread of microorganisms?
What is the term for the use of chemical agents on living tissue to prevent the spread of microorganisms?
What is the term for an agent capable of inhibiting the growth of bacteria without necessarily killing them?
What is the term for an agent capable of inhibiting the growth of bacteria without necessarily killing them?
What does thermal death time refer to in sterilization through heating?
What does thermal death time refer to in sterilization through heating?
Why is moist heat preferred over dry heat for sterilization?
Why is moist heat preferred over dry heat for sterilization?
Which physical method of sterilization is the most common?
Which physical method of sterilization is the most common?
Study Notes
Laboratory Preservation
- Lyophilization or freezing-drying is used to preserve microorganisms in a laboratory setting
- The process involves rapidly freezing the organism, then dehydrating it in a high vacuum and storing it in a vacuum-sealed container
Filtration
- Filtration is a form of mechanical sieving that separates microorganisms from fluid
- It does not kill microorganisms, but is used to remove bacteria from culture media or to prepare suspensions of viruses and phages
- Used for liquid solutions or urea solution
Radiation
- Ultraviolet light (UVL) is a non-ionizing radiation that disrupts H-bonds in bacterial DNA, causing lethal frame shift mutations
- UVL is used to disinfect hospital wards, operating rooms, and laboratories, but has poor penetrating ability
- Ionizing radiation has greater penetrance than UVL and exerts its effect by forming free radicals that interact with proteins and nucleic acids, resulting in cell death
Chemical Disinfection
- Surface active agents include cationic agents (e.g., Zephiran) and anionic agents (e.g., soap and bile salts)
- Phenolic compounds (e.g., phenol and cresols) are bactericidal and fungicidal, but have poor activity against spores and most viruses
- Chlorhexidine is used as a skin disinfectant and antiseptic hand wash
- Chloroxylenols are used for topical purposes and are effective against gram-positive bacteria
- Factors that affect the efficiency of chemical disinfection include:
- Concentration of the chemical agent
- Duration of exposure
- Temperature
- Nature of the surrounding medium
- Nature of the organism
- Number of organisms/size of inoculum
Antimicrobial Agents
- Alcohols (e.g., ethyl, isopropyl, and benzyl) disorganize the lipid structure of the cell membrane, dehydrate cells, and cause denaturation and coagulation of cellular proteins
- Hexachlorophene has greater activity against gram-positive bacteria
- Triclosan has good activity against gram-positive bacteria and some gram-negative bacteria
- Denaturation of cellular proteins can lead to the destruction of bacterial cells
Disinfection and Antisepsis
- Disinfection is the process of killing most microbial forms on inanimate objects to reduce the number of organisms to a level that cannot produce infection
- Antisepsis is the use of chemical agents on living tissue to prevent the spread of microorganisms
- Bactericidal or germicidal agents kill bacteria, while bacteriostatic agents inhibit the growth of bacteria without killing them
- Sporicidal, fungicidal, and viricidal agents destroy spores, fungi, and viruses, respectively
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Description
Test your knowledge on the processes of disinfection, antiseptics, and bactericidal agents. Learn about how these methods help in killing microbial forms on objects and preventing the spread of microorganisms on living tissues.
