Disinfection, Antisepsis, and Bactericidal Agents Quiz

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Questions and Answers

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?

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?

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?

Ionizing Radiation Signup and view all the answers

What is the primary use of FILTRATION in microbiology?

To separate microorganisms from fluids Signup and view all the answers

When is Ultraviolet light commonly used for disinfection?

In sterilizing hospital rooms and laboratories Signup and view all the answers

Which type of agents remove dirt through emulsification and are most effective at acidic pH?

Anionic Agents Signup and view all the answers

What type of agents are quaternary ammonium compounds like Zephiran?

Cationic Agents Signup and view all the answers

Why is phenol no longer used as a disinfectant?

It is toxic to human cells Signup and view all the answers

Which compound is used as a gold standard in the chemical evaluation of new disinfectants?

Phenol Signup and view all the answers

In what solution is Chlorhexidine used as a skin disinfectant?

Isopropanol solution Signup and view all the answers

Which compound is effective against most gram-positive bacteria and is used for topical purposes?

Chloroxylenols Signup and view all the answers

Which factor contributes to a higher killing action of a chemical agent?

Higher concentration Signup and view all the answers

What concentration range is effective as a bactericidal for alcohol?

50 - 80% Signup and view all the answers

How does temperature affect the killing action of chemical agents?

Higher temperature accelerates killing action Signup and view all the answers

What factor may decrease the efficiency of a chemical agent in killing microorganisms?

Presence of extraneous materials Signup and view all the answers

Which type of bacteria may be resistant to most chemical agents?

Bacteria that produce endospores Signup and view all the answers

What is the main characteristic of triclosan's activity against bacteria?

Activity mainly against gram-positive bacteria Signup and view all the answers

How does the number of organisms affect the time needed for a disinfectant to destroy them?

The larger the number of organisms, the more time needed Signup and view all the answers

Which type of alcohol has greater bactericidal activity than ethyl alcohol?

Isopropyl Alcohol Signup and view all the answers

Which substance causes denaturation of cellular proteins leading to the destruction of bacterial cells?

Alcohol and acetone Signup and view all the answers

Which chlorinated diphenyl has greater activity against gram-positive bacteria similar to chloroxylenols?

Hexachlorophene Signup and view all the answers

What is the main effect of alcohols on the cell membrane?

Disorganize the lipid structure of the cell membrane Signup and view all the answers

What is the main use of methyl alcohol as described in the text?

As a fungicidal and sporicidal agent Signup and view all the answers

Which process involves killing most microbial forms on inanimate objects without necessarily destroying saprophytes and bacterial endospores?

Disinfection Signup and view all the answers

What is the term for the use of chemical agents on living tissue to prevent the spread of microorganisms?

Antisepsis Signup and view all the answers

What is the term for an agent capable of inhibiting the growth of bacteria without necessarily killing them?

Bacteriostatic agent Signup and view all the answers

What does thermal death time refer to in sterilization through heating?

The minimum time required to kill organisms at a predetermined temperature and environment Signup and view all the answers

Why is moist heat preferred over dry heat for sterilization?

Moist heat has a more rapid killing action Signup and view all the answers

Which physical method of sterilization is the most common?

Heating Signup and view all the answers

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.