30 Questions
What is the purpose of using phenol coefficient in measuring bactericidal potency of new chemicals?
To compare the effectiveness of the new chemical agent to the reference standard (phenol)
How do organic solvents like alcohol affect the cell membrane?
They disorganize the cell membrane lipid structure.
What is the main difference between sterilization and disinfection?
Sterilization destroys all forms of microbial life including spores, while disinfection only destroys microbes that cause disease and may not be effective in killing spores.
What is antisepsis and how does it differ from disinfection?
Antisepsis is the destruction or inhibition of microorganisms in living tissue to prevent harmful infections. Disinfection, on the other hand, targets microbes that cause disease but may not be effective in killing spores.
What is the main effect of acids and alkalies on proteins?
They cause conformational alteration of proteins, resulting in irregular looping and coiling of the polypeptide chain.
What is the mechanism of action of dry heat?
Denatures protein
Explain the concept of aseptic techniques and provide an application.
Aseptic techniques are used in microbiological research, food preservation, and disease prevention. For example, maintaining sterility during surgical procedures.
How do heavy metals like mercurials modify functional groups of proteins and nucleic acids?
They interact with functional groups of proteins and nucleic acids.
What factors affect the efficacy of chemical agents in sterilization and disinfection?
The concentration of the agent, time of exposure, and temperature can influence the efficacy of chemical agents.
What is the clinical reason for not using phenolic compounds despite their effectiveness in Gram positive bacteria?
Due to their neurotoxic effects.
Why is moist heat preferred over dry heat?
More rapid killing
Why is it important to use sterile apparatus and culture media in laboratory work with pure cultures?
Using sterile apparatus and culture media is crucial to prevent contamination and ensure the purity of the cultures being studied.
What is the optimal concentration of ethanol for it to be a potent skin disinfectant?
70%
What is the temperature range used in applying dry heat for sterilization?
160 - 1000C for 1 hour
What is the purpose of Tyndallization as a method of sterilization?
Intermittent sterilization
How do chemical methods of sterilization and disinfection differ from antibiotics?
Chemical agents used for sterilization and disinfection do not show selectivity and can destroy any type of microbe, unlike antibiotics.
What is the temperature and duration used in pasteurization?
62oC for 30 minutes (Holder method) or 72oC for 15 seconds (Flash method)
What is the purpose of applying rapid cooling after pasteurization?
To discourage bacterial growth
What is the purpose of using Ethylene oxide as a sterilizing agent?
Sterilize medical-surgical devices that would be damaged by heat.
What are the characteristics of Antiseptic Agents mentioned in the text?
Never be toxic to cells, never be corrosive, should never change nature of skin.
What is the purpose of the Phenol Coefficient Test?
To compare the potency of a disinfectant with that of phenol.
What does the Minimum Inhibitory Concentration (MIC) test measure?
The lowest concentration of disinfectant that inhibits the growth of S.typhi in a nutrient medium.
What is the purpose of the Kelsey-Sykes test (Capacity test)?
To measure the capacity of the disinfectant to cope with successive bacterial invasions.
What is mentioned as the most reliable and universally applicable method of sterilization in the text?
Heat
What is the principle behind autoclaving?
When water is boiled at increased pressure, hot saturated steam is formed which penetrates and gives up its latent heat when it condenses on cooler objects.
What are the characteristics of hot saturated steam in autoclaving that make it an excellent agent for sterilization?
High temperature, high latent heat, ability to form water of condensation, and contraction in volume during condensation.
What conditions are typically used for sterilizing most culture media in autoclaving?
Pressure of 15 lb/in², temperature of 121°C, for 15 minutes.
How can the completion of sterilization in an autoclave be visually confirmed?
Color change of autoclave tape from blue to brown-black.
What biological control method is used to ensure proper sterilization in an autoclave?
Using paper strips impregnated with spores of Bacillus subtilis subsp. niger.
What are the recommended sterilization controls for moist heat in an autoclave?
Recording temperature and time of each cycle, using heat-sensitive autoclave tape, and using biological indicators.
Test your knowledge on chemical sterilization agents used for medical-surgical instruments and devices. Learn about the effectiveness and usage of glutaraldehyde, cold sterilization, ethylene oxide gas, and antiseptic agents that modify functional groups of proteins and nucleic acids.
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