Sterilization Methods Practice Questions
20 free Sterilization Methods practice questions for the Microbiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is sterilization?
- A Reduction of the microbial population to safe levels
- B Elimination of all forms of life including spores
- C Inhibition of bacterial growth and reproduction
- D Removal of all visible dirt from instruments
Correct answer: Elimination of all forms of life including spores
Sterilization is the complete elimination of all microorganisms, including bacterial spores and viruses. It is more rigorous than disinfection or antisepsis.
Which method uses moist heat under pressure for sterilization?
- A Hot air oven
- B Autoclaving
- C Pasteurization
- D Filtration
Correct answer: Autoclaving
Autoclaving uses steam under pressure, typically at 121°C and 15 psi, to achieve sterilization. It effectively kills spores and resistant organisms.
What is the standard temperature and time for autoclaving?
- A 100°C for 10 minutes
- B 121°C for 15 minutes
- C 160°C for 2 hours
- D 180°C for 30 minutes
Correct answer: 121°C for 15 minutes
The standard autoclaving condition is 121°C for 15 minutes at 15 psi. This ensures complete destruction of all microorganisms including spores.
Which sterilization method is suitable for heat-sensitive materials?
- A Dry heat
- B Autoclaving
- C Filtration
- D Incineration
Correct answer: Filtration
Filtration removes microorganisms without using heat. It is ideal for sterilizing heat-sensitive liquids like antibiotics and vaccines.
Which method uses dry heat for sterilization?
- A Autoclave
- B Hot air oven
- C Boiling
- D UV radiation
Correct answer: Hot air oven
A hot air oven uses dry heat, typically at 160–180°C, to sterilize materials. It is suitable for glassware and metal instruments.
Which method is used to sterilize surgical instruments using direct flame?
- A Autoclaving
- B Incineration
- C Flaming
- D Boiling
Correct answer: Flaming
Flaming involves passing instruments through a flame to kill microorganisms. It is commonly used for inoculating loops.
Which sterilization method uses high-energy radiation?
- A UV radiation
- B Gamma radiation
- C Microwave radiation
- D Infrared radiation
Correct answer: Gamma radiation
Gamma radiation is a form of ionizing radiation used for sterilization. It penetrates deeply and is used for disposable medical supplies.
Which type of radiation is commonly used for surface sterilization?
- A Gamma radiation
- B X-rays
- C UV radiation
- D Infrared radiation
Correct answer: UV radiation
UV radiation is used for surface sterilization as it has limited penetration. It damages microbial DNA, preventing replication.
Which chemical is commonly used for gas sterilization?
- A Ethanol
- B Chlorine
- C Ethylene oxide
- D Hydrogen peroxide
Correct answer: Ethylene oxide
Ethylene oxide gas is used for sterilizing heat-sensitive medical equipment. It penetrates materials and kills microorganisms effectively.
Which method involves burning materials to ashes?
- A Autoclaving
- B Incineration
- C Filtration
- D Pasteurization
Correct answer: Incineration
Incineration involves burning materials at high temperatures until they are reduced to ash. It is used for waste disposal and sterilization.
Which sterilization method is used for culture media preparation?
- A Filtration
- B UV radiation
- C Dry heat
- D Autoclaving
Correct answer: Autoclaving
Autoclaving is commonly used to sterilize culture media. It ensures all microorganisms and spores are destroyed.
Which factor is most important for effective autoclaving?
- A Time and temperature at ambient pressure
- B Temperature and pressure regardless of duration
- C Pressure and time with minimal heat required
- D Combination of time, temperature, and pressure
Correct answer: Combination of time, temperature, and pressure
Effective autoclaving requires the correct combination of temperature, pressure, and time. All these factors ensure complete sterilization.
Which method is least effective against bacterial spores?
- A Autoclaving
- B Dry heat
- C Boiling water
- D Gamma radiation
Correct answer: Boiling water
Boiling may kill vegetative cells but is not effective against spores. Sterilization methods like autoclaving are required to destroy spores.
Which sterilization method uses membranes with specific pore sizes?
- A Filtration
- B Autoclaving
- C Radiation
- D Dry heat
Correct answer: Filtration
Filtration uses membranes with small pores to physically remove microorganisms. It is widely used for sterilizing liquids.
Which indicator is used to verify autoclave sterilization?
- A Biological indicator
- B pH indicator
- C Temperature indicator
- D Pressure gauge
Correct answer: Biological indicator
Biological indicators containing spores are used to verify sterilization. Their absence after treatment confirms effectiveness.
Which sterilization method is used for disposable syringes?
- A Autoclaving
- B Dry heat
- C Boiling
- D Gamma rays
Correct answer: Gamma rays
Gamma radiation is used for sterilizing disposable medical equipment like syringes. It ensures sterility without heat damage.
Which process uses liquid chemical agents at high concentrations to eliminate all microorganisms?
- A Antiseptic application
- B Surface disinfection
- C Thermal pasteurization
- D Chemical sterilization
Correct answer: Chemical sterilization
Chemical sterilization uses strong chemicals like glutaraldehyde to achieve sterilization. It is used for heat-sensitive instruments.
Which sterilization method is most suitable for oils and powders?
- A Autoclaving
- B Filtration
- C Flaming
- D Dry heat
Correct answer: Dry heat
Dry heat is suitable for sterilizing oils and powders that cannot be penetrated by steam. It requires higher temperatures and longer durations.
Which method reduces microbial load but does not achieve sterilization?
- A Disinfection
- B Sterilization
- C Autoclaving
- D Incineration
Correct answer: Disinfection
Disinfection reduces the number of microorganisms but may not eliminate all spores. It is less effective than sterilization.
Which factor affects the efficiency of chemical sterilization?
- A Presence of organic matter
- B Color of the material surface
- C Shape of the container used
- D Type of label attached
Correct answer: Presence of organic matter
Organic matter can interfere with chemical sterilants and reduce their effectiveness. Proper cleaning is essential before sterilization.