Free Infection Control and Sterilisation MCQs with Answers

• A. Boiling
• B. Ethanol
• C. Cidex
• D. All of the above

Explanation: HIV is readily inactivated outside the body by heat such as boiling, suitable concentrations of ethanol, and glutaraldehyde-based…

• A. Mycobacteria
• B. Spore
• C. Prions
• D. Coccidia

Explanation: Prions are the most resistant infectious agents to routine antiseptics, disinfectants and sterilisation methods because they contain…

• A. HIV
• B. Hepatitis C
• C. Hepatitis B
• D. Hepatitis E

Explanation: Dental instruments contaminated with blood can transmit HIV, hepatitis B, and hepatitis C.

• A. 1-2% cetrimide
• B. 100% alcohol
• C. 2% Lysol
• D. 5% chloroxylene

Explanation: Absolute alcohol is not a reliable disinfectant because water is needed for effective protein denaturation; about 70% alcohol is generally…

• A. Hot air oven
• B. Auto claving
• C. Irradiation
• D. Ethylene dioxide

Explanation: Oil and grease are moisture-free materials and are sterilized by dry heat in a hot-air oven.

• A. Glassware
• B. Rubber tubes
• C. Sharp instrument
• D. Liquid paraffin

Explanation: Hot-air ovens are suitable for glassware, metal sharp instruments and oils such as liquid paraffin.

• A. Ultra violet rays
• B. Ultrasonic vibrations
• C. Infrared rays
• D. Gamma rays

Explanation: Cold sterilisation uses ionising radiation, especially gamma rays, to destroy microorganisms without substantial heating.

• A. 125°C for new seconds
• B. 60°C for 15 minutes
• C. 72°C for 5 minutes
• D. 72° for 15 - 20 Sec

Explanation: Flash, or high-temperature short-time, pasteurisation heats milk to about 72°C for 15 seconds.

• A. Lysis
• B. Oxidation
• C. Hydrolysis of DNA
• D. Coagulation of proteins

Explanation: Dry heat kills microorganisms mainly by oxidative damage to cellular components, with dehydration also contributing.

• A. It can kill hepatitis B virus
• B. Used for sterilizing surgical instruments
• C. Can kill mycobacterium tuberculosis
• D. Can kill vegetative bacterial cells

Explanation: Boiling kills many vegetative bacteria, including Mycobacterium tuberculosis, and can inactivate hepatitis B virus, but it does not…

• A. Long wavelength
• B. short wave lenght
• C. Ozone
• D. Heat

Explanation: The germicidal effect of sunlight is mainly due to its ultraviolet component, which has short wavelengths and damages microbial DNA.

• A. One day
• B. Two successive days
• C. 60 minutes
• D. Three successive days

Explanation: Tyndallisation is intermittent steaming, usually for about 20 to 30 minutes on each of three successive days.

• A. Hot air oven
• B. U.V. rays
• C. Gamma rays
• D. Boiling

Explanation: Gamma rays penetrate sealed packages and sterilize disposable syringes without heating or opening them.

• A. It has got more bactericidal activity
• B. It has got more bacteriostatic activity
• C. It has got no deleterious effect on the cement and lenses of instruments
• D. Its application is easier

Explanation: Glutaraldehyde is preferred because it is less damaging to instrument cement, lenses and delicate materials while still providing…

• A. Autoclaving
• B. Hot air oven
• C. UV-Radiation
• D. Inspissation

Explanation: Liquid paraffin is sterilized by dry heat in a hot-air oven because it is non-aqueous and would not be reliably sterilized by steam…

• A. 20% phenol
• B. High efficiency particle arrestors
• C. 40% formaldehyde vapour
• D. Chlorine gas

Explanation: Rooms can be disinfected by formaldehyde vapour, commonly generated from concentrated formaldehyde solution.

• A. Lipids
• B. Carbohydrates
• C. Inorganic salts
• D. Nucleic acids

Explanation: Ultraviolet radiation damages nucleic acids by producing pyrimidine dimers, especially in DNA, which blocks replication and transcription.

• A. Disinfection kills all spores but sterilization does not
• B. Sterilization kills all spores but disinfection does not
• C. Sterilization involves chemicals and disinfection involves physical methods
• D. Sterilization is easier to achieve

Explanation: Sterilization destroys all forms of microbial life, including bacterial spores, whereas disinfection may leave spores and some highly…

• A. Clothes
• B. Instruments
• C. Culture media
• D. Needles

Explanation: Culture media are generally sterilised by moist heat in an autoclave because dry heat may cause dehydration or decomposition.

• A. Kill all pathogenic micro-organisms
• B. Kill all non-pathogenic micro-organisms in the environment
• C. Deactivate all pathogens not spores
• D. Deactivate all spores and dill pathogenic organism

Explanation: Sterilisation means destruction or removal of all forms of microbial life, including bacterial spores, rather than merely killing…