All Free Microbiology MCQs with Answers

• 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…

• A. Gamma-Rays
• B. X-Rays
• C. Autoclaving
• D. Boiling

Explanation: Gamma irradiation is used industrially to sterilise prepackaged surgical needles and sutures because it penetrates sealed materials and…

• A. Robert Koch
• B. Joeph Lister
• C. John Hunter
• D. Alexander flemings

Explanation: Joseph Lister introduced antiseptic surgical practice, which is commonly credited in basic microbiology questions with establishing…

• A. Autoclaving
• B. Hot air oven
• C. Inspissation
• D. Tyndallization

Explanation: Dry dressing powders are sterilised in a hot-air oven because they may be damaged by moisture and are unsuitable for steam penetration.

• A. Brucella
• B. Mycobacterium
• C. Salmonella
• D. Coxiella burnetti

Explanation: Coxiella burnetii is unusually resistant to heat and may survive ordinary pasteurisation conditions, so it requires more stringent…

• A. Using chemical indicator strip or pouch
• B. Recording a temperature/ pressure readings from sterilizer guage
• C. Using a bacterial spore test
• D. Determining the ability of a sterilizer to kill the hepatitis B virus

Explanation: A bacterial spore test is the best practical indicator because resistant spores directly demonstrate whether the sterilisation process can…

• A. Autoclaving
• B. Hot air oven
• C. Incineration
• D. Formaldehyde

Explanation: Glassware is usually sterilised in a hot-air oven because dry heat avoids moisture and is suitable for glass and other heat-stable…

• A. Carbolic acid spraying
• B. Washing with soap and water
• C. Formaldehyde fumigation
• D. ETO gas

Explanation: Formaldehyde fumigation is used to disinfect and sterilize enclosed areas such as operation theatres, including surfaces and air.

• A. Incineration
• B. Dumping
• C. Autoclaving
• D. Burying

Explanation: Incineration destroys contaminated dressings by burning them at high temperature, reducing both pathogens and waste volume.

• A. using Bacillus stearo thermo philus
• B. Using non-pathogenic strain of clostridium tetani
• C. Using chemical indicator
• D. Using methylene blue

Explanation: Bacillus stearothermophilus, now called Geobacillus stearothermophilus, is used as a biological indicator for moist-heat sterilisation…