MCQs MICROBIOLOGY: Physical and Chemical Agents

1.
Which of the following articles can be sterilized in an autoclave?

A. Gloves
B. Culture media
C. Dressing material
D. All of these
Answer & Explanation
Answer: Option D

2.
Which of the following disinfectants act by disrupting microbial membranes?

A. Cationic detergents
B. Halogens
C. Heavy metals
D. Aldehydes
Answer & Explanation
Answer: Option A

3.
Which of the following is best to sterilize heat labile solutions?

A. Dry heat
B. Autoclave
C. Membrane filtration
D. Pasteurization
Answer & Explanation
Answer: Option C

4.
The time required to kill 90% of the microorganisms in a sample at a specific temperature is the

A. decimal reduction time
B. thermal death point
C. F value
D. D value
Answer & Explanation
Answer: Option D

5.
Which of the following is best used for long term storage of microbial samples when carried out properly?

A. Storage in a freezer at -10°C
B. Storage in a freezer at ultra low temperatures (-70°C)
C. Storage in a refrigerator on an agar slant
D. Storage on a petri plate at room temperature
Answer & Explanation
Answer: Option B

6.
Which of the following is not a disinfectant containing a heavy metal?

A. Silver nitrate
B. Mercurochrome
C. Copper sulfate
D. Chlorine
Answer & Explanation
Answer: Option D

7.
Which is the most important surface active disinfectants?

A. Amphoteric compounds
B. Cationic compounds
C. Non-ionic compounds
D. Anionic compounds
Answer & Explanation
Answer: Option B

8.
Which disinfectant would be most effective against Staphylococcus found in a blood spill?

A. Phenol
B. Cetylpyridinium chloride
C. Hexachlorophene
D. None of these
Answer & Explanation
Answer: Option D

9.
Which of the following substances can sterilize?

A. Alcohol
B. Cetylpyridinium chloride
C. Ethylene oxide
D. Chlorine
Answer & Explanation
Answer: Option C

10.
Milk is pasteurized in batch method by keeping it at

A. 63°C for 30 minutes
B. 72°C for 60 seconds
C. 73°C for 30 minutes
D. 72°C for 6 minutes
Answer & Explanation
Answer: Option A

11.
Preservation of foods by using salts and sugars works by

A. raising pH
B. lowering osmotic pressure
C. creating a hypertonic environment
D. creating a hypotonic environment
Answer & Explanation
Answer: Option C

12.
Which of the following items could be sterilized by dry heat sterilization?

A. Intravenous (IV) solution
B. Plastic IV bags
C. Glass pipettes
D. rubber gloves
Answer & Explanation
Answer: Option C

13.
Which of the following does not kill endospores?

A. Autoclave
B. Incineration
C. Hot air sterilization
D. Pasteurization
Answer & Explanation
Answer: Option D

14.
Which disinfectant was the most effective against Salmonella"?

A. Phenol
B. Cetylpyridinium chloride
C. Hexachlorophene
D. Merthiolate
Answer & Explanation
Answer: Option D

15.
If a canning procedure is not properly followed, which type of microbe is most likely to grow in the canned food?

A. Obligate Aerobe
B. Acidophile
C. Mesophile
D. Obligate Anaerobe
Answer & Explanation
Answer: Option D

16.
Bactericidal concentration of phenol is

A. 0.25% B. 0.5%
C. 0.75% D. 1%
Answer & Explanation
Answer: Option D

17.
Which of the following is most effective for sterilizing mattresses and plastic petri plates?

A. Chlorine
B. Ethylene oxide
C. Glutaraldehyde
D. Ultraviolet radiation
Answer & Explanation
Answer: Option B

18.
Which of the following skin disinfectant(s) is/are most frequently used?

A. Isopropyl alcohol
B. Ethyl alcohol
C. Both (a) and (b)
D. none of these
Answer & Explanation
Answer: Option C

19.
All of the following are sporicidal except

A. glutaraldehyde
B. ethylene oxide
C. formaldehyde
D. alcohol
Answer & Explanation
Answer: Option D

20.
Which of the following describes the effect of ionizing radiation on microbes?

A. Changes the 3-dimensional structure of proteins to a 2-dimen-sional form
B. Substantially decreases enzymatic activity, slowing microbial reproduction
C. Induces electrons and protons to jump out of the molecules of the microbe
D. None of the above
Answer & Explanation
Answer: Option C

 

21.
The process of making an object free from living organisms including bacterial and fungal spores and viruses is known as

A. pasteurization B. antisepsis
C. disinfection D. sterilization
Answer & Explanation
Answer: Option D


22.
Media containing spores and thermolabile constituents are sterilized by

A. pasteurization
B. UV radiation
C. dry heat
D. tyndalization
Answer & Explanation
Answer: Option B

23.
A(n)____is used to prevent infection by killing or inhibiting pathogen growth on animal tissues.

A. bacteriostatic agent
B. sanitizer
C. disinfectant
D. antiseptic
Answer & Explanation
Answer: Option D

24.
One drawback to the use of ultraviolet light as a sterilizing agent is its

A. failure to kill bacteria
B. failure to bacterial spores
C. failure to kill microbes in a closed environment
D. failure to kill microbes located in the center of an object
Answer & Explanation
Answer: Option D

25.
Ethylene oxide is used to destroy or kill which of the following microbes?

A. Bacteria
B. Spores
C. Fungi
D. All of these
Answer & Explanation
Answer: Option D

26.
Which of the following was the first widely used antiseptic and disinfectant?

A. Chlorine B. Phenol
C. Iodine D. Alcohol
Answer & Explanation
Answer: Option B

27.
If a 1:600 dilution of a test compound kills a standard population of Staphylococcus aureus in 10 minutes but not 5 minutes while a 1:60 dilution of phenol kills the population in the same time, what is the phenol coefficient of the test compound?

A. 1 B. 5
C. 10 D. 50
Answer & Explanation
Answer: Option C

28.
Microbes can be removed from a liquid solution by the process of

A. filtration B. freeze-drying
C. osmosis D. desiccation
Answer & Explanation
Answer: Option A

29.
Which of the following is bactericidal?

A. Membrane filtration
B. Ionizing radiation
C. Freeze-drying
D. Deep freezing
Answer & Explanation
Answer: Option B

30.
Which of the following process can be efficiently carried out by incineration?

A. Sterilization of scalpel blades and needles
B. Sterilization of all glass syringes
C. Sterilization of points of forceps
D. Destruction of contaminated materials
Answer & Explanation
31.
The organisms retained in the fluids filtered by Seitz filter is

A. Proteus
B. Staphylococcus
C. Clostridium
D. None of these
Answer & Explanation
Answer: Option D


32.
Which of the following material is sterilized by heating at 160°C in a hot air oven for one hour?

A. Swab sticks
B. All-glass syringes
C. Oils and jellies
D. All of these
Answer & Explanation
Answer: Option D


33.
For sterilization of which material gamma rays can be used?

A. Catheters
B. Plastic syringes
C. Canulas
D. None of these
Answer & Explanation
Answer: Option D


34.
Which of the following is sterilized with the help of glutaraldehyde?

A. Thermometers
B. Bronchoscopes
C. Cystoscopes
D. All of these
Answer & Explanation
Answer: Option D


35.
The time in minutes at a specific temperature needed to kill a population of cells is the

A. decimal reduction time
B. thermal death point
C. thermal death temperature
D. F value
Answer & Explanation
Answer: Option D

 

36.
Which of the following is a limitation of the autoclave?

A. It takes too long to sterilize
B. It lacks the ability to inactivate viruses
C. It lacks the ability to kill endospores
D. It will destroy heat labile materials
Answer & Explanation
Answer: Option D

37.
Which of the following has most heat resistant spores?

A. Clostridium histolyticum
B. Clostridium perfringens
C. Bacillus stearothermophilus
D. Bacillus cereus
Answer & Explanation
Answer: Option C

38.
The lowest temperature that kills all microorganisms in a liquid suspension in 10 minutes is known as the

A. decimal reduction time
B. thermal death point
C. thermal death temperature
D. thermal death time
Answer & Explanation
Answer: Option B

39.
Which of the following tests is designed to simulate the natural conditions under which the disinfectants are used in hospitals?

A. Phenol coefficient test
B. Minimum inhibitory concentration test
C. Capacity test
D. None of these
Answer & Explanation
Answer: Option C

40.
Steam exposure of a material at 100°C for 20 minutes for three consecutive days is known as

A. inspissation
B. tyndallization
C. autoclaving
D. none of these
Answer & Explanation
Answer: Option B


41.
Which of the following material is sterilized by use of red heat?

A. Soiled dressings
B. Inoculating wires and loops
C. Glass slides
D. All-glass syringes
Answer & Explanation
Answer: Option B

42.
Which of the following methods will not sterilize?

A. Aqueous glutaraldehyde for 10 hours
B. Dry heat at 171°C for 1 to 2 hours
C. 121°C at 15 lb/in pressure for 15 to 20 minutes
D. 100°C boiling water for 30 minutes
Answer & Explanation
Answer: Option D

43.
Which of the following is/are vapour-phase disinfectant/s?

A. Formaldehyde
B. Ethylene oxide
C. Both (a) and (b)
D. None of these
Answer & Explanation
Answer: Option C

44.
Sweet and salty foods frequently don't require refrigeration to prevent spoilage because they have

A. insufficient nutrients
B. low pH
C. high concentration of solutes
D. toxic alkaline chemicals
Answer & Explanation
Answer: Option C

45.
Iodophores are mixture of

A. iodine and aldehydes
B. iodine and surface active agents
C. iodine and alcohols
D. iodine and phenols
Answer & Explanation
Answer: Option B

46.
Which of the following compounds are commonly used as general antiseptics to treat cuts and scratches?

A. Aldehydes
B. Ethylene oxide
C. Halogens
D. None of these
Answer & Explanation
Answer: Option C

47.
Complete destruction of the microorganisms is commonly known as

A. disinfection
B. sterilization
C. antisepsis
D. none of these
Answer & Explanation
Answer: Option C