Here are the first 10 MCQs formatted in plain text.
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1. What is the primary difference between disinfectants and antiseptics?
A. Disinfectants are used on living tissues, while antiseptics are used on inanimate objects.
B. Disinfectants are used on inanimate objects, while antiseptics are used on living tissues.
C. Disinfectants and antiseptics are interchangeable.
D. Disinfectants are more effective than antiseptics.
Answer: B
2. What is the main purpose of a biocide?
A. To inhibit bacterial reproduction.
B. To inactivate or kill microorganisms.
C. To destroy organic material on surfaces.
D. To increase microbial resistance.
Answer: B
3. Which of the following is NOT a characteristic of phenolics?
A. Stable and effective in the presence of organic matter.
B. Effective against spores.
C. Persist on surfaces after application.
D. Cause leakage of cellular contents by damaging membranes.
Answer: B
4. What factor enhances the effectiveness of most disinfectants?
A. Increased water hardness.
B. Lower concentration of disinfectant.
C. Higher temperature.
D. Reduced exposure time.
Answer: C
5. Which of the following halogens is commonly used as a disinfectant?
A. Sodium chloride
B. Iodine
C. Calcium carbonate
D. Potassium
Answer: B
6. What is the mechanism of action of alcohol as a disinfectant?
A. Oxidizing nucleic acids.
B. Denaturing proteins and dissolving membrane lipids.
C. Inhibiting bacterial DNA replication.
D. Disrupting glycolysis in microbes.
Answer: B
7. Which of the following is a gaseous agent used for sterilization?
A. Ethylene oxide
B. Glutaraldehyde
C. Hydrogen peroxide
D. Formalin
Answer: A
8. Which chemical agent is most effective for sterilizing thermolabile materials?
A. Phenol
B. Alcohol
C. Ethylene oxide
D. Iodine
Answer: C
9. Why are aldehydes effective antimicrobial agents?
A. They lower the surface tension of water.
B. They alkylate proteins and nucleic acids.
C. They oxidize enzymes.
D. They form biofilms on surfaces.
Answer: B
10. What is the term for substances that inhibit bacterial reproduction without killing
them?
A. Bactericidal
B. Antimicrobial
C. Bacteriostatic
D. Biocidal
Answer: C
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Here are the next 20 questions (11–30):
11. What is the disadvantage of alcohol as a disinfectant?
A. Not effective against bacterial spores.
B. It has a strong disagreeable odor.
C. Requires very high concentrations to work.
D. Ineffective against viruses with lipid envelopes.
Answer: A
12. Which heavy metal is commonly used in mouthwashes and antifungal paints?
A. Mercury
B. Copper
C. Zinc
D. Silver
Answer: C
13. What is the principle of action for halogens like iodine?
A. Lowering surface tension.
B. Denaturing proteins and dissolving lipids.
C. Oxidizing and halogenating cellular proteins.
D. Disrupting nucleic acids.
Answer: C
14. What is the main advantage of phenolics?
A. They are effective at low temperatures.
B. They remain active in the presence of organic matter.
C. They are non-toxic to human tissues.
D. They are effective against all spores.
Answer: B
15. Which of the following disinfectants is most effective against spores?
A. Alcohol
B. Glutaraldehyde
C. Phenol
D. Chlorine
Answer: B
16. Why are biofilms resistant to disinfectants?
A. They are composed of spores.
B. They are shielded by extracellular materials.
C. They only contain non-pathogenic microbes.
D. They are inactivated by chemical agents.
Answer: B
17. What is the function of quaternary ammonium compounds?
A. Sterilize surgical instruments.
B. Act as cationic detergents with germicidal activity.
C. Oxidize proteins in bacterial cells.
D. Penetrate spores and destroy nucleic acids.
Answer: B
18. What happens to disinfectant activity at very high temperatures?
A. It increases proportionally.
B. It decreases due to chemical degradation.
C. It becomes sporicidal.
D. It becomes highly toxic to humans.
Answer: B
19. What is the main reason for adding chlorine to drinking water?
A. To alter the pH of water.
B. To eliminate all organic compounds.
C. To form hypochlorous acid for microbial control.
D. To create biofilms for added protection.
Answer: C
20. Which of the following disinfectants is effective in gaseous form?
A. Hydrogen peroxide
B. Iodine
C. Ethylene oxide
D. Alcohol
Answer: C
21. Which chemical agent has oligodynamic action?
A. Ethylene oxide
B. Alcohol
C. Heavy metals
D. Quaternary ammonium compounds
Answer: C
22. What is the term for the initial cleaning of objects before disinfection?
A. Antisepsis
B. Pre-cleaning
C. Bioburden removal
D. Organic load reduction
Answer: B
23. Which factor affects the antimicrobial activity of glutaraldehyde?
A. Its pH and freshness.
B. The hardness of water.
C. The temperature of storage.
D. Its exposure to sunlight.
Answer: A
24. What is the main disadvantage of using phenol as a disinfectant?
A. Low antimicrobial activity.
B. Highly volatile and expensive.
C. Caustic effects on skin and systemic toxicity.
D. Ineffectiveness against lipid-containing bacteria.
Answer: C
25. What does water hardness interfere with during disinfection?
A. Germicidal activity of disinfectants.
B. Reduction of organic loads.
C. Oxidation of microbial proteins.
D. Inhibition of microbial biofilms.
Answer: A
26. What are aldehydes primarily used for?
A. Antiseptic hand scrubs.
B. Sterilizing medical tools and enclosed areas.
C. Disinfecting swimming pools.
D. Decontaminating drinking water.
Answer: B
27. What is the advantage of hydrogen peroxide as a disinfectant?
A. Effective against spores in open wounds.
B. Highly stable in light and heat.
C. Useful against anaerobic bacteria in wounds.
D. Inexpensive and non-toxic.
Answer: C
28. Why are bacterial endospores resistant to most disinfectants?
A. They lack a lipid membrane.
B. They are covered by a protective protein coat.
C. They have high enzymatic activity.
D. They are composed only of DNA.
Answer: B
29. What is the role of surface-active agents in microbial control?
A. Destroying enzymes of microbes.
B. Reducing water surface tension to disrupt membranes.
C. Oxidizing cellular contents.
D. Acting only against Gram-negative bacteria.
Answer: B
30. Why is ethylene oxide commonly used in sterilizing disposable medical equipment?
A. It is non-toxic to tissues.
B. It is effective at high temperatures.
C. It can penetrate plastic packaging.
D. It is inexpensive and easy to use.
Answer: C
Let me know if I should proceed with the next set of 70 questions!
Here are the next 30 questions (31–60):
31. What type of surface is easiest to disinfect effectively?
A. Rough and porous surfaces
B. Crevices and hinges
C. Smooth and hard surfaces
D. Grooved surfaces
Answer: C
32. What is the primary reason disinfectants must remain in contact with a surface for a
specific time?
A. To allow spores to germinate.
B. To ensure all pathogens are killed.
C. To allow drying of the chemical agent.
D. To neutralize organic loads.
Answer: B
33. What is the principle of action for heavy metals in disinfection?
A. Oxidizing lipids in membranes.
B. Combining with proteins to inactivate them.
C. Creating biofilms to inhibit pathogens.
D. Lowering surface tension in water.
Answer: B
34. What is the main disadvantage of using aldehydes like formaldehyde?
A. They are non-effective against spores.
B. They are highly irritating and carcinogenic.
C. They are unstable at room temperature.
D. They cannot penetrate plastic materials.
Answer: B
35. Which disinfectant is effective against lipid-containing viruses?
A. Phenolics
B. Quaternary ammonium compounds
C. Alcohol
D. All of the above
Answer: D
36. Which organisms are most resistant to chemical disinfectants?
A. Vegetative bacteria
B. Fungi
C. Mycobacteria
D. Bacterial endospores
Answer: D
37. What is the action of quaternary ammonium compounds on bacterial cells?
A. Destroying nucleic acids.
B. Disrupting the plasma membrane.
C. Oxidizing cellular proteins.
D. Creating biofilms to inhibit growth.
Answer: B
38. What are the two types of sterilization using chemical methods?
A. Liquid and gas sterilization
B. Organic and inorganic methods
C. Oxidation and reduction
D. High temperature and low temperature
Answer: A
39. Which of the following is an advantage of alcohol-based disinfectants?
A. Effective against bacterial spores.
B. Rapid action and low toxicity.
C. Active even in the presence of organic matter.
D. Long-lasting residual effect.
Answer: B
40. What chemical agent is added to swimming pools to control microbial growth?
A. Hydrogen peroxide
B. Chlorine
C. Alcohol
D. Silver nitrate
Answer: B
41. What is the major disadvantage of phenolics in disinfection?
A. They are ineffective at high pH levels.
B. They persist in the environment.
C. They are ineffective against spores.
D. They require prolonged contact time.
Answer: C
42. Which of the following best describes the role of antiseptics?
A. Destroying microbial spores on non-living objects.
B. Killing pathogens on living tissue.
C. Inhibiting the growth of microbes in drinking water.
D. Preventing microbial biofilm formation on surfaces.
Answer: B
43. What is the active antimicrobial component in Betadine?
A. Chlorhexidine
B. Phenol
C. Povidone-iodine
D. Ethylene oxide
Answer: C
44. What is the effect of increasing the pH on phenols?
A. Decreases their antimicrobial activity.
B. Increases their antimicrobial activity.
C. Makes them effective against spores.
D. Neutralizes their toxicity.
Answer: A
45. What is the mechanism of action of oxidizing agents like hydrogen peroxide?
A. Destroying proteins through alkylation.
B. Inhibiting DNA replication in bacteria.
C. Destroying lipids and structural proteins.
D. Oxidizing cellular components of microbes.
Answer: D
46. Which of the following disinfectants is effective in removing biofilms?
A. Alcohol
B. Aldehydes
C. Heavy metals
D. None of the above
Answer: D
47. Which chemical agent is commonly used in antifungal shampoos?
A. Zinc pyrithione
B. Copper sulfate
C. Mercury chloride
D. Benzalkonium chloride
Answer: A
48. What is the ideal concentration of ethanol for disinfection?
A. 40%
B. 50%
C. 70%–80%
D. 90%–100%
Answer: C
49. What is the advantage of using iodophors over tincture of iodine?
A. Iodophors are less irritating and don’t stain.
B. Iodophors are more sporicidal.
C. Iodophors have a shorter contact time.
D. Iodophors are more effective against viruses.
Answer: A
50. Why are aldehydes considered highly effective for disinfection?
A. They are effective at low concentrations.
B. They kill spores, viruses, and fungi.
C. They do not irritate living tissues.
D. They act within minutes of application.
Answer: B
51. Which chemical disinfectant is commonly used for preserving vaccines?
A. Zinc salts
B. Mercurial compounds
C. Ethylene oxide
D. Hydrogen peroxide
Answer: B
52. What type of disinfectant is used for sterilizing heat-sensitive medical equipment?
A. Hydrogen peroxide
B. Alcohol
C. Ethylene oxide gas
D. Heavy metals
Answer: C
53. Which antiseptic is commonly used in prescription mouthwashes?
A. Ethanol
B. Chlorhexidine
C. Benzalkonium chloride
D. Triclosan
Answer: B
54. What happens when a disinfectant solution ages?
A. Its potency increases.
B. Its effectiveness diminishes.
C. It becomes sporicidal.
D. It becomes more corrosive.
Answer: B
55. What is the role of organic matter in disinfection?
A. Enhances the action of disinfectants.
B. Interferes with the killing rate of microbes.
C. Increases the solubility of disinfectants.
D. Reduces microbial resistance.
Answer: B
56. Which of the following metals is used as an algicide?
A. Zinc
B. Copper
C. Mercury
D. Silver
Answer: B
57. What is the active component in most alcohol-based hand sanitizers?
A. Isopropanol
B. Ethylene oxide
C. Phenolics
D. Glutaraldehyde
Answer: A
58. Why is ethylene oxide considered hazardous?
A. It is highly flammable and toxic.
B. It cannot kill bacterial spores.
C. It is ineffective at low temperatures.
D. It reacts with water to form acids.
Answer: A
59. What is the main disadvantage of using hydrogen peroxide on wounds?
A. It is toxic to tissues.
B. It forms biofilms.
C. It is sporicidal.
D. It breaks down too quickly.
Answer: A
60. What is the role of quats in medical antiseptics?
A. Preserving tissues during surgery.
B. Sterilizing thermolabile drugs.
C. Cleaning and disinfecting skin.
D. Killing anaerobic bacteria in wounds.
Answer: C
Let me know if I should continue with the remaining 40 questions!
