250+ TOP MCQs on Chemical Agents – Major Groups of Antimicrobial Agents and Answers

Microbiology Multiple Choice Questions on “Chemical Agents – Major Groups of Antimicrobial Agents”.

1. How much percentage of the aqueous solution of phenol rapidly kills the vegetative cells of microorganisms?
A. 1%
B. 2%
C. 5%
D. 10%
Answer: C
Clarification: Phenol is a very effective disinfectant. A 5% aqueous solution of phenol rapidly kills the vegetative cells of microorganisms; spores are much more resistant.

2. The antimicrobial activity of phenolics is not reduced at which of the following conditions?
A. acidic pH
B. alkaline pH
C. low temperatures
D. presence of soap
Answer: D
Clarification: The antimicrobial activity of phenolics is reduced at an alakaline pH and by organic material. Low temperatures and the presence of soap also reduce antimicrobial activity.

3. Alcohol concentrations above 60% are effective against _________________
A. bacteria
B. fungi
C. germs
D. viruses
Answer: D
Clarification: Alcohol concentrations above 60% are effective against viruses; however the effectiveness is influenced considerably by the amount of extraneous protein material in the mixture. The extraneous protein reacts with the alcohol and thus protects the virus.

4. Polyvinylpyrrolidone (PVP) is a complex belonging to which group?
A. Phenolic compounds
B. Iodophors
C. Metals
D. Aldehyde
Answer: B
Clarification: Polyvinylpyrrolidone (PVP) is a complex belonging to iodophors. Iodophors are mixtures of iodine with surface-active agents which act as carriers and solubilizers for the iodine. They possess the germicidal characteristics of iodine.

5. Which of the following agents irreversibly oxidize and inactivate proteins with sulphydral groups?
A. Alcohol
B. Phenol
C. Iodine
D. Chlorine
Answer: C
Clarification: Iodine is an oxidizing agent and oxidizing agents can irreversibly oxidize and thus inactivate essential metabolic compounds such as proteins with sulphydral groups.

6. Chlorinated lime is the alternative name for __________________
A. Calcium hypochlorite
B. Sodium hypochlorite
C. Chloramine-T
D. Azochloramide
Answer: A
Clarification: Calcium hypochlorite, Ca(OCl)2 is also known as chlorinated lime and it acts as an effective disinfectant like free chlorine.

7. Chloramines are more stable than than hypochlorites.
A. True
B. False
Answer: A
Clarification: One of the advantages of chloramines is stability; they are more stable than the hypochlorites in terms of prolonged release of chlorine.

8. Solutions of sodium hypochlorite of a 1% concentration are used for ________
A. sanitizing dairy equipment
B. personal hygiene and a household disinfectant
C. household bleaches
D. disinfecting open wounds
Answer: B
Clarification: Solutions of sodium hypochlorite of a 1% concentration are used for personal hygiene and as a household disinfectant and higher concentrations of 5-12% are also employed as household bleaches.

9. Which among the following is an example of an organic compound of mercury?
A. Mercuric chloride
B. Mercuric oxide
C. Mercurochrome
D. Ammoniated mercury
Answer: C
Clarification: Mercurochrome is an organic compound of mercury which are less irritating and less toxic than the inorganic mercury compounds. They are employed as antiseptics on cutaneous and mucosal surfaces.

10. Which of the following agents cause death to the cell by coagulation of cytoplasmic proteins?
A. Alcohol
B. Dyes
C. Chlorine
D. Heavy metals
Answer: D
Clarification: High concentration of salts of heavy metals like mercury, silver, and copper coagulate cytoplasmic proteins resulting in damage or death to the cell. Salts of heavy metals are also precipitants and in high concentrations they cause the death of cells.

11. Gram-negative organisms are more susceptible to higher concentrations of triphenylmethane dyes.
A. True
B. False
Answer: A
Clarification: Gram-positive organisms are more susceptible to lower concentrations of triphenylmethane dyes than are Gram-negative ones.

12. Which of the following is an acridine dye?
A. crystal violet
B. malachite green
C. tryptoflavine
D. brilliant green
Answer: C
Clarification: Two examples of dyes derived from acridine are acriflavine and tryptoflavine. These compounds exhibit selective inhibition against bacteria, particularly staphylococci and gonococci.

13. Gonococci are inhibited by tryptoflavine in dilutions of ____________
A. 1:200,000
B. 1:300,000
C. 1:1,000,000
D. 1:10,000,000
Answer: D
Clarification: Gonococci are inhibited by tryptoflavine in dilutions of 1:10,000,000 to 1:50,000,000. They possess little, if any, antifungal activity.

14. Ceepryn belongs to which of the following categories?
A. Anionic detergents
B. Cationic detergents
C. Nonionic detergents
D. Ammonium salts
Answer: B
Clarification: Those which ionize with the detergent property resident in the cation are referred as cationic detergents. An example of this is Ceepryn which is Cetylpyridinium chloride.

15. Which of the following agents are used as a preservative in ophthalmic solutions?
A. alcohol
B. quaternary ammonium salts
C. phenol
D. aldehydes
Answer:b
Clarification: The combined properties of germicidal activity and low toxicity, high solubility in water, stability in solution, and non-corrosiveness have resulted in many applications of quaternities as disinfectants and sanitizing agents. They are used as skin disinfectants, as a preservative of ophthalmic solutions, etc.

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