Practice Questions
Control 3: Evaluation and Other Factors

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1. As applied to microorganisms, the term "death" is most closely related to which of the following activities of microorganisms?
   
   1. reproduction.
   2. metabolism.
   3. nutrition.
   4. excretion.
   5. mutation.
   
   
   
2. Consider the ways in which the following antimicrobial chemicals are normally used. Which one is considered a STERILIZATION agent?
   
   1. gluteraldehyde
   2. copper sulfate
   3. ethanol
   4. silver nitrate
   5. iodine
   
   
   
3. You are bombarded every day with advertisements of antiseptics and disinfectants. It is important for you to know how they differ. Let us assume that you are working with a Streptococcus species in the lab. Your boss hands you an unknown chemical, and she says she wants to know whether a 1% solution left in contact with these cells for two minutes serves as an antiseptic or a disinfectant. IF THIS MATERIAL (at this concentration and exposure time) IS AN ANTISEPTIC, which one of the following results SHOULD YOU SEE AFTER REMOVING CELLS FROM THE CHEMICAL?
   
   1. A plate count after 2 min of exposure will be the same as the plate count just prior to exposure.
   2. A plate count after 2 min of exposure will be much less than the plate count just prior to exposure.
   3. The culture turbidity will drop drastically during the 2 min exposure.
   4. Microscopic examination of the culture after 2 min of exposure will show only viable endospores remaining.
   5. Counts taken with the counting chamber will show a drastic reduction in numbers during the 2 min exposure.
   
   
   
4. All of the following are antibiotic-producing microorganisms EXCEPT:
   
   1. Bacillus spp.
   2. Penicillium spp.
   3. Clostridium spp.
   4. Streptomyces spp.
   5. Micromonospora spp.
   
   
   
5. Many FACTORS affect CHEMICAL STERILIZATION or DISINFECTION. From the following list describing the effects of some of these factors, which one is NOT CORRECT?
   
   1. No one chemical can be bacteriostatic under one set of conditions and bactericidal under other conditions.
   2. The adverse effect is usually increased with heating.
   3. An antimicrobial chemical is usually more effective the more the pH differs from that which is optimum for growth of the microbe.
   4. The adverse effect is usually increased as exposure time increases.
   5. Permeation of the chemical into the cell varies with the age of culture and type of cell.
   
   
   
6. All of the following can be determined in the tube-dilution technique and the disk-plate method EXCEPT the:
   
   1. resistance or susceptibility of the bacterium to different antibiotics.
   2. antibiotics that will cause hypersensitivity reactions in an individual.
   3. antibiotics that have high antimicrobial activity against the microorganism.
   4. antibiotics that have low antimicrobial activity against the microorganism.
   5. antibiotics that have no antimicrobial activity against the microorganism.
   
   
   
7. A microbiology student conducted the tube-dilution method using a series of tubes containing sterile medium and various concentrations of a variety of antibiotics. The tubes were inoculated with a test bacterium. If penicillin G had a MIC of 25 g, erythromycin had a MIC of 50 g, and doxycycline had a MIC of 10 g, which of the following correctly ranks these antibiotics according to their antimicrobial activity against the bacterium, from highest activity to lowest?
   
   1. erythromycin, penicillin G, doxycycline
   2. erythromycin, doxycycline, penicillin G
   3. doxycycline, penicillin G, erythromycin
   4. doxycycline, erythromycin, penicillin G
   5. penicillin G, erythromycin, doxycycline
   
   
   
8. Which of the following statements about the AGAR-PLATE (KIRBY-BAUER) TECHNIQUE for measuring the effectiveness of antimicrobial chemicals is INCORRECT?
   
   1. Effectiveness of the chemical is usually determined within two hours after preparing the plate.
   2. Either Gram-positive or Gram-negative bacteria may be used as the test organism.
   3. The size of the inhibition zone helps determine the effectiveness of the chemical.
   4. This method can be used to test antibiotics, antiseptics, or disinfectants.
   5. Rate of diffusion may influence the size of the inhibition zone.
   
   
   
9. If you have an antimicrobial chemical that has a PHENOL COEFFICIENT of 25, then which of the following statements is TRUE?
   
   1. It can be diluted twenty-five times and still have the same killing effect as phenol.
   2. It will kill 25 times more bacteria than phenol.
   3. It will kill bacteria 25-times faster than phenol.
   4. It must be concentrated 25-times to have the same effect as phenol.
   5. It is 25-times less effective than phenol.
   
   
   
10. The PHENOL-COEFFICIENT method is a test that shows:
    
    1. the bactericidal affect of an unknown chemical compared with phenol.
    2. that phenol is the most effective antimicrobial chemical known.
    3. the antiseptic properties of phenol and an unknown antimicrobial chemical.
    4. the killing effect of phenol when tested at 5, 10, and 15 minutes.
    5. the rates of diffusion of phenol through agar compared with an unknown chemical.

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