Microbiology: An Introduction, 13e (Tortora et al.)
Chapter 7 The Control of Microbial Growth
7.1 Multiple-Choice Questions
1) Which of the following is the best method to sterilize heat-labile solutions?
A) dry heat
B) autoclave
C) membrane filtration
D) pasteurization
E) freezing
2) Which of the following best describes the pattern of microbial death?
A) The cells in a population die at a constant rate.
B) All the cells in a culture die at once.
C) Not all of the cells in a culture are killed.
D) The pattern varies depending on the antimicrobial agent.
E) The pattern varies depending on the species.
3) Which of the following chemical agents is used for sterilization?
A) alcohol
B) phenolics
C) ethylene oxide
D) chlorine
E) soap
4) Which of the following substances is used for surgical hand scrubs?
A) phenol
B) chlorine bleach
C) chlorhexidine
D) soap
E) glutaraldehyde
5) Which of the following pairs of terms is mismatched?
A) bacteriostatic – kills vegetative bacterial cells
B) germicide – kills microbes
C) virucide – inactivates viruses
D) sterilant – destroys all living microorganisms
E) fungicide – kills yeasts and molds
6) The most effective form of chlorine is which of the following?
A) hypochlorous acid
B) hydrochloric acid
C) ozone
D) hypochlorite ion
E) chloromine
7) Which of the following regarding antimicrobial control agents is FALSE?
A) Contaminating organic debris such as blood or sputum decrease effectiveness.
B) Some agents kill by denaturing microbial cell proteins.
C) Some agents affect microbial cell membranes by dissolving lipids.
D) Silver-impregnated dressings are used for treating antibiotic-resistant bacteria.
E) Alcohols effectively inactivate nonenveloped viruses by attacking lipids.
8) Which of the following does NOT achieve sterilization?
A) dry heat
B) pasteurization
C) autoclave
D) supercritical fluids
E) ethylene oxide
9) Which of the following is a limitation of the autoclave?
A) It requires an excessively long time to achieve sterilization.
B) It cannot inactivate viruses.
C) It cannot kill endospores.
D) It cannot be used with heat-labile materials.
E) It cannot be used with glassware.
10) An agent used to reduce the number of bacteria on a toilet would most accurately be called
a(n)
A) disinfectant.
B) antiseptic.
C) aseptic.
D) fungicide.
E) virucide.
11) Application of heat to living cells can result in all of the following EXCEPT
A) breaking of hydrogen bonds.
B) alteration of membrane permeability.
C) denaturation of enzymes.
D) decreased thermal death time.
E) damage to nucleic acids.
12) Which of the following disinfectants acts by disrupting the plasma membrane?
A) soaps
B) aldehydes
C) bisphenols
D) halogens
E) heavy metals
13) Oxidizing agents include all of the following EXCEPT
A) chlorine.
B) glutaraldehyde.
C) hydrogen peroxide.
D) iodine.
E) ozone.
14) Disinfection of water is achieved by all of the following EXCEPT
A) ozone.
B) UV radiation.
C) chlorine.
D) copper sulfate.
E) peracetic acid.
15) All of the following substances are effective against nonenveloped viruses EXCEPT
A) alcohol.
B) chlorine.
C) ethylene oxide.
D) ozone.
E) None of the answers is correct; all of these are equally effective against nonenveloped viruses.
16) Which of the following methods is used to preserve food by slowing the metabolic processes
of foodborne microbes?
A) lyophilization
B) nonionizing radiation
C) freezing
D) ionizing radiation
E) pasteurization
17) Which concentration of ethanol is the most effective bactericide?
A) 100 percent
B) 70 percent
C) 50 percent
D) 40 percent
E) 30 percent
18) All of the following factors contribute to hospital-acquired infections EXCEPT
A) some bacteria metabolize disinfectants.
B) gram-negative bacteria are often resistant to disinfectants.
C) invasive procedures can provide a portal of entry for bacteria.
D) bacteria may be present in commercial products such as mouthwash.
E) None of the answers is correct; all of these factors may contribute to hospital-acquired
infection.
19) Which of the following treatments is the most effective for controlling microbial growth?
A) 63°C for 30 minutes
B) 72°C for 15 seconds
C) 140°C for 4 seconds
D) They are equivalent treatments.
E) None of the answers is correct.
20) Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper?
A) autoclave
B) gamma radiation
C) microwaves
D) sunlight
E) ultraviolet radiation
21) Which of the following regarding antimicrobial control agents is FALSE?
A) Contaminating organic debris such as blood or sputum will decrease effectiveness.
B) Some agents kill by denaturing microbial cell proteins.
C) Some agents affect microbial cell membranes by dissolving lipids.
D) Some agents are utilized as both an antiseptic and a disinfectant.
E) Most chemical agents can achieve sterility.
Figure 7.1
A suspension of 106 Bacillus cereus endospores was put in a hot-air oven at 170°C. Plate counts
were used to determine the number of endospores surviving at the time intervals shown.
22) In Figure 7.1, what is the thermal death time?
A) 150°C
B) 60 minutes
C) 120 minutes
D) 100°C
E) The answer cannot be determined based on the information provided.
23) In Figure 7.1, the thermal death point for this culture is
A) 15 minutes.
B) 50°C.
C) 30 minutes.
D) 170°C.
E) The answer cannot be determined based on the information provided
24) In Figure 7.1, the decimal reduction time (D value) for the culture, which is defined as the
time to reduce a population by one log, is approximately
A) 0 minutes.
B) 10 minutes.
C) 30 minutes.
D) 40 minutes.
E) 60 minutes.
25) Which of the following results in lethal damage to nucleic acids?
A) heat
B) radiation
C) certain chemicals
D) heat and radiation
E) heat, radiation, and some chemicals
26) Which of the following pairs is mismatched?
A) Ag – wound dressings
B) biguanide – sporocide
C) CuSO4 – algicide
D) H2O2 – open wounds
E) organic acids – food preservation
Figure 7.2
Assume 109 E. coli cells/ml are in a flask.
27) Which graph in Figure 7.2 best depicts the effect of placing the culture in an autoclave for 15
minutes at time x?
A) a
B) b
C) c
D) d
E) e
28) Which graph in Figure 7.2 best depicts the effect of placing the culture at 7°C at
time x?
A) a
B) b
C) c
D) d
E) e
Table 7.1
A disk-diffusion test using Staphylococcus gave the following results:
Disinfectant Zone of inhibition (mm)
A 0
B 2.5
C 10
D 5
29) In Table 7.1, which compound was the most effective against Staphylococcus?
A) A
B) B
C) C
D) D
E) The answer cannot be determined based on the information provided.
30) In Table 7.1, which compound was the most effective against E. coli?
A) A
B) B
C) C
D) D
E) The answer cannot be determined based on the information provided.
31) In Table 7.1, which compound was bactericidal?
A) A
B) B
C) C
D) D
E) The answer cannot be determined based on the information provided.
32) Table 7.2
The fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without
preservatives, is shown below:
Bacteria/ml
Cider only 2.2
Cider with potassium sorbate 2.0
Cider with sodium benzoate 0.5
Cider with potassium sorbate + sodium benzoate 0
In Table 7.2, which preservative is most effective?
A) potassium sorbate
B) sodium benzoate
C) potassium sorbate + sodium benzoate
D) no preservative
33) An iodophor is a(n)
A) phenol.
B) agent that reduces oxygen.
C) quaternary ammonium compound.
D) form of formaldehyde.
E) iodine mixed with a surfactant.