Deck 7: The Control of Microbial Growth

Question 1

Which of these is not an oxidizing agent?

A) Ozone
B) Iodine
C) Hydrogen peroxide
D) Chlorine
E) None of the above

Answer 1

None of the above

Question 2

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper?

A) Ultraviolet radiation
B) Sunlight
C) Microwaves
D) Gamma radiation
E) None of the above

Answer 2

D

Question 3

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: $\begin{array}{lr}& \underline{\text { Bacteria/ml }}\\\text { Cider only } & 2.2 \\\text { Cider with potassium sorbate } & 2.0 \\\text { Sodium benzoate } & 0 \\\text { Sorbate + benzoate } & 0\end{array}$

-In Table 7.2, which preservative is most effective?

A) Benzoate
B) Sorbate
C) Sorbate + benzoate
D) No preservative

Answer 3

Benzoate

Question 4

Table 7.1
A disk- diffusion test using Staphylococcus gave the following results: $\begin{array}{cc}\underline{\text { Disinfectant }}&\underline{\text { Zone of inhibition (mm)} }\\\text { A } & 0 \\\text { B } & 2.5 \\\text { C } & 10 \\\text { D } & 5\end{array}$

-In Table 7.1, which compound was bactericidal?

A) A
B) B
C) C
D) D
E) Can't tell

Question 5

Which one of the following does not belong with the others?

A) Propylene oxide
B) Beta- propiolactone
C) Hydrogen peroxide
D) Glutaraldehyde
E) Ethylene oxide

Question 6

Which of the following is not a heavy metal?

A) Merthiolate
B) Chlorine
C) Mercurochrome
D) Copper sulfate
E) Silver nitrate

Question 7

Which one of the following is most useful for disinfecting medical instruments?

A) Quats
B) Benzoic acid
C) Phenol
D) Bisphenols
E) Chlorine

Question 8

Which of the following affects the elimination of bacteria from an object?

A) Number of bacteria present
B) Presence of organic matter
C) Temperature
D) pH
E) All of the above

Question 9

All of the following contribute to hospital- acquired infections except

A) Bacteria may be present in commercial products such as mouthwash.
B) Some bacteria metabolize disinfectants.
C) Gram- negative bacteria are often resistant to disinfectants.
D) Invasive procedures can provide a portal of entry for bacteria.
E) None of the above.

Question 10

Which one of the following is most resistant to chemical biocides?

A) Viruses with lipid envelopes
B) Protozoan cysts
C) Gram- positive bacteria
D) Mycobacteria
E) Gram- negative bacteria

Question 11

Figure 7.3
Assume 109 E. coli cells/ml are in a flask.

Which graph in Figure 7.3 best depicts the effect of placing the culture at 7°C at time x?

A) a
B) b
C) c
D) d
E) e

Question 12

Which of the following substances can sterilize?

A) Chlorine
B) Phenolics
C) Ethylene oxide
D) Alcohol
E) Soap

Question 13

Foods are preserved with all of the following except

A) Potassium sorbate.
B) Sodium propionate.
C) Sodium nitrite.
D) Biguanides.
E) Nisin.

Question 14

Which of these disinfectants acts by denaturing proteins?

A) Phenolics
B) Halogens
C) Alcohols
D) Aldehydes
E) All of the above

Question 15

The antimicrobial activity of chlorine is due to which of the following?

A) The formation of ozone
B) The formation of hypochlorous acid
C) The formation of free O
D) The formation of hydrochloric acid
E) Disruption of the plasma membrane

Question 16

Table 7.1
A disk- diffusion test using Staphylococcus gave the following results: $\begin{array}{cc} \underline{\text { Disinfectant }}& \underline{\text { Zone of inhibition (mm) }}\\\text { A } & 0 \\\text { B } & 2.5 \\\text { C } & 10 \\\text { D } & 5\end{array}$

-In Table 7.1, which compound was the most effective against Staphylococcus?

A) A
B) B
C) C
D) D
E) Can't tell

Question 17

Which of the following best describes the pattern of microbial death?

A) The pattern varies depending on the species.
B) The pattern varies depending on the antimicrobial agent.
C) The cells in a population die at a constant rate.
D) All of the cells in a culture are never killed.
E) All the cells in a culture die at once.

Question 18

Which of the following is used for surgical hand scrubs?

A) Soap
B) Phenol
C) Glutaraldehyde
D) Chlorine bleach
E) Chlorhexidine

Question 19

Which of the following is not used for the disinfection of water?

A) Copper sulfate
B) Gamma radiation
C) Chlorine
D) Ozone
E) None of the above

Question 20

Table 7.1
A disk- diffusion test using Staphylococcus gave the following results: $\begin{array}{cc} \underline{\text { Disinfectant }}& \underline{\text { Zone of inhibition (mm) }}\\\text { A } & 0 \\\text { B } & 2.5 \\\text { C } & 10 \\\text { D } & 5\end{array}$

-In Table 7.1, which compound was the most effective against E. coli?

A) A
B) B
C) C
D) D
E) Can't tell

Question 21

Which of the following is a limitation of the autoclave?

A) Length of time
B) Ability to kill endospores
C) Ability to inactivate viruses
D) Use with glassware
E) Use with heat- labile materials

Question 22

Which of the following pairs is not correctly matched?

A) Merthiolate - open wounds
B) Ag - burns
C) CuSO₄ - algicide
D) H₂O₂ - open wounds
E) None of the above

Question 23

Figure 7.1

In Figure 7.1, what is the thermal death time for culture a?

A) 150°C
B) 60 min.
C) 100°C
D) 120 min.
E) Can't tell

Question 24

Figure 7.3
Assume 109 E. coli cells/ml are in a flask.

Which graph in Figure 7.3 best depicts the effect of placing the culture in an autoclave for 15 min. at time x?

A) a
B) b
C) c
D) d
E) e

Question 25

Which of the following treatments is the most effective for controlling microbial growth?

A) 140°C for < 1 sec.
B) 63°C for 30 min.
C) 72°C for 15 sec.
D) They are equivalent treatments.
E) None are effective.

Question 26

Bacterial death will result from damage to which of the following structures?

A) Proteins
B) Cell wall
C) Nucleic acids
D) Plasma membrane
E) All of the above

Question 27

Table 7.3
The following data were obtained by incubating the bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing.) $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Doom }} \quad \quad\quad\quad\quad\quad\quad\underline{K O}$
$\begin{array}{rrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & + & + & + \\1: 32 & - & + & + & + \\1: 64 & - & + & + & + \\1: 128 & + & + & + & +\end{array}$

$\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Mortum } }\quad\quad\quad\quad\quad\quad \underline{\text { Sterl }}$
$\begin{array}{rrrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & - & - & + \\1: 32 & - & + & + & + \\1: 64 & + & + & + & + \\1: 128 & + & + & + & +\end{array}$

-In Table 7.3, which disinfectant is the most effective at stopping bacterial growth?

A) Doom
B) K.O.
C) Mortum
D) Sterl
E) Can't tell

Question 28

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

A) Pasteurization
B) Dry heat
C) Autoclave
D) Membrane filtration
E) None of the above

Question 29

Glutaraldehyde is considered one of the most effective disinfectants for hospital use. Which of the following would not be true about glutaraldehyde?

A) Safe to transport.
B) Stains and corrodes.
C) Attacks all microorganisms.
D) Acts rapidly.
E) Not hampered by organic material.

Question 30

Table 7.3
The following data were obtained by incubating the bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing.) $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Doom }} \quad \quad\quad\quad\quad\quad\quad\underline{K O}$
$\begin{array}{rrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & + & + & + \\1: 32 & - & + & + & + \\1: 64 & - & + & + & + \\1: 128 & + & + & + & +\end{array}$

$\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Mortum }} \quad\quad\quad\quad\quad\quad \underline{\text { Sterl }}$
$\begin{array}{rrrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & - & - & + \\1: 32 & - & + & + & + \\1: 64 & + & + & + & + \\1: 128 & + & + & + & +\end{array}$

-In Table 7.3, which disinfectant was most effective against Salmonella?

A) Doom
B) K.O.
C) Mortum
D) Sterl
E) Can't tell

Question 31

Figure 7.2
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.

In Figure 7.2, the thermal death time for this culture is

A) 0 min.
B) 40 min.
C) 20 min.
D) 10 min.
E) 60 min.

Question 32

Which of the following is not effective against nonenveloped viruses?

A) Ozone
B) Alcohol
C) Chlorine
D) Ethylene oxide
E) All are equally effective

Question 33

Place the following surfactants in order from the most effective to the least effective antimicrobial a 1- Soap; 2- Anionic detergent; 3- Cationic detergent.

A) 1, 3, 2
B) 3, 1, 2
C) 2, 1, 3
D) 3, 2, 1
E) 1, 2, 3

Question 34

Which of the following does not achieve sterilization?

A) Ethylene oxide
B) Autoclave
C) Dry heat
D) Formaldehyde
E) Pasteurization

Question 35

Which of the following treatments does not yield a sterile product?

A) Gamma radiation
B) Autoclaving
C) 0.45 µm filtration
D) 170°C for 2 hr
E) Ionizing radiation

Question 36

Phenolics differ from phenol in that phenolics are all of the following except

A) More toxic to human cells.
B) More effective antibacterial agents.
C) Relatively odorless.
D) Nonirritating.
E) All of the above.

Question 37

Figure 7.2
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.

In Figure 7.2, the thermal death point for this culture is

A) 50°C.
B) 30 min.
C) 170°C.
D) 15 min.
E) Can't tell from the data provided.

Question 38

Figure 7.2
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.

In Figure 7.2, the decimal reduction time (D value) for the culture is approximately

A) 15 min.
B) 0 min.
C) 45 min.
D) 30 min.
E) 60 min.

Question 39

Figure 7.1

Assume that one culture is a freshly opened package of dried yeast with 0.1% moisture, another culture is the same yeast with 7.5% moisture, and the third culture is a package of yeast mixed with water. Each culture was exposed to 130°C in a hot- air oven. Which graph in Figure 7.1 most likely shows the yeast with 0.1% moisture?

A) a
B) b
C) c
D) a and b
E) b and c

Question 40

Iodophors differ from iodine (I2) in that iodophors

A) Are combined with a nonionic detergent.
B) Are longer lasting.
C) Don't stain.
D) Are less irritating.
E) All of the above.

Question 41

Table 7.3
The following data were obtained by incubating the bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing.) $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Doom} } \quad \quad\quad\quad\quad\quad\quad\underline{K O}$
$\begin{array}{rrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & + & + & + \\1: 32 & - & + & + & + \\1: 64 & - & + & + & + \\1: 128 & + & + & + & +\end{array}$

$\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Mortum }} \quad\quad\quad\quad\quad\quad \underline{\text { Sterl }}$
$\begin{array}{rrrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & - & - & + \\1: 32 & - & + & + & + \\1: 64 & + & + & + & + \\1: 128 & + & + & + & +\end{array}$

-In Table 7.3, which disinfectant was bactericidal?

A) Doom
B) K.O.
C) Mortum
D) Sterl
E) Can't tell

Question 42

Which concentration of ethyl alcohol is the most effective bactericide?

A) 30%
B) 70%
C) 40%
D) 50%
E) 100%

Question 43

Which of the following is not a direct result of heat?

A) Denaturing enzymes
B) Breaking hydrogen bonds
C) Breaking sulfhydryl bonds
D) Cell lysis
E) None of the above

Question 44

Which of the following substances is the least effective antimicrobial agent?

A) Cationic detergents
B) Phenolics
C) Iodine
D) Soap
E) Alcohol

Question 45

Which one of the following does not belong with the others?

A) Commercial sterilization
B) Sorbic acid
C) Benzoic acid
D) Pasteurization
E) Acid- anionic detergents