Deck 7: The Control of Microbial Growth

Question 1

Which of the following chemical agents is used for sterilization?

A)alcohol
B)phenolics
C)ethylene oxide
D)chlorine
E)soap

Answer 1

C

Question 2

Disinfection of water is achieved by all of the following EXCEPT

A)ozone.
B)UV radiation.
C)chlorine.
D)copper sulfate.
E)peracetic acid.

Answer 2

E

Question 3

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.

Answer 3

E

Question 4

Which of the following disinfectants acts by disrupting the plasma membrane?

A)soaps
B)aldehydes
C)bisphenols
D)halogens
E)heavy metals

Question 5

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

Question 6

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.

Question 7

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.

Question 8

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.

Question 9

Which concentration of ethanol is the most effective bactericide?

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

Question 10

Oxidizing agents include all of the following EXCEPT

A)chlorine.
B)glutaraldehyde.
C)hydrogen peroxide.
D)iodine.
E)ozone.

Question 11

Which of the following does NOT achieve sterilization?

A)dry heat
B)pasteurization
C)autoclave
D)supercritical fluids
E)ethylene oxide

Question 12

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.

Question 13

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.

Question 14

Which of the following substances is used for surgical hand scrubs?

A)phenol
B)chlorine bleach
C)chlorhexidine
D)soap
E)glutaraldehyde

Question 15

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

Question 16

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

Question 17

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.

Question 18

The most effective form of chlorine is which of the following?

A)hypochlorous acid
B)hydrochloric acid
C)ozone
D)hypochlorite ion
E)chloromine

Question 19

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.

Question 20

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

Question 21

Which of the following pairs is mismatched?

A)ionizing radiation - hydroxyl radicals
B)ozone - takes electrons from substances
C)plasma sterilization - free radicals
D)supercritical fluids - CO₂
E)ultraviolet radiation - desiccation

Question 22

Table 7.3
The following data were obtained by incubating gram-positive bacteria in nutrient medium + disinfectant for 24 hours,then transferring one loopful to nutrient medium (subculturing).(+ = growth;- = no growth)

In Table 7.3,which disinfectant was bactericidal?

A)Doom
B)K)O.
C)Mortum
D)Sterl
E)The answer cannot be determined based on the information provided.

Question 23

Figure 7.2
Assume 10⁹ E.coli cells/ml are in a flask.

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

Question 24

Table 7.3
The following data were obtained by incubating gram-positive bacteria in nutrient medium + disinfectant for 24 hours,then transferring one loopful to nutrient medium (subculturing).(+ = growth;- = no growth)

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

A)Doom
B)K)O.
C)Mortum
D)Sterl
E)The answer cannot be determined based on the information provided.

Question 25

Table 7.1
A disk-diffusion test using Staphylococcus gave the following results:

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.

Question 26

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.
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

Question 27

All of the following are methods of food preservation EXCEPT

A)desiccation.
B)high pressure.
C)ionizing radiation.
D)microwaves.
E)osmotic pressure.

Question 28

Table 7.1
A disk-diffusion test using Staphylococcus gave the following results:

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.

Question 29

Table 7.1
A disk-diffusion test using Staphylococcus gave the following results:

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.

Question 30

All of the following are effective for destroying prions EXCEPT

A)boiling.
B)incineration.
C)NaOH + autoclaving at 134°C.
D)proteases.
E)None of the answers are correct;each of these will destroy prions.

Question 31

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.

Question 32

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

Question 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.

Question 34

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

Question 35

All of the following substances are used to preserve foods EXCEPT

A)biguanides.
B)nisin.
C)potassium sorbate.
D)sodium nitrite.
E)calcium propionate.

Question 36

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.
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.

Question 37

Ethylene oxide

A)is a good antiseptic.
B)is not sporicidal.
C)requires high heat to be effective.
D)is a sterilizing agent.
E)is the active chemical in household bleach.

Question 38

Table 7.3
The following data were obtained by incubating gram-positive bacteria in nutrient medium + disinfectant for 24 hours,then transferring one loopful to nutrient medium (subculturing).(+ = growth;- = no growth)

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

A)Doom
B)K)O.
C)Mortum
D)Sterl
E)The answer cannot be determined based on the information provided.

Question 39

Figure 7.2
Assume 10⁹ E.coli cells/ml are in a flask.

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

Question 40

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.
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.

Question 41

If you were preparing nutrient agar at home and did not have an autoclave,what could you use to sterilize the nutrient agar?

A)bleach
B)boiling for one hour
C)hydrogen peroxide
D)oven at 121°C for one hour
E)pressure cooker at 121°C for 15 minutes

Question 42

The most resistant of the bacterial endospores can withstand boiling for up to

A)10 min.
B)30 min.
C)1 hour.
D)5 hours.
E)20 hours.

Question 43

A kitchen countertop has a spill of vegetable oil that was wiped up but a film remains.What should be the next step in disinfecting this surface?

A)10% bleach
B)spray a disinfectant that contains a heavy metal
C)warm soapy scrub
D)isopropanol
E)chlorhexidine containing solution

Question 44

Pseudomonas has been found growing in quaternary ammonium compounds (quats).

Question 45

Desiccation is a reliable form of sterilization.

Question 46

Which chemical disinfectant can be considered a sterilizing liquid agent when appropriately applied?

A)quaternary ammonium compounds
B)70% ethanol
C)sodium benzoate
D)gluteraldehyde
E)ethylene oxide

Question 47

Any process that destroys the non-spore forming contaminants on inanimate objects is sterilization.

Question 48

Bone and tendons for transplant are decontaminated by

A)ethylene oxide.
B)glutaraldehyde.
C)peroxygens.
D)plasma sterilization.
E)supercritical fluids.

Question 49

One advantage of chemical plasma is that it ________ but a disadvantage is ________.

A)can be used to sterilize intricate surgical instruments such as a laproscope;cost
B)cost;difficulty of implementing the procedure
C)can be used for intricate surgical instruments;cannot be used on plastics
D)can be used on many materials;the need for high temperature is damaging to some equipment
E)destroys spores;cannot be used on plastics

Question 50

HEPA filters are effective because they are designed to remove all airborne particulates,including microorganisms down to

A)0)01 micrometers.
B)0)3 micrometers.
C)1 micrometer.
D)10 micrometers.
E)10 nanometers.

Question 51

Ultraviolet light (UV)causes irreversible breaks in DNA strands.

Question 52

Autoclaving is the most effective method of moist heat sterilization.

Question 53

Table 7.4
The results below were obtained from a use-dilution test of two disinfectants.Cultures were inoculated into tubes with varying concentrations of disinfectants and incubated for 24 hours at 20°C,then subcultured in nutrient media without disinfectants.
(+ = growth;- = no growth)

In Table 7.4,what is the minimal bacteriostatic concentration of each disinfectant? Which compound is bactericidal? At what concentration?

Question 54

Microorganisms placed in high concentrations of salts and sugars undergo lysis.

Question 55

The preservation of beef jerky from microbial growth relies on which method of microbial control?

A)filtration
B)lyophilization
C)desiccation
D)ionizing radiation
E)supercritical CO₂

Question 56

The thermal death time is the time needed to kill all the bacteria in a particular culture at a certain temperature.

Question 57

Which one of the following is known to be most resistant to quaternary ammonium compounds?

A)gram positive bacteria
B)members of the genus Pseudomonas
C)members of the genus Staphylococcus
D)fungi
E)enveloped viruses

Question 58

Moist heat destroys organisms by denaturing proteins.

Question 59

Some antimicrobial chemicals are considered to be disinfectants and antiseptics.

Question 60

The pH of the medium has no effect on the activity of the disinfectant being applied.

Question 61

Explain the set up and expected results of a use-dilution test for an endospore-producing Clostridium and a solution of chlorhexidine.

Question 62

What are the advantages of gluteraldehyde compared to formaldehyde?

Question 63

Assume that you are responsible for decontaminating materials in a large hospital.How would you sterilize each of the following? Briefly justify your answers.
a.a mattress used by a patient with bubonic plague
b.intravenous glucose-saline solutions
c.used disposable syringes
d.tissues taken from patients

Question 64

Why must most milk sold in the U.S.be refrigerated at all times while evaporated canned milk and milk in cardboard containers sold in Europe do not need to be refrigerated until they are opened?

Question 65

List the microbial targets of disinfecting chemicals and provide one example of a chemical agent that affects that structure.

Question 66

Table 7.5
The following results were obtained from a use-dilution test of two disinfectants.Cultures were inoculated into tubes containing varying concentrations of the disinfectants,incubated for 10 min.at 20°C,and then transferred to growth media without disinfectant.
(+ = growth;- = no growth)

In Table 7.5,which disinfectant is most effective? Against which group of bacteria is Disinfectant A most effective?

Question 67

How is hydrogen peroxide antimicrobial?