Deck 5: Control of Microbial Growth

Question 1

Lister developed his ideas on prevention of infection during medical procedures after studying the work of

A) Koch.
B) Pasteur.
C) Jenner.
D) Fleming.
E) Ehrlich.

Answer 1

B

Question 2

A suffix used to describe a killing action would be

A) -static.
B) -cidal.
C) -cillin.
D) -tion.
E) -side.

Answer 2

B

Question 3

In a one D process, how many D values would it take to reduce a population of 10¹⁰ cells to one survivor?

A) 2
B) 4
C) 5
D) 10
E) 100

Answer 3

D

Question 4

Pasteurization

A) is the use of heat to sterilize food products.
B) is a process that uses intense cold to kill microorganisms on foods.
C) is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.
D) is a process that uses short bursts of radiation to kill microorganisms on foods.
E) is a process used to preserve only milk and milk products.

Question 5

A common environmental organism that may even grow in certain chemical disinfectants is

A) Escherichia coli.
B) Streptococcus pneumoniae.
C) Pseudomonas aeruginosa.
D) Influenza virus (enveloped).
E) Adenoviruses (non-enveloped).

Question 6

Upon treatment with heat or chemicals, bacteria will

A) all die immediately.
B) die at a constant proportion.
C) die at an exponential rate.
D) die at a geometric rate.
E) always become resistant.

Question 7

One of the first chemicals used by Lister to prevent surgical infections was

A) alcohol.
B) iodine.
C) carbolic acid.
D) mercury.
E) soap.

Question 8

A sterile item is free of

A) microbes, viruses, AND prions.
B) microbes, endospores, AND viruses.
C) endospores, viruses, AND prions.
D) microbes, endospores, AND prions.
E) prions only.

Question 9

Which of the following are resistant to destruction by typical disinfection methods?

A) Endospores of Bacillus and Clostridium
B) Escherichia
C) Enveloped viruses
D) Mycoplasma species
E) Vegetative bacteria

Question 10

Hand washing with plain soap is very effective in controlling spread of microorganisms because

A) plain soap is bacteriostatic and inhibits bacterial growth.
B) it is very effective at the mechanical removal of microorganisms.
C) all soaps are virucidal and kill all viruses.
D) plain soap is bactericidal and kills all bacteria.
E) all soaps are bacteriostatic and kill endospores.

Question 11

Microbial death rates may be affected by

A) pH.
B) temperature.
C) the presence of organics.
D) growth in a biofilm.
E) All of the answer choices are correct.

Question 12

Which of the following is/are not (a) sterilization method(s)?

A) Hot air oven
B) Autoclave
C) Pasteurization
D) Filtration
E) Pasteurization AND autoclaving

Question 13

Boiling is not reliable for sterilization because

A) heat-sensitive instruments may be destroyed.
B) water boils at a higher temperature at lower altitudes.
C) heat-resistant endospores are unaffected.
D) viruses are more sensitive to heat than bacteria.
E) most pathogens are heat stable.

Question 14

Moist heat kills microorganisms by

A) irreversible denaturation of proteins.
B) destruction of carbohydrates in the cell wall.
C) denaturation of nucleic acids.
D) dissolving the capsule.
E) destruction of the nuclear envelope.

Question 15

Typical conditions used for sterilization are

A) 100°C for 10 minutes.
B) 121°C at 15 psi for 15 minutes.
C) 80°C for 15 minutes.
D) 72°C for 15 seconds.
E) 100°C for 10 seconds.

Question 16

The process of killing or removing all of the microorganisms in or on a material is called

A) sterilization.
B) disinfection.
C) sanitation.
D) antisepsis.
E) degerming.

Question 17

Which is True of nosocomial infections?

A) They are acquired by susceptible people at various social events.
B) They are acquired by susceptible people in the hospital.
C) They are acquired by susceptible people at sporting events.
D) They occur in communities but very seldom occur in hospitals.
E) They occur most frequently in isolated communities.

Question 18

To reduce or eliminate disease-/spoilage-causing organisms, food is often subjected to

A) heat.
B) chemical additives.
C) radiation.
D) cold.
E) All of the answer choices are correct.

Question 19

Which are essentially equivalent treatments?

A) Dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes
B) Dry 160°C heat for 1.0 hour; wet 200°C heat for 30 minutes
C) Dry 121°C heat for 1.5 hours; wet 200°C heat for 15 minutes
D) Dry 100°C heat for 2.0 hours; wet 100°C heat for 30 minutes
E) Dry 100°C heat for 30 minutes; wet 100°C heat for 30 minutes

Question 20

If a process kills 90% of the organisms per minute, how many minutes would it take to kill all organisms when starting with 100,000 organisms?

A) 6 minutes
B) 3 minutes
C) 2 minutes
D) 1 minute
E) 60 minutes

Question 21

Glutaraldehyde

A) is very good for use on heat-sensitive medical items.
B) inactivates lipids.
C) does not affect non-enveloped viruses.
D) is used in gaseous form.
E) kills bacteria but does not affect endospores.

Question 22

Commercial canning processes

A) destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D processes (designed to kill 10¹² endospores).
B) kill all endospores, are especially needed on acidic foods, AND are 12D processes (designed to kill 10¹² endospores).
C) are especially needed on low acid foods, are 12D processes (designed to kill 10¹² endospores), AND destroy E. coli endospores.
D) destroy E. coli endospores, are especially needed on acidic foods, AND are 12D (designed to kill 10¹² endospores) processes.
E) destroy Clostridium botulinum spores, are especially needed on very acidic foods, AND are 12D processes (designed to kill endospores in 12 days).

Question 23

Generally, membrane filters are not used to remove

A) bacteria from liquids.
B) enzymes from liquids.
C) microorganisms from gases.
D) spoilage agents from alcoholic beverages.
E) bacteria from nutrient broths.

Question 24

Gamma irradiation

A) has not been approved for use on food.
B) can be used to either sterilize or pasteurize, depending on the dose of radiation.
C) leaves some radioactive particles in the treated substance.
D) usually kills by generating heat and denaturing proteins. 
E) frequently causes a product to become carcinogenic.

Question 25

Chlorine

A) readily reacts with organics to produce potentially carcinogenic trihalomethanes.
B) is expensive but is able to destroy all types of microorganisms.
C) is unaffected by the presence of organic material.
D) is ineffective when diluted.
E) can be used effectively as an antiseptic.

Question 26

Alcohols are not reliably effective at destroying

A) vegetative bacteria AND endospores.
B) enveloped viruses AND endospores.
C) non-enveloped viruses AND enveloped viruses.
D) non-enveloped viruses AND endospores.
E) non-enveloped viruses AND vegetative cells

Question 27

Liquid media containing heat-sensitive components would best be sterilized by

A) ultraviolet (UV) light at 500 nm.
B) membrane filtration.
C) freezing.
D) lyophilization.
E) refrigeration.

Question 28

Gamma rays cause biological damage in living systems by

A) producing reactive molecules such as superoxide and hydroxyl-free radicals.
B) causing breakdown of ribosomes and peptidoglycan.
C) introducing life-threatening toxins.
D) making the substance radioactive.
E) causing a cell to multiply too fast for its environment.

Question 29

Which would be most effective against Pseudomonas?

A) Alcohol
B) Radiation
C) Quaternary ammonium compounds
D) Iodophors
E) Hand soap

Question 30

Chlorhexidine

A) is an aldehyde.
B) is extensively used in antiseptics.
C) is ineffective against vegetative bacteria.
D) is limited in use due to its high toxicity.
E) commonly causes adverse side effects.

Question 31

Oxidation of proteins is achieved most readily

A) by moist heat.
B) by moist heat under pressure.
C) in a hot air oven.
D) in the presence of organics.
E) in a refrigerator.

Question 32

The autoclave treatment may be monitored by

A) heat-sensitive tape AND pressure indicators.
B) heat-resistant endospores of Geobacillus stearothermophilus.
C) pressure indicators AND waiting for contaminants to appear on freshly poured media.
D) waiting for contaminants to appear on freshly poured media.
E) heat-sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus.

Question 33

Microwaves do not kill organisms directly but kill by

A) the heat they generate in a product.
B) generating free radicals.
C) generating toxins.
D) creating thymine dimers.
E) decreasing the pressure in the cells.

Question 34

Chemical germicides

A) may react irreversibly with proteins/enzymes.
B) may react with cytoplasmic membranes or viral envelopes.
C) may be disinfecting or even sterilizing.
D) are sensitive to dilution factor, time of contact, and temperature of use.
E) All of the answer choices are True.

Question 35

Which of the following methods sterilize the materials?

A) Pasteurization
B) High-temperature-short-time pasteurization (HTST)
C) Ultrahigh-temperature (UHT) method
D) Medium-temperature-intermediate-time pasteurization (MTIT)
E) Low-temperature-short-time pasteurization (LTST)

Question 36

Select the False statement regarding hydrogen peroxide.

A) It is a sterilant for inanimate objects and is quickly inactivated on living tissue.
B) It leaves no toxic residue and is safe on materials such as glass and plastic.
C) It is broken down by catalase into water and oxygen.
D) It is even more effective when used in combination with peracetic acid.
E) It immediately kills all bacteria when applied to a wound.

Question 37

A common application of dry heat in the microbiology laboratory is to

A) prepare specimens for study.
B) sterilize media.
C) sterilize plastics.
D) sterilize the inoculating loop.
E) sterilize Petri dishes.

Question 38

Ethylene oxide is gas that

A) is very useful for sterilizing heat- or moisture-sensitive items.
B) is harmless to people and is safe to use.
C) is used as a 37% aqueous solution.
D) destroys microbes excluding endospores and viruses.
E) reacts with nucleic acids in a cell.

Question 39

Ultraviolet radiation at the bactericidal wavelength destroys bacteria by

A) destroying endospores.
B) damaging nucleic acid.
C) preventing spore formation.
D) denaturing proteins.
E) disrupting ribosomes.

Question 40

Which is True of iodine?

A) It readily kills endospores.
B) It may be used as an antiseptic but not as a disinfectant.
C) It can be used at any dilution.
D) It is usually found as tinctures or iodophors.
E) It may be used as a disinfectant but not as an antiseptic.

Question 41

Boiling is very effective at removing most common waterborne pathogens.

Question 42

Organic acids, such as benzoic acid, are often added to foods to prevent microbial growth.

Question 43

Phenolics

A) denature proteins and destroy cytoplasmic membranes.
B) become ineffective in the presence of detergents or organic material.
C) such as triclosan have very limited commercial use.
D) reliably inactivate all groups of viruses.
E) are ineffective against Mycobacterium species.

Question 44

Compounds of tin, mercury, arsenic, and copper are no longer used to prevent microbial growth in cooling water primarily because

A) antibiotics are cheaper.
B) other chemicals were shown to be much more effective.
C) microbes developed resistance to these metals.
D) their use contributes to serious pollution of natural waters.
E) All of the answer choices are correct.

Question 45

Heat treatment is an effective method for sterilization or disinfection of all materials.

Question 46

Hydrogen peroxide may be used as a sterilant on living tissue.

Question 47

Pasteurization results in the sterilization of food products.

Question 48

Upon heat treatment, bacteria die at a constant proportion.

Question 49

Silver sulfadiazine, a combination of silver and a sulfa drug, is used to

A) disinfect water for drinking.
B) prevent infection of surgical wounds.
C) prevent infection of second- and third-degree burns.
D) counteract lead poisoning.
E) prevent ophthalmia neonatorum in babies.

Question 50

Quaternary ammonium compounds are

A) cationic detergents that help wash surfaces.
B) attracted to the positive charge on the microbial cell surface.
C) toxic and cannot be used on food preparation surfaces.
D) very effective against endospores and non-enveloped viruses
E) anionic detergents that help wash surfaces.

Question 51

Hexachlorophene has been particularly effective against

A) Staphylococcus aureus.
B) Micrococcus aureus.
C) Escherichia coli.
D) Enterobacter aerogenes.
E) Streptococcus pneumoniae.

Question 52

The more bacteria one starts with, the longer it will take to kill them all.

Question 53

Which of the following is (are) considered when selecting a germicidal chemical?

A) Toxicity AND cost
B) Cost AND compatibility with the material being treated
C) Compatibility with the material being treated AND environmental impact
D) Environmental impact, toxicity AND cost
E) All of the answer choices are correct.

Question 54

100% ethanol is twice as effective as 60% ethanol at controlling bacteria.

Question 55

Cold and freezing are very effective in killing bacteria.

Question 56

Generally, heavy metals, except silver, have been proven to be too toxic for use on human tissue and are no longer used medically.

Question 57

Dry heat takes a much shorter time to sterilize material than wet heat.

Question 58

The endospores of Pseudomonas make that organism very difficult to kill.

Question 59

The most important function of nitrites in processed foods is to

A) prevent browning.
B) inhibit the germination of Clostridium botulinum endospores.
C) prevent carcinogen formation.
D) make the food more acidic.
E) destroy cell membranes of potential pathogens.

Question 60

Prions are easily destroyed by common sterilization procedures.

Question 61

You tell Jasmine that it is important that she use a sterile instrument to pierce Paul's boil. Jasmine does not know what "sterile" means or why she needs to use something sterile for her "boil surgery," so you explain. Select the best answer.

A) A sterile instrument is free of all most pathogens but not environmental organisms. Jasmine needs to use a sterile blade because it will come into contact with Paul's tissues, and is thus a semi-critical instrument.
B) A sterile instrument is free of most microbes. Jasmine needs to use a sterile blade because it will come into contact with Paul's tissues, and is a critical instrument, although the risk for infection is low.
C) A sterile instrument comes in a sealed pack and is returned to that before its next use. Jasmine needs to use a sterile blade because it will come into contact with Paul's tissues, and is thus a critical instrument.
D) A sterile instrument is free of all microbes, endospores, and viruses. Jasmine needs to use a sterile blade because it will come into contact with Paul's tissues, and is thus a critical instrument.
E) The only known sterile instruments are hypodermic syringes, so Jasmine should use that to pop Paul's boil. Syringes are non-critical instruments because they make small wounds. 

Question 62

Which of the following statements is False regarding Giardia?

A) It contains 80S ribosomes.
B) It is aquatic.
C) It has a phospholipid cytoplasmic membrane.
D) It has a peptidoglycan cell wall.
E) It's DNA is contained within a membrane.

Question 63

At the end of your conversation with Jasmine, you tell her that the best course of action for her and Paul is to go to the clinic and have the boil treated there. A boil is a serious infection and the risks of trying to treat it at home are just too great.

Question 64

Your brother goes on to explain the concept of decimal reduction (D-value) time to you. To illustrate his point, he tells you that if the D-value for Giardia was 3 minutes and the starting number of cells was 10⁴, the time it would take to eliminate all of the Giardia cells would be

A) 15 minutes.
B) 3 minutes.
C) 10 minutes.
D) 9 minutes.
E) 12 minutes.

Question 65

You tell Jasmine that there are various ways that she can in fact sterilize the knife she plans to use. Which of the following is unlikely to be available to Jasmine for sterilizing her knife in her home?

A) Household bleach, used at a 1:100 dilution.
B) Heating the knife in a flame, such as that on a gas stove.
C) Irradiating the knife with gamma rays.
D) Cleaning the knife with rubbing alcohol from the pharmacy.
E) Heating the knife to a high temperature in the oven.

Question 66

Jasmine tells you she plans to wash her hands with soap and water before working on Paul's boil, to get rid of all the bacteria on her skin and prevent the possibility of Paul getting an infection. You tell her

A) that washing and scrubbing with soap will be fine because the soap will destroy absolutely all of the bacteria on Jasmine's hands. 
B) that washing and scrubbing with soap is generally sufficient to control microbes in routine situations but that soap itself does not destroy many organisms. Jasmine should try to get some sterile gloves.
C) the likely problem is not going to be the bacteria on Jasmine's hands but those on Paul's back. She doesn't need to wash her hands but she should wash Paul's back before she works on his boil.
D) that people who are shower regularly are clean and don't have any bacteria on them. Jasmine doesn't need to bother with trying to wash any bacteria off her hands because there won't be any if she showered that day.
E) that people have so many bacteria on their skin, it is impossible to remove them. Even washing with soap won't remove any bacteria because they exist in biofilms on the skin. You tell Jasmine that the bacteria are normal microbiota and are harmless.

Question 67

Please select the INCORRECTLY matched pair.

A) Bacterial endospores - highly resistant.
B) D-value - time to destroy 10% of microbes present.
C) Critical instrument - scalpels and needles.
D) Incineration - burns cells to ashes.
E) Sterilants - destroy all microbes including endospores and viruses.

Question 68

Please select the True statement regarding preservation of perishable products.

A) Nitrites and nitrates are always converted into carcinogens by intestinal bacteria.
B) Refrigeration destroys most pathogens and all spoilage microorganisms.
C) Salting and drying increase the availability of water in food above the limits required for growth of most microbes.
D) Drying stops microbial growth, and reliably kills all bacteria and fungi in or on foods.
E) Bacterial resistance to some of the chemicals included to perishable products has been reported.

Question 69

You ask your brother which method of eliminating microbes is the best in general. He tells you that there is no one perfect method and that various factors must be taken into account when considering any antimicrobial approach. These include all of the following EXCEPT 

A) the type of microbes to be controlled.
B) environmental conditions such as temperature.
C) whether a potential infection can be easily treated.
D) situational considerations (is a method practical for the situation?).
E) the number of microbes to be controlled.

Question 70

Your brother tells you that most likely you ingested Giardia cysts that were in the stream water. He says you should have treated the water before you drank it. Which of the following would NOT have been a possible way for you to do this, as a hiker? 

A) Boiling the water.
B) Using a portable hiker's filter.
C) Using commercial water-purifying tablets (iodine).
D) Using high pressure processing.
E) In fact, none of these would be possible for a hiker.