Deck 5: Control of Microbial Growth

Question 1

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.

Answer 1

B

Question 2

A sterile item is free of

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

Answer 2

E

Question 3

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

A)Escherichia coli.
B)Streptococcus pneumoniae.
C)Pseudomonas aeruginosa.
D)enveloped virus.

Answer 3

C

Question 4

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.

Question 5

Plain soap is very effective in controlling spread of microorganisms because it is

A)bacteriostatic.
B)very effective at the mechanical removal of microorganisms.
C)virucidal.
D)bactericidal.

Question 6

Nosocomial infections

A)are acquired at various social events.
B)are acquired while in the hospital.
C)occur because of a susceptible population and presence of disease causing organisms.
D)are acquired at sporting events.
E)are acquired while in the hospital AND occur because of a susceptible population and presence of disease causing organisms.

Question 7

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 choices are correct.

Question 8

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

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

Question 9

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

A)endospores of Bacillus and Clostridium
B)Pseudomonas
C)naked viruses
D)Mycobacterium spp.
E)All of the choices are correct.

Question 10

Boiling is not reliable for sterilization because

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

Question 11

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)1 minute
B)2 minutes
C)3 minutes
D)6 minutes

Question 12

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

Question 13

Microbial death rates may be affected by

A)pH.
B)temperature.
C)the presence of organics.
D)All of the choices are correct.

Question 14

In order to speed up the sterilization process, which of the following would be useful?

A)drying the material
B)washing/mechanical removal of bacteria/organic matter
C)addition of organics
D)nothing
E)washing/mechanical removal of bacteria/organic matter AND addition of organics

Question 15

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

Question 16

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

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

Question 17

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

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

Question 18

Moist heat kills microorganisms by

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

Question 19

A suffix used to describe a killing action would be

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

Question 20

Pasteurization

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

Question 21

Which would be most effective against Pseudomonas?

A)alcohol
B)radiation
C)quaternary ammonium compounds
D)iodophors

Question 22

Gamma rays cause biological damage in living systems by

A)producing reactive molecules such as superoxide and hydroxyl free radicals.
B)causing tiny gravity sinks and black holes to be formed in the substance.
C)introducing toxins.
D)making the substance radioactive.

Question 23

Which is true of iodine?

A)It does not readily kill endospores.
B)It may be used as an antiseptic or as a disinfectant.
C)It is important to use it at the recommended dilution.
D)It is usually found as tinctures or iodophors.
E)All of the choices are true.

Question 24

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 choices are true.

Question 25

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.

Question 26

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 disrupting cell membranes.

Question 27

Glutaraldehyde

A)is, if given enough time, able to destroy all forms of microbial life.
B)is very good for use on heat-sensitive medical items.
C)attacks lipids.
D)does not affect naked viruses.
E)is, if given enough time, able to destroy all forms of microbial life AND is very good for use on heat-sensitive medical items.

Question 28

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.

Question 29

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.

Question 30

Alcohols are not reliably effective at destroying

A)vegetative bacteria.
B)enveloped viruses.
C)naked viruses.
D)endospores.
E)naked viruses AND endospores.

Question 31

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

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

Question 32

Which of the following methods sterilize the materials?

A)Pasteurization
B)High-temperature-short-time pasteurization (HTST)
C)Ultrahigh-temperature (UHT) method
D)None of these are sterilization methods

Question 33

Chlorhexidine

A)is a member of the biguanides.
B)is extensively used in antiseptics.
C)is ineffective against vegetative bacteria.
D)is limited in use due to its high toxicity.
E)is a member of the biguanides AND is extensively used in antiseptics.

Question 34

Ethylene oxide is gas that

A)is very useful for sterilizing heat or moisture sensitive items.
B)is potentially carcinogenic.
C)is used as a 37% aqueous solution.
D)is effective against all microorganisms except endospores and viruses.
E)is very useful for sterilizing heat or moisture sensitive items AND is potentially carcinogenic.

Question 35

Chlorine

A)readily reacts with organics to produce potentially carcinogenic trihalomethanes.
B)is an effective, inexpensive, disinfectant able to destroy all types of microorganisms.
C)is unaffected by the presence of organic material.
D)is ineffective when diluted.
E)readily reacts with organics to produce potentially carcinogenic trihalomethanes AND is an effective, inexpensive, disinfectant able to destroy all types of microorganisms.

Question 36

Commercial canning processes

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

Question 37

Which of the following is not a sterilization method?

A)hot air oven
B)autoclave
C)pasteurization
D)filtration

Question 38

Generally, membrane filters are not used to remove

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

Question 39

Ultraviolet radiation at the bactericidal wavelength destroy bacteria by

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

Question 40

The autoclave treatment may be monitored by

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

Question 41

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.

Question 42

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

Question 43

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

Question 44

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

Question 45

Quaternary ammonium compounds are

A)cationic detergents which help wash surfaces.
B)attracted to the negative charge on the microbial cell surface.
C)used as a 37% aqueous solution.
D)very effective against Pseudomonas.
E)cationic detergents which help wash surfaces AND attracted to the negative charge on the microbial cell surface.

Question 46

Pasteurization results in the sterilization of food products.

Question 47

Cold and freezing are very effective in killing bacteria.

Question 48

Which of the following is true of hydrogen peroxide?

A)It is a sterilant for inanimate objects and is quickly inactivated on living tissue.
B)It leaves a toxic residue.
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 is a sterilant for inanimate objects and is quickly inactivated on living tissue; it is broken down by catalase into water and oxygen AND it is even more effective when used in combination with peracetic acid.

Question 49

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

Question 50

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 choices are correct.

Question 51

Phenolics

A)denature proteins and destroy cytoplasmic membranes.
B)remain effective in the presence of detergents or organic material.
C)such as triclosan, have been used widely in various lotions and soaps.
D)reliably inactivate all groups of viruses.
E)denature proteins and destroy cytoplasmic membranes, remain effective in the presence of detergents or organic material, AND phenolics such as triclosan, have been used widely in various lotions and soaps.

Question 52

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

Question 53

Boiling is very effective at removing most common waterborne pathogens.

Question 54

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)treat bites from werewolves.

Question 55

Prions and viroids are easily destroyed by common sterilization procedures.

Question 56

Hexachlorophene has been particularly effective against

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

Question 57

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

Question 58

Upon heat treatment, bacteria die at a constant proportion.

Question 59

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

Question 60

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

A)toxicity
B)cost
C)compatibility with the material being treated
D)environmental impact
E)All of the choices are correct.