Ch 5 Control of Microbial Growth

Cold and freezing are very effective in killing bacteria. True or False

False

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

False

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

False

Pasteurization results in the sterilization of food products. True or False

False

Prions are easily destroyed by common sterilization procedures. True or False

False

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

False

Boiling is very effective at removing most common waterborne pathogens. True or False

True

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

True

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

True

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

True

Upon heat treatment, bacteria die at a constant proportion. True or False

True

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

a) 6 minutes

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

a) Dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes

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

a) Endospores of Bacillus and Clostridium

Hexachlorophene has been particularly effective against a) Staphylococcus aureus. b) Micrococcus aureus. c) Escherichia coli. d) Enterobacter aerogenes. e) Streptococcus pneumoniae.

a) Staphylococcus aureus.

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.

a) cationic detergents that help wash surfaces.

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.

a) denature proteins and destroy cytoplasmic membranes.

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).

a) destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D processes (designed to kill 1012 endospores).

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.

a) irreversible denaturation of proteins.

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.

a) is very good for use on heat-sensitive medical items.

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.

a) is very useful for sterilizing heat- or moisture-sensitive items.

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.

a) producing reactive molecules such as superoxide and hydroxyl-free radicals.

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.

a) readily reacts with organics to produce potentially carcinogenic trihalomethanes.

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.

a) sterilization.

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.

a) the heat they generate in a product.

A suffix used to describe a killing action would be a) -static. b) -cidal. c) -cillin. d) -tion. e) -side.

b) -cidal.

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.

b) 121°C at 15 psi for 15 minutes.

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.

b) D-value - time to destroy 10% of microbes present.

Which would be most effective against Pseudomonas? a) Alcohol b) Radiation c) Quaternary ammonium compounds d) Iodophors e) Hand soap

b) Radiation

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.

b) They are acquired by susceptible people in the hospital.

A sterile item is free of a) microbes, viruses, AND prions. b) all viable microbes, endospores, AND viruses c) endospores, viruses, AND prions. d) microbes, endospores, AND prions. e) prions only.

b) all viable microbes, endospores, AND viruses

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.

b) can be used to either sterilize or pasteurize, depending on the dose of radiation.

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.

b) damaging nucleic acid.

Upon treatment with heat or chemicals, bacteria will a) all die immediately. b) die at a constant proportion. c) form endospores and survive. d) die at a geometric rate. e) always become resistant.

b) die at a constant proportion.

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.

b) enzymes from liquids.

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.

b) inhibit the germination of Clostridium botulinum endospores.

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.

b) is extensively used in antiseptics.

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.

b) membrane filtration.

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

c) Pasteurization

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).

c) Pseudomonas aeruginosa.

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)

c) Ultrahigh-temperature (UHT) method

One of the first chemicals used by Lister to prevent surgical infections was a) alcohol. b) iodine. c) carbolic acid. d) mercury. e) soap.

c) carbolic acid.

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.

c) heat-resistant endospores are unaffected.

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.

c) in a hot air oven.

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.

c) is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.

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.

c) prevent infection of second- and third-degree burns.

In a one D process, how many D values would it take to reduce a population of 10^10 cells to one survivor? a) 2 b) 4 c) 5 d) 10 e) 100

d) 10

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.

d) It is usually found as tinctures or iodophors.

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

d) non-enveloped viruses AND endospores.

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.

d) sterilize the inoculating loop.

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.

d) their use contributes to serious pollution of natural waters.

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.

e) All of the answer choices are correct.

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.

e) All of the answer choices are correct.

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.

e) All of the answer choices are correct.

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.

e) All of the answer choices are true.

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.

e) Bacterial resistance to some of the chemicals included to perishable products has been reported.

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.

e) It immediately kills all bacteria when applied to a wound.

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.

e) heat-sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus.