chapter five: control of microbial growth
bacteriostatic
Prevents the growth of bacteria, but does not kill them.
aseptic technique
Procedures that help prevent the accidental introduction of unwanted microbes.
bactericide
Substance that kills bacteria.
Which of the following is false? a) A high-level disinfectant cannot be used as a sterilant. b) Critical items must be sterilized before use. c) Low numbers of endospores may remain on semicritical items. d) Standard sterilization procedures do not destroy prions. e) Quaternary ammonium compounds can be used to disinfect food preparation surfaces.
a high-level disinfectant cannot be used as a sterilant
chlorhexidine is reliably a) microbistatic b) sporicidal c) bactericidal d) viricidal
bactericidal
True or False: with respect to drinking water treatment, traditional disinfectant procedures are able to destroy all known pathogens that cause diarrhea
false
Unlike a disinfectant, an antiseptic a) sanitizes objects rather than sterilizes them. b) destroys all microorganisms. c) is non-toxic enough to be used on human skin. d) requires heat to be effective. e) can be used in food products.
is non-toxic enough to be used on human skin
soap generally does not destroy most microbes, but it aids in their ______. a) dessication b) mechanical removal c) inhibition d) chemical removal
mechanical removal
a ______ instrument is one that should only come into contact with intact skin
non-critical
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
non-enveloped viruses AND endospores
when selecting an appropriate chemical disinfectant, it is important to realize that the death rate is significantly influenced by ______. (choose all that apply) a) pH b) time c) temperature
pH temperature
a brief heat treatment used to make foods and beverages safe for consumption is a) disinfection b) decontamination c) pasteurization
pasteurization
heat treatment, irradiation, and filtration are examples of ______ used to control microorganisms. a) physical processes b) chemical processes
physical processes
When filtering a liquid, it is a bad idea to use a membrane with a pore size smaller than necessary because a) filters with a smaller pore size might break more easily than those with large pores. b) filters with smaller pore sizes are electrically charged, which affects their efficiency. c) the smaller the pore size, the slower the filtration process, so you would be wasting time. d) you might inadvertently also remove hormones and growth factors from the filtered liquid. e) filters with small pores sizes are less effective than those with large pores at removing microbes.
the smaller the pore size, the slower the filtration process, so you would be wasting time
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.
their use contributes to serious pollution of natural waters
True or False: the more bacteria present on or in something, the longer it takes to kill them all
true
True or False: the risk of developing a fatal infection after surgery has substantially decreased since the late 19th century because modern hospitals now have procedures in place to avoid microbial contamination
true
True or False: tinctures of certain antimicrobial chemicals can be more effective than the same chemical in an aqueous solution
true
Aseptically boxed juices and cream containers are processed using which of the following heating methods? a) Commercial canning b) High-temperature-short-time (HTST) method c) Autoclaving d) Ultra-high-temperature (UHT) method e) Boiling
ultra-high-temperature (UHT) method
Which of the following is a method of choice for achieving a sufficient level of microbial control in routine day to day situations? a) Washing and scrubbing with soaps and detergents. b) Treatment of any materials both before and after they come into contact with human tissues. c) Sterilization of tools/instruments that come into contact with human tissues. d) Boiling all items that come into contact with intact skin. e )Irradiation of all products to sterilize them prior to use.
washing and scrubbing with soaps and detergents
In a one D process, how many D values would it take to reduce a population of 10^10 cells to one survivor? a) 100 b) 10 c) 2 d) 5 e) 4
10
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
6 minutes
aqueous solutions of alcohol at a concentration of ______ are more effective than 100% alcohol. a) 20-40% b) 10-30% c) 60-80% d) 40-50%
60-80%
Which concentration of alcohol is the most effective germicide? a) 100% b) 75% c) 50% d) 25% e) 5%
75%
disinfectant
A chemical that destroys many, but not all, microbes.
nitrates and nitrites are added to processed meats to prevent the germination of ______ endospores. a) Clostridium tetani b) Bacillus anthracis c) Bacillus cereus d) Clostridium botulinum
Clostridium botulinum
The decimal reduction time is the time it takes to kill 90% of a given bacterial population under certain conditions. If 90% of a population of 100,000 bacteria is killed in 10 minutes, how long would it take to reduce the population to 10 cells? a) 40 minutes b) 5 minutes c) 20 minutes d) 4 minutes e) 10 minutes f) 1,000 minutes
40 minutes
The D value is defined as the time it takes to kill a) all bacteria in a population. b) all pathogens in a population. c) 99.9% of bacteria in a population. d) 90% of bacteria in a population. e) 10% of bacteria in a population.
90% of bacteria in a population
antiseptic
A disinfectant nontoxic enough to be used on skin.
Which of the following is the most resistant to destruction by chemicals and heat? a) Bacterial endospores b) Fungal spores c) Mycobacterium tuberculosis d) E. coli e) HIV
bacterial endospores
which microbial agent is the most resistant to chemical control methods? a) protozoan cysts b) bacterial endospores c) non-enveloped viruses d) fungal spores
bacterial endospores
a common dry heat sterilization method used in the microbiology laboratory is a) flaming the inoculating loop b) heating agar in boiling water c) autoclaving used culture tubes
flaming the inoculating loop
Which of the following chemicals is/are suspected carcinogens? (choose all that apply) a) Formaldehyde b) Chlorhexidine c) Ethylene oxide d) Silver e) Nitrate and nitrite
formaldehyde ethylene oxide
phenolics are a) germicidal b) bacteriostatic c) sporicidal
germicidal
Which of the following can be used to make drinking water safe? (choose all that apply) a) aldehydes b) metals c) halogens d) alcohols e) biguanides f) phenolics g) ozone h) peroxygens
halogens ozone
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.
is very useful for sterilizing heat- or moisture-sensitive items
Select the statements about ionizing radiation that are true. (choose all that apply) a) it can be used to reduce spoilage organisms on food b) it may cause changes that make food carcinogenic c) it can be used to sterilize medications d) it causes food to become toxic e) it can be used to sterilize medical equipment f) it causes food to become radioactive
it can be used to reduce spoilage organisms on food it can be used to sterilize medications it can be used to sterilize medical equipment
Boiling is not a reliable method for sterilization because a) it releases toxic substances from water b) it does not destroy heat-resistant endospores c) water boils at different temperatures at different altitudes d) it causes the release of toxins from endospores
it does not destroy heat-resistant endospores
pasteurization
Brief heat treatment that reduces the number of spoilage organisms and destroys disease-causing microbes
sterile
Free of all viable microbes, including endospores and viruses.
preservation
Inhibition of microbial growth to delay spoilage.
sterilization
The destruction or removal of all microbes through physical or chemical means.
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.
all of the answer choices are correct
chlorhexidine solutions are commonly used for... (choose all that apply) a) antisepsis of skin and skin wound care b) mouthwashes c) disinfecting food preparation equipment d) disinfecting drinking water
antisepsis of skin and skin wound care mouthwashes
aqueous solutions of ethyl or isopropyl alcohol are commonly used at antiseptics and disinfectants because they... (choose all that apply) a) are relatively inexpensive b) quickly kill vegetative bacteria and fungi c) evaporate quickly d) do not leave a residue e) are relatively non-toxic f) quickly destroy endospores
are relatively inexpensive quickly kill vegetative bacteria and fungi do not leave a residue are relatively non-toxic
Select the correct statements about autoclaving. (choose all that apply) a) biological indicators such as heat-resistant endospores are used to ensure that an autoclave is working properly b) autoclaving is consistently effective in sterilizing most objects c) autoclave tape is used to ensure that an object has been effectively sterilized d) autoclaving involves the use of both temperature and pressure e) the pressure used in autoclaving plays a direct role in killing microbes f) adding pressure to the autoclave increases the temperature of the steam in it g) autoclaving was pioneered by Louis Pasteur and is used to preserve food h) a tightly closed container can be effectively sterilized by autoclaving
biological indicators such as heat-resistant endospores are used to ensure that an autoclave is working properly autoclaving is consistently effective in sterilizing most objects autoclaving involves the use of both temperature and pressure adding pressure to the autoclave increases the temperature of the steam in it
All of the following could be used to sterilize an item except a) boiling. b) incineration. c) irradiation. d) sporocides. e) filtration.
boiling
adding sorbic, propionic, and benzoic acid to foods affects ______ of microbes. a) nucleus structure b) cell membrane function c) ribosomes d) cell wall function
cell membrane function
disinfection by-products (DBPs)
compounds formed when chlorine or other disinfectants react with natural chemicals in water
Which of the following concerns would lead a user to wash an item after it had been treated with a germicide? a) Storage and stability. b) Toxicity to the environment. c) Presence of organic matter. d) Corrosive residue left after treatment. e) Cost and availability.
corrosive residue left after treatment
Ultraviolet light kills bacteria by a) generating heat. b) damaging DNA. c) inhibiting protein synthesis. d) damaging cell walls. e) damaging cytoplasmic membranes.
damaging dna
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.
damaging nucleic acid
treating a surface by washing or using disinfectants in order to reduce the number of pathogens on that surface to a safe level is called ______.
decontamination
Choose which of the following best describe the difference between a disinfectant and an antiseptic. a) Disinfectants are chemicals that completely destroys all microbes on a product. Antiseptics are chemicals that reduce the number of microbes on a product. b) Disinfectants are chemicals that reduce the number of pathogenic microbes on an inanimate surface or object. Antiseptics are chemicals used to delay the spoilage of food or other perishable materials by slowing the growth of microorganisms. c) Disinfectants and antiseptics are both types of chemicals used to remove microbes from any kind of surface. They are used interchangeably. d) Disinfectants are antimicrobial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. Antiseptics are antimicrobial chemicals that can be used on skin or tissues to achieve the same result. e) Disinfectants are chemicals that reduce the number of microbes to meet accepted health standards. Antiseptics are chemicals that completely eliminate of all microbes/viruses from a surface.
disinfectants are antimicrobial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. antiseptics are antimicrobial chemicals that can be used on skin or tissues to achieve the same result
the process that eliminates most or all pathogens on or in a material is a) decontamination b) disinfection c) sterilization
disinfection
Commercial canning processes are designed to ensure destruction of which of the following? a) All vegetative bacteria b) All viruses c) Endospores of Clostridium botulinum d) E. coli e) Mycobacterium tuberculosis
endospores of Clostridium botulinum
All of the following are routinely used to preserve foods except a) high concentrations of sugar. b) high concentrations of salt. c) benzoic acid. d) freezing. e) ethylene oxide.
ethylene oxide
True or False: 100% ethanol is twice as effective as 60% ethanol at controlling bacteria.
false
True or False: HIV is highly resistant to antimicrobial chemicals and requires lengthy exposure to these products in order to be destroyed
false
True or False: Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature.
false
True or False: Sterilization is the destruction of all living microbes from a surface by physical or chemical means.
false
salting and drying decrease the availability of water in food, resulting in an environment that is ______ relative to microbes, thereby preventing their growth. a) isotonic b) hypotonic c) hypertonic
hypertonic
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.
in a hot air oven
what are the effects of increasing the pressure of water in an autoclave? (choose all that apply) a) increases the boiling point of water b) decreases the boiling point of water c) directly kills microbes d) increases the temperature at which steam forms
increases the boiling point of water increases the temperature at which steam forms
Healthcare-associated infection (HAI)
infections acquired while receiving treatment in a hospital or other healthcare facility
______ provides an alternative to heat for sterilization and disinfection, but the process damages some types of plastics a) autoclaving b) irradiation c) boiling d) dry heat
irradiation
ozone a) breaks down microbial cell walls b) is a strong oxidizing agent c) cross-links proteins
is a strong oxidizing agent
prior to being used to grow cultures, media is ______ to ensure that the cultures remain pure a) heated b) sterilized c) disinfected d) sanitized
sterilized
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.
it immediately kills all bacteria when applied to a wound
although generally less reliable than heat, germicidal chemicals are especially useful for treating... (choose all that apply) a) large surfaces b) microbial media c) food items d) glassware e) heat-sensitive items
large surfaces heat-sensitive items
______, or freeze-drying, is used to preserve coffee, milk, meats, and vegetables.
lyophilization
Identify the difference between the use of depth filters and membrane filters in sterilizing fluids. a) Depth filters have much smaller pores than membrane filters, and are therefore far more efficient than membrane filters. b) Membrane filters have smaller pores than depth filters, but depth filters have complex passages that retain microbes while letting the fluid through. Both methods are efficient. c) These two methods of filtration cannot be compared because they are vastly different in their mechanisms of action in sterilizing fluids. d) Depth filters have very large pores and are an older and much less efficient way of removing microbes from fluids than membrane filters. e) Membrane filters have much smaller pores than depth filters, and are therefore far more efficient than depth filters.
membrane filters have smaller pores than depth filters, but depth filters have complex passages that retain microbes while letting the fluid through. both methods are efficient
Select the method that would be used to sterilize a liquid containing vitamin B12 and human growth hormone a) membrane filtration b) microwaving c) freezing d) HEPA filtration e) boiling f) pasteurization
membrane filtration
depth filters work by which of the following mechanisms? (choose all that apply) a) microbes are trapped in the complex matrix b) microbes are too large to fit through the filter pores c) electrical charges help to retain microbial cells d) microbes are killed as they pass through
microbes are trapped in the complex matrix electrical charges help to retain microbial cells
many germicides lose their effectiveness in the presence of a) bacteria b) organic matter c) light d) pathogens e) acidity
organic matter
when boiling or pasteurizing a sample, microorganisms are destroyed because their a) dna is mutated b) proteins are irreversibly denatured c) rna hybridizes with other single strands of nucleotides
proteins are irreversibly denatured
decontamination
reduces number of pathogens to a safe level
______ is the removal or destruction of all microorganisms and viruses on or in a product
sterilization
Select the reasons sugar or salt can be used for food preservation. (choose all that apply) a) they cause lyophilization b) they disrupt the cytoplasmic membrane c) they may cause plasmolysis d) they create a hypotonic environment, unfavorable for growth e) they create a hypertonic environment, unfavorable for growth f) they dehydrate the bacterial cells
they may cause plasmolysis they create a hypertonic environment, unfavorable for growth they dehydrate the bacterial cells
hot solutions of hydrogen peroxide are often used as a sterilant ______. a) on open wounds b) to produce juice and milk containers c) on our skin, nails, and hair
to produce juice and milk containers
which of the following are physical ways to remove or destroy microbes? (choose all that apply) a) hydrogen peroxide b) ultraviolet radiation c) filtration d) autoclaving e) incineration
ultraviolet radiation filtration autoclaving incineration
germicidal chemicals ______ (choose all that apply) a) usually react irreversibly with proteins, dna, cytoplasmic membranes, or viral envelopes b) have mechanisms of action that are well characterized c) are generally more reliable than heat d) are often poorly understood with regards to mechanisms of action
usually react irreversibly with proteins, dna, cytoplasmic membranes, or viral envelopes are often poorly understood with regards to mechanisms of action
Which of the following destroys acellular infectious agents? a) bacteriocides b) insecticides c) fungicides d) antibiotics e) virucides f) all of the choices are correct
virucides
when would it be a better idea to use a filter vs. an autoclave to sterilize a solution? a) when the solution is heat sensitive b) when the solution is UV sensitive c) when the solution has a high salt content
when the solution is heat sensitive
chlorine-releasing compounds such as sodium hypochlorite are used for all of the following except a) sewage and waste water disinfection b) food equipment sanitation c) wound treatment and skin cleansing d) swimming pool treatments e) household cleaning
wound treatment and skin cleansing
