Chapter 5 Control of MIcrobial Growth Flashcards
(113 cards)
1
Q
Joseph Lister
A
man who saved more lives by the introduction of his system than all the wars of the 19th century. Applied carbolic acid to wounds to prevent gangrene. sterilizing instruments, clean areas.
2
Q
Sterile
A
a sterile item is one that is free of microbes, including endospores and viruses. (does not include prions)
3
Q
Sterilization
A
removal or destruction of all microorganisms and viruses on a product
4
Q
Disinfection
A
the elimination of most or all pathogens on a material. (some living microbes remain)
5
Q
Disinfectants
A
antimicrobial chemicals used for disinfecting inanimate objects. they are toxic to many forms of life, and therefor biocides (bio means life and cida means to kill)
6
Q
Germicides
A
chemicals that target microorganisms and viruses
7
Q
Bactericidal
A
they kill bacteria
8
Q
Antiseptics
A
antimicrobial chemicals non toxic enough to be used on skin or other body tissue. these are routinely used to decrease bacterial numbers on skin before invasive procedures such as surgery.
9
Q
pasteurization
A
a brief heat treatment that reduces the number of spoilage organisms and destroys pathogens. foods and inanimate objects can be pasteurized.
10
Q
decontamination
A
a process used to reduce the number of pathogens to a level considered safe to handle. the treatment can be as simple as thorough washing, or it may involve the use of heat or disinfectants
11
Q
Sanitization
A
generally implies a process that substantially reduces the microbial population to meet accepted health standards. most people also expect a sanitized object to look clean. note that this term does not indicate any specific level of control
12
Q
preservation
A
the prcoess of delaying spoilage of foods or other perishable products. one way to do this is to adjust storage conditions to slow microbial growth. alternatively, chemical preservatives can be added. (bacteriostatic)
13
Q
bacteriostatic
A
chemical preservatives that inhibit growth of bacteria but do not kill them.
14
Q
disinfection by-products (DBP)
A
compounds formed when chlorine or other disinfectants react with naturally occurring chemicals in water
certain pathogens, particularly, Cryptosporidium parvum, a cause of diarrhea, can survive traditional disinfection procedures. to address these problems, water treatment regulations now require facilities to minimize the level of both BDP’s and C. parvum in treatdd water.
15
Q
Bacterial endospores
A
the endospores of Bacillus, Clostridium and related genera are the most resistant form of life typically encountered. only extreme heat or chemical treatment ensures their complete destruction.
16
Q
Protozoan cysts and oocysts
A
cysts and oocysts are stages in the life ciycle of certain intestinal protozoan pathogens such as Giardia lamblia and Cryptosporidium parvum. these disinfectant-resistant forms are excreted in the feces of infected animals, including humans, and can cause diarrheal disease if ingested. Unlike endospores, they are easily destroyed by boiling.
17
Q
Mycobacterium species
A
the waxy cell walls of mycobacteria make them resistant to many chemical treatments. because of this, stronger, more toxic chemicals must be used to disinfect environments that may contain Mycobacterium tuberculosis, the cause of tuberculosis.
18
Q
Pseudomonas species.
A
these commonb environmental organisms are not only resistant to some disinfectants, but in some cases actually grown in them. Pseudomonas species can cause serious healthcare associated infections.
19
Q
Naked viruses
A
Viruses such as poliovirus that lack a lipid envelope are more resistant to disinfectants. conversely, enveloped viruses, such as HIV, tend to be very sensitive to these chemicals.
20
Q
Decimal reduction time or D value
A
the time required for killing 90% of a bacterial population under specific conditions.
the temperature is indicated by a subscript, for example D121.
A one D process reduces the number of cells by one exponent. thus if the D value for an organism is 2 minutes then it would take 4 minutes (2 D values) to reduce a population of 100 (10^2) cells to only one 10^0 survivor.
21
Q
Critical Instruments
A
these come into direct contact with body tissues. they include needles and scalpels. critical instruments must be sterile
22
Q
Semicritical instruments
A
these come into contact with mucous membranes, but do not penetrate body tissure; they include gastrointestinal endoscopes and endotraceal tubes. semicritical instruments must be free of all viruses and begetative bacteria. the few endospores that may remain pose little risk for infection because mucous membranes are effective barriers against their entry into deeper tissue.
23
Q
Non-critical instruments and surfaces
A
these come into contact only with unbroken skin so they pose little risk for infection. countertops, stethoscopes, and blood pressure cuffs are examples of non-critical items.
24
Q
Moist heat
A
most heat destroys mocrobes by irreversibly denaturing their proteins. examples of moist heat treatment include boiling, pasteurization, and pressurized steam.
25
Boiling (moist heat)
Boiling (100 C at sea level) easily destroys most microorganisms and viruses. because of this, drinking water that might be contaminated during floods or other emergency situations should be boiled for at least 5 minutes. boiling is not a method of sterilization, however, because endospores can survive the process.
26
Pasteurization (moist heat)
Louis Pasteur developed the brief heat treatment we now call pasteurization as a way to prevent spoilage of wine. today pasteurization is still used to destroy heat sensitive spoilage organisms in foods and beverages, increasing the products shelf life without significantly altering its quality. (milks juices etc. preventing tuberculosis, brucellosis, salmonellosis, and typhoid fever.
High temperature-short time (HTST). is used with this, milk cooked to 72 C for 15 seconds.
Shelf stable boxed juices and milk are treated using Ultra high temperature (UHT). This destroys all microorganisms that can grown under normal storage conditions, so it is referred to as ultra pasteurization. The UHT process for milk requires rapidly heating the milk to 140 C, holding it at that temp for a few seconds, then cooling quickly.
27
Sterilization using pressurized steam (moist heat)
Heat and moisture tolerant items such as surgical instruments etc are sterlized using autoclaves. Water in a chamber in the autoclave is heated to form steam, causing the pressure in the chmber to increase. the higher pressure in turn increases the temperature at which steam forms. steam at atmospheric pressure never exceeds 100 C but steam at an additional 15 psi is 121 C a temperature that kills even endospores. the pressure itself plays no direct role in the killing.
Typical sterilization us 15 psi 121 C for 15 minutes
28
Commercially sterile
canned foods are commercially sterile meaning that the endospores of some thermophiles may survive. these are usually not a concern, however, because they grow only at temperatures well above those of normal storage.
29
Dry heat
not as efficient as moist heat in killing microbes.
30
incineration
burns cell components to ashes. flaming of wire inoculating loops. also used to destroy medical wastes and contaminated animal carcasses
31
Dry heat ovens
destroys cell components and denatures proteins. less efficient than moist heat, requiring longer times and higher temperatures.
used for laboratory glassware, powders, oils and other dry materials are also sterilized in ovens.
32
Filtration
Recall that membrane filitration, used to determine the number of bacteria in a liquid medium, retains bacteria while allowing the fluid to pass through. that same principle can be used to physically remove microbes from liquids or air.
33
Filtration of fluids
used to remove organisms from heat sensitive fluids such as sugar solutions, beer and wine.
34
Filtration of Air
high efficiency particulate air (HEPA) filters remove nearly all airborne particles that are 0.3 micrometers or larger. these are used for keeping microorganisms out of specialized hospital rooms designed for patients extremely susceptible to infection. the filters are also used in biological safery cabinets in which laboratory personnel work with dangerous airborne pathogens such as Mycobacterium tuberculosis. a continuous stream of incoming and outgoing air flows through HEPA filters to hold microbes within the cabinet. the cabinets are also used to protect samples from contamination.
35
RADIATION
Radio waves, microwaves, visible and ultraviolet light rays, x rays, and gamma rays are all examples of ELECTROMAGNETIC RADIATION. this is a form of energy that travels in waves and has no mass; the amount of energy is related to the wavelength, which is the distance from crest to crest of a wave. the wavelength is inversely proportional to the frequency, the number of waves per second. radiation that has short waves, and therefor high frequency has jore energy thatn that which has long waves and short frequency. the full range of wavelengths is called the electromagnetic spectrum
36
Ionizing radiation
Destroys DNA and possibly damages cytoplasmic membranes. produces reactive molecules that damage other cell components. items can be sterilized even after packaging
used to sterilize heat sensitive materials including medical equipment, disposable surgical supplies, and drugs such as penicillin. also used to destroy microbes in spices, herbs, and approved types of produce and meats.
37
ultraviolet radiation
damages DNA. penetrates poorly
| used to destroy microbes in the air and drinking water, and to disinfect surfaces.
38
High Pressure
high pressure processing is used to decrease the number of microbes in commercial food products such as guacamole, without using high temperatures. the process, which uses pressure of up to 130,000 psi is thought to destroy microbes by denaturing treated products keep the color and flavor associated with fresh foods.
39
Sterilants
these can destroy all microorganisms, including endospores and viruses. they are also called sporocides. destruction of endospores usually requires a 6-10 hour treatment. sterilants are used to treat heat sensitive critical instruments such as scalpels.
40
High-level disinfectants
these destroy all viruses and vegetative microorganisms, but they do not reliably kill endospores. most are simply sterilants used for short time periods, not long enough to ensure endospore destruction. they are used to treat semicritical instruments such as gastrointestinal endoscopes
41
Intermediate level disinfectants
these destroy all vegetative bacteria including mycobacteria, fungi, and most, but not all viruses. they do not kill endospores even with prolonged exposure. this group of germicides is used to disinfect noncritical instruments such as stethoscopes.
42
Low level disinfectants
these destroy fungi, vegetative bacteria except mycobacteria and eveloped viruses. they do not kill endospores, nor do they always destroy naked viruses. intermediate level and low level disinfectants are also called general purpose disinfectants. in hospitals, they are used for disinfecting furniture floors and walls.
43
Alcohols
easy to obtain and inexpensive, rapid evaporation limits their contact time.
USED for aqueous solutions of alcohol as used as antiseptics to clean skin in preparation for procedures that break intact skin, and as disinfectants for treating instruments.
44
Aldehydes (glutaraldehyde, orthophthalaldehyde, and formaldehyde)
capable of destroying all microbes. irritating to the respiratory tract, skin and eyes
Glutaraldehyde and orthophthalaldehyde are used to sterilize medical instruments. formalin is used in vaccine production and to preserve biological specimens.
45
Biguanides (chlorhexidine)
the most effective of a group of chemicals called biguanides is extensively used in antiseptic products. it stays on skin and mucous membranes, is of relatively low toxicity, and destroys a wide range of microbes, including vegetative bacteria, fungi and some enveloped viruses. Chlorhexidine is an ingredient is many products including antiseptic skin creams, dininfectants, and mouthwashes. Chlorhexidine-imnpregnated catheters and implanted surgical mesh are used in medical procedures. even tiny chips that slowly release chlorohexidine have been developed; these are inserted into periodontal pockets to treat gum disease. adverse side effets of chlorhexidine are rare, but severe allergic reactions have been reported.
46
Ethylene Oxide Gas
easily penetrates hard to reach places and fabrics and dose not damage moisture sensitive material. it is toxic, explosive, and may be carcinogenic.
commonly used to sterilize medical devices.
47
Halogens (chlorine and iodine)
Chlorine solutions are inexpensive and readily available; however, organic compounds and other impurities neutralize the activity. some forms of chlorine may react with oranic ompounds to form toxic chlorinated products. iodine is more expensive than chlorine and does not reliably kill endospores.
Solutions of chlorine are widely used to disinfect inanimate objects, sufrfaces, drinking water, and wasterwater. tincture of iodine and iodophores can be used as disinfectants or antiseptics
48
Metal Compounds
Metal compounds kill mirroorganisms by combining with sulfhydryl groups (-SH) of enzymes and other proteins, thereby interfering with their function. high concentrations of most metals are too toxic to human tissue to be used medically.
Silver is one of the few metals still used as a disinfectant. Creams containing silver sulfadiazine, a combination of silver and a sulfa drug, are applied topically to prevent infection of second and third degree burns.
49
Ozone
Ozone (03) an unstable form of oxygen is a powerful oxidizing agent. it decomposes quickly, however, so it must be generated on site, usually by passing air or O2 between 2 electrodes. ozone is used as an alternative to chlorine for disinfecting drinking water and wastewater.
50
Peroxgens (hydrogen peroxide and peracetic acid)
readily biodegradable and less toxic than traditional alternatives. the effectiveness of hydrogen peroxide as an antiseptic is limited because the enzyme catalase breaks it down. peracetic acid is a more potent germicide than hydrogen peroxide.
Hydrogen peroxide is used to sterilize containers for asceptically packaged juices and milk. peracetic acid is widely used to disinfect and sterilize medical devices.
51
Phenolic Compounds (triclosan and hexachlorophene)
wide range of activity, reasonable cost, remains effective in the presence of detergents and organic contaminants, leaves on active antimicrobial residue
Triclosan is used in a variety of personal care products, including toothpastes, lotions, and deodorant soaps. hexachlorophene is highly effective against Staphylococcus aureus, but its use is limited because it can cause neurological damage.
52
Quaternary Ammonium Compounds (benzalkonium chloride and cerylpyridinium chloride)
Non toxic enough to be used on food preparation surfaces. inactivated by anionic soaps and detergents.
Widely used to disinfect inanimate objects and to preserve non food substances.
53
Lister developed his ideas on prevention of infection during medical procedures after studying the work of
A. Koch.
B. Pasteur.
C. Jenner.
D. Fleming.
B. Pasteur.
54
One of the first chemicals used by Lister to prevent surgical infections was
A. alcohol.
B. iodine.
C. carbolic acid.
D. mercury.
C. carbolic acid.
55
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.
A. sterilization.
56
A sterile item is free of
A. microbes.
B. endospores.
C. viruses.
D. prions.
E. microbes, endospores AND viruses.
E. microbes, endospores AND viruses.
57
A suffix used to describe a killing action would be
A. -static.
B. -cidal.
C. -cillin.
D. -tion.
B. -cidal.
| playing "recitals" KILLED ME! they were the worst
58
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.
B. is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.
59
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.
B. very effective at the mechanical removal of microorganisms.
60
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.
E. are acquired while in the hospital AND occur because of a susceptible population and presence of disease causing organisms.
61
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.
E. All of the choices are correct.
62
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.
E. All of the choices are
63
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.
C. Pseudomonas aeruginosa.
64
12. 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.
B. die at a constant proportion.
65
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
D. 10
66
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
D. 6 minutes
67
Microbial death rates may be affected by
A. pH.
B. temperature.
C. the presence of organics.
D. All of the choices are correct.
D. All of the choices are correct.
68
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
B. washing/mechanical removal of bacteria/organic matter
69
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.
A. irreversible coagulation of proteins.
70
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.
B. heat resistant endospores are unaffected.
71
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.
B. 121°C at 15 psi for 15 minutes.
72
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
A. dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes
73
Which of the following is not a sterilization method?
A. hot air oven
B. autoclave
C. pasteurization
D. filtration
C. pasteurization
74
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
C. Ultrahigh-temperature (UHT) method
75
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.
E. heat sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus.
76
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.
E. are geared to destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D (designed to kill 1012 endospores) processes.
77
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.
C. in a hot air oven.
78
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.
D. sterilize the inoculating loop.
79
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.
C. lyophilization.
80
Generally, membrane filters are not used to remove
A. bacteria from liquids.
B. microorganisms from gases.
C. spoilage agents from alcoholic beverages.
D. enzymes.
D. enzymes.
81
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.
A. producing reactive molecules such as superoxide and hydroxyl free radicals.
82
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.
B. can be used to either sterilize or pasteurize, depending on the dose of radiation.
83
Which would be most effective against Pseudomonas?
A. alcohol
B. radiation
C. quaternary ammonium compounds
D. iodophors
B. radiation
84
Ultraviolet radiation at the bactericidal wavelength destroy bacteria by
A. destroying endospores.
B. damaging nucleic acid.
C. preventing spore formation.
D. denaturing proteins.
B. damaging nucleic acid.
85
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.
A. the heat they generate in a product.
86
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.
E. All of the choices are true.
87
Alcohols are not reliably effective at destroying
A. vegetative bacteria.
B. enveloped viruses.
C. naked viruses.
D. endospores.
E. naked viruses AND endospores.
E. naked viruses AND endospores.
88
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.
E. is, if given enough time, able to destroy all forms of microbial life AND is very good for use on heat-sensitive
89
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.
E. is a member of the biguanides AND is extensively used in antiseptics.
90
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.
E. is very useful for sterilizing heat or moisture sensitive items AND is potentially carcinogenic.
91
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.
E. readily reacts with organics to produce potentially carcinogenic trihalomethanes AND is an effective, inexpensive, disinfectant able to destroy all types of microorganisms.
92
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.
E. All of the choices are true
93
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.
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.
94
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.
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.
95
Hexachlorophene has been particularly effective against
A. Staphylococcus aureus.
B. Micrococcus aureus.
C. Escherichia coli.
D. Enterobacter aerogenes.
A. Staphylococcus aureus.
96
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.
E. cationic detergents which help wash surfaces AND attracted to the negative charge on the microbial cell surface.
97
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.
B. inhibit the germination of Clostridium botulinum endospores.
98
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.
E. All of the choices are correct.
99
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.
C. prevent infection of second- and third-degree burns.
100
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.
D. their use contributes to serious pollution of natural waters.
101
Prions and viroids are easily destroyed by common sterilization procedures.
FALSE
102
The endospores of Pseudomonas make that organism very difficult to kill.
FALSE
103
Upon heat treatment, bacteria die at a constant proportion.
TRUE
104
The more bacteria one starts with, the longer it will take to kill them all.
TRUE
105
Heat treatment is an effective method for sterilization or disinfection of all materials
FALSE
106
Boiling is very effective at removing most common waterborne pathogens.
TRUE
107
Pasteurization results in the sterilization of food products.
FALSE
108
Dry heat takes a much shorter time to sterilize material than wet heat.
FALSE
109
100% ethanol is twice as effective as 60% ethanol at controlling bacteria.
FALSE
110
Generally, heavy metals, except silver, have been proven to be too toxic for use on human tissue and are no longer used medically.
TRUE
111
Hydrogen peroxide may be used as a sterilant on living tissue.
FALSE
112
Cold and freezing are very effective in killing bacteria.
FALSE
113
Organic acids, such as benzoic acid, are often added to foods to prevent microbial growth
TRUE
