Chapter 9

Question 1

Sterilization does not apply to prions which are infectious proteins because?

Answer 1

Standard sterilization techniques do not destroy them

Question 2

In practical terms, sterilization indicates only the?

Answer 2

Eradication (complete destruction of something) of harmful microorganisms and viruses ; some innocuous microbes may still be present & viable in an environment that is considered sterile

Question 3

Does commercial sterilization of canned foods kill all hyperthermophilic microbs?

Answer 3

No, however, because they do not cause disease & they cannot grow & spoil food at ambient temperatures, they are of no practical concern

Question 4

An environment or procedure free of contamination by pathogens

Answer 4

Aseptic

Question 5

Vegetables & fruit juices are available in _______ packaging, & surgeons & lab technicians use _______ techniques to avoid contaminating a surgical field or lab equipment

Answer 5

Aseptic

Question 6

Refers to the use of physical or chemical agents known as _______, including ultraviolet light, heat, alcohol, and bleach, to inhibit or destroy microorganisms, especially pathogens

Answer 6

Disinfection

disinfectants

Question 7

Unlike sterilization, disinfections does not guarantee that?

Answer 7

All pathogens are eliminated, indeed disinfectants alone cannot inhibit endospores or some viruses

Question 8

The term disinfection is only used when?

Answer 8

In reference to treatment of inanimate objects, when a chemical is used on skin or other tissue, the process is called antisepsis

Question 9

The term disinfection is only used when?

Answer 9

In reference to treatment of inanimate objects, when a chemical is used on skin or other tissue, the process is called antisepsis, and the chemical is called an antiseptic

Question 10

Though chemicals such as soap or alcohol are common during degerming, the action of?

Answer 10

Thoroughly scrubbing the surface may be more important than the chemical in removing microbes

Question 11

Steam, high-pressure hot water, & scrubbing are used to?

Answer 11

Sanitize restaurant utensils and dishes, & the chemicals are used to sanitize public toilets

Question 12

The difference between disinfecting dishes at home and sanitizing dishes in a restaurant is the?

Answer 12

Arena, private verses public in which the activity takes place

Question 13

There are two major types of microbial control

Answer 13

Sterilization, which is the elimination of all microbes; and antisepsis or disinfection, which each denote the destruction of vegetative (non spore) cells & many viruses

Question 14

Chemical agents that destroy pathogenic microorganisms in general

Answer 14

Germicides

Question 15

Define microbial death

Answer 15

The permanent loss of reproductive ability under ideal environmental conditions

Question 16

One technique for evaluating the efficacy of an antimicrobial agent is to calculate the microbial death rate which is?

Answer 16

Usually found to be constant over time for any particular microorganism under a particular set of conditions

Question 17

Describe how to evaluate the efficacy of an antimicrobial agent by calculating the microbial death rate

Answer 17

A scientist treats a broth containing 1 billion (10 to the 9th) microbes with an agent that kills 90% of them in 1 minute. The most susceptible cells die first, leaving 100 million (10 to the 8th) hardier cells after the first minute. After another minute of treatment, another 90% die leaving 10 million (10 to the 7th) cells that have even greater resistance to and require longer exposure to the agent before they die.

Question 18

There are many types of chemical & physical microbial controls, but their modes of action fall into two basic categories

Answer 18

1) Those that disrupt the integrity of cells by adversely altering their cell walls or cytoplasmic membranes
2) Those that interrupt cellular metabolism & reproduction by interfering with the structures of proteins & nucleic acids

Question 19

Describe how alteration of cell walls and membranes is a mode for microbial control

Answer 19

Beneath a cell wall is a cytoplasmic membrane which acts as a bag that contains the cytoplasm & it controls the passage of chemicals into and out of the cell. Extensive damage to a membranes proteins or its phospholipids by any physical or chemical agent allows the cellular contents to leash out and if it’s not immediately repaired it will cause death

Question 20

Describe the alteration of cell walls and membranes is a mode for microbial control for enveloped viruses

Answer 20

The envelope is a membrane composed of proteins & phospholipids that is responsible for the attachment of the virus to its target cell; thus when damage happens to the envelope by physical or chemical agents it fatally interrupts viral replication. The lack of an envelope in non enveloped viruses accounts for their greater tolerance of harsh environmental conditions, including antimicrobial agents

Question 21

Describe the damage to proteins and nucleic acids which is a mode that antimicrobal agents use

Answer 21

A proteins function depends on an exact three-dimensional shape, which is maintained by hydrogen & disulfide bonds between amino acids. When these bonds are broken by extreme heat or certain chemicals, the proteins shape changes. These denatured proteins cease to function, bringing cellular death. Chemicals, radiation & heat can alter and even destroy nucleic acids. Since genes of a cell/virus are composed of nucleic acids disruption of these molecules can produce fatal mutations

Question 22

Describe how antimicrobial agents can interfere with protein synthesis

Answer 22

The portion of a ribozyme that catalyzes the synthesis of proteins is a ribozyme (an enzymatic enzyme) so physical or chemical agents that interfere with nucleic acids also stop protein synthesis

Question 23

Temp. & pH affect microbial death rates & the efficacy of antimicrobial methods. Warm disinfectants generally work better than cool ones because?

Answer 23

Chemicals react faster at higher temps.

Question 24

Acidic conditions enhance the antimicrobial effect of heat. Some chemical disinfectants, such as household chlorine bleach are more effective at?

Answer 24

Low pH

Question 25

Why is it important to clean objects before sterilization or disinfection?

Answer 25

Organic materials like fat, feces, vomit, blood and the intercellular secretions in biofilms interferes w/the penetration of heat, chemicals & some forms of radiation . In some cases these materials inactivate chemical disinfectants.

Question 26

Why is it important to clean objects before sterilization or disinfection so that antimicrobial agents can thoroughly contact all the objects surfaces?

Answer 26

Organic materials like fat, feces, vomit, blood and the intercellular secretions in biofilms interferes w/the penetration of heat, chemicals & some forms of radiation . In some cases these materials inactivate chemical disinfectants.

Question 27

A phenol coefficient greater than 1.0 indicates that?

Answer 27

An agent is more effective than phenol, and the larger the ratio the greater the effectiveness

Question 28

Heat can be used for sterilization (all cells & viruses are deactivated) or for commercial preparation of canned goods. In commercial sterilization what happens?

Answer 28

Hyperthermophilic prokaryotes remain viable but are harmless because they can't grow at the normal (room) temp. in which canned foods are stored

Question 29

lowest temp. that kills all cells in a broth in 10 minutes

Answer 29

Thermal death point

Question 30

The time it takes to completely sterilize a particular volume of liquid at a set temperature

Answer 30

Thermal death time

Question 31

Time required to destroy 90% of the microbes in a sample

Answer 31

Decimal reduction time (D). Researchers calculate this when measuring the effectiveness of heat sterilization. This concept is useful to food processors because they must heat foods to eliminate all endospores of Clos. botulinum which could germinate & produce botulism toxin inside sealed cans

Question 32

The standard in food processing is to apply heat such that a population of 10 to the 12th pwr C. botulinum endospores is reduced to?

Answer 32

10 to the 0 pwr (that is 1) endospore which leaves only a small change that the can of food contains an endospore

Question 33

Moist heat is commonly used to?

Answer 33

Disinfect, sanitize, sterilize, and pasteurize, kills cells by denaturing proteins & destroying cytoplasmic membranes

Question 34

Moist heat is more effective in microbial control than dry heat because?

Answer 34

Water is a better conductor of heat than air. Example, you can safely stick into an oven at 350 degrees F for a few moments but putting it into boiling water at the lower temperature of 212 degrees F would severely burn you

Question 35

Boiling kills the?

Answer 35

Vegetative cells of bacteria & fungi, the trophozoites of protozoa, & most viruses within 10 minutes at sea level

Question 36

Water at a rapid boil is no hotter than that at a slow boil; boiling water at normal atmospheric pressure cannot exceed boiling temperature (100 degrees C at sea level) why is that?

Answer 36

Because escaping steam carries excess heat away

Question 37

For boiling the time is the critical factor. Also at higher elevations water will boil at?

Answer 37

Lower temps. because atmospheric pressure is lower, thus, a longer boiling time is required in Denver than in LA to get the same antimicrobial effect

Question 38

What can survive boiling at sea level?

Answer 38

Bacterial endospores, protozoan cysts, and some viruses (hepatitis) can survive boiling at sea level for many minutes or even hours. Because they can withstand boiling for more than 20 hrs, boiling is NOT recommended when true sterilization is required.

Question 39

Boiling is effective for?

Answer 39

Sanitizing restaurant tableware or disinfecting baby bottles

Question 40

True sterilization using heat requires what?

Answer 40

Higher temps. than that of boiling water. To achieve higher temperatures, pressure is applied to boiling water in order to prevent the escape of heat in steam.

Question 41

Why does applying pressure achieve sterilization?

Answer 41

The temperature at which water boils (& steam is formed) increases as pressure increases

Question 42

Who uses autoclaving techniques?

Answer 42

Scientists and medical personnel routinely use a piece of equipment called an autoclave to sterilize chemicals & objects that can tolerate moist heat. There are alternative techniques that must be used for the items that are damaged by heat or water, such as some plastics & vitamins

Question 43

An autoclave (used by scientists & medical personnel) consists of what?

Answer 43

A pressure chamber, pipes to introduce

Question 44

An autoclave (used by scientists & medical personnel) consists of what?

Answer 44

A pressure chamber, pipes to introduce & evacuate steam, valves to remove air & control pressure, & pressure & temp. gauges to monitor the procedure. As steam enters an autoclave chamber, it forces air out, raises the temp. of the contents, & increases the pressure, until a set temp. & pressure are reached

Question 45

What is the temp. and pressure to destroy all microbes and how long does it take.

Answer 45

Temp. of 121 Degrees C, which requires the addition of 15 pounds per square inch (psi) of pressure above that of normal air pressure this destroys all microbes in a small volume in about 10 minutes, it can hold pressure & temp. for 15 minutes for a safety margin

Question 46

Can an autoclave sterilize large volumes of liquids & solids?

Answer 46

Yes it is just a slower process because they require more time for heat to penetrate. Thus, it requires more time to sterilize 1 liter of fluid in a flask than the same volume of fluid distributed into smaller tubes. Autoclaving solid substances such as meat also requires extra time because it takes longer for heat to penetrate to their centers

Question 47

Sterilization in an autoclave requires?

Answer 47

That steam be able to contact all liquids & surfaces that might be contaminated with microbes; therefore, solid objects must be wrapped in porous cloth or paper, not sealed in plastic or aluminum foil, which are impermeable to steam. Containers of liquids must be sealed loosely enough to allow steam to circulate freely, and all air must be forced out by steam. Since steam is lighter than air, it cannot force air form the bottom of an empty vessel; empty containers must be tipped so that air can flow out

Question 48

What are ways to ensure that an autoclave has sterilized its contents?

Answer 48

A common method is a chemical that changes color when the proper combination of temp. & time have been reached. Often this color indicator is impressed in a pattern on tape or paper so the word sterile or a pattern or design appears. Another method use plastic beads that melt when proper conditions met

Question 49

A biological indicator of sterility used endospores of the bacterium Bacillus stearothermophilus impregnated into tape. After autoclaving, the tape is?

Answer 49

Aseptically inoculated into sterile broth. If no bacterial growth appears, the original material is considered sterile. In a variant of this technique the endospores are on a strip in one compartment of a vial that also induces a growth medium containing a pH color indicator. After autoclaving, a barrier between the two compartments is broken, putting the endospores into contact with the medium. In this case the absence of a color change after incubation indicates sterility

Question 50

What types of bacteria are controlled by pasteurization?

Answer 50

Brucella melitensis, Mycobacterium bovis, and Escherichia coli, the causative agents of undulant fever, bovine tu

Question 51

What types of bacteria are controlled by pasteurization?

Answer 51

Brucella melitensis, Mycobacterium bovis, and Escherichia coli, the causative agents of undulant fever, bovine tuberculosis, and one kind of diarrhea, are controlled in this manner

Question 52

Moist Heat Treatments of milk: Process | 1) Historical (batch) pasteurization

Answer 52

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Question 53

Moist Heat Treatments of milk: Process 1) Historical (batch) pasteurization

Answer 53

Treatment

Question 54

``` Moist Heat Treatments of milk: Process 1) Historical (batch) pasteurization 2) Flash pasteurization 3) Ultrahigh-temperature pasteurization 4) Ultrahigh-temperature sterilization ```

Answer 54

Treatment 1) 63 Degrees C for 30 minutes 2) 72 Degrees C for 15 seconds 3) 135 Degrees C for 1 second 4) 140 Degrees C for 1-3 seconds

Question 55

Pasteurization is not sterilization. Thermoduric and theromphilic- heat tolerant and heat loving- prokaryotes survive pasteurization, but they do not?

Answer 55

Cause spoilage over the relatively short times during which properly refrigerated and pasteurized foods are stored before consumption.

Question 56

The combination of time and temperature required for effective pasteurization varies with the product. Milk is the most familiar pasteurized product. Describe the pasteurization of milk

Answer 56

Historically milk was pasteurized by batch method for 30 minutes at 63 Degrees C, but most milk processors today use a high temperature short time method known as flash pasteurization, in which milk flows through heated tubes that raise its temperature for 72 degrees C for only 15 seconds. This treatment effectively destroys all pathogens. Ultrahigh-temperature pasteurization heats the milk to 134 Degrees C for only 1 second, some consumers claim it adversely affects the taste

Question 57

What is ultrahigh-temperature sterilization?

Answer 57

The dairy industry and other food processors use it which involves flash heating milk or other liquids to rid them of all living microbes. Process involves passing liquid through superheated steam at 140C for 1-3 seconds and then cooling rapidly. Treated liquids can be stored indefinitely at room temp. w/out microbial spoilage, though after months of storage chemical degradation results in flavor changes. Small packages of dairy creamer served in restaurants are often sterilized by this method

Question 58

For substances such as powders & oils that cannot be sterilized by boiling or with steam, or for materials that can be damaged by repeated exposure to steam (such as some metal objects, sterilization can be achieved by?

Answer 58

The use of dry heat, as occurs in an oven

Question 59

Why is hot air an effective sterilization agent?

Answer 59

Because it denatures proteins and fosters the oxidation of metabolic & structural chemicals; however in order to sterilize, dry heat requires higher temps. for longer times than moist heat because dry heat penetrates more slowly. For instance, whereas an autoclave needs less than 15 minutes to sterilize an object at 121C, an oven at the same temp. requires at least 16 hours to achieve sterility. Typically use higher temps (171C for 1 hr or 160C for 2 hrs) to sterilize objects in an oven, but objects made of rubber, paper & many types of plastic oxidize rapidly (combust) under these conditions

Question 60

Complete incineration is the ultimate means of sterilization.

Answer 60

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Question 61

Complete incineration is the ultimate means of sterilization. As part of standard aseptic technique in microbiological laboratories, inoculating loops are sterilized by heating them in the flame of a Bunsen burner or with an electric heating coil until?

Answer 61

They glow red (about 1500C). Health care workers incinerate contaminated dressings, bags, and paper cups; field epidemiologists incinerate the carcasses of animals that have diseases such as anthrax or bovine spongiform encephalopathy (mad cow disease)

Question 62

Refrigeration and freezing temperatures

Answer 62

Refrigeration temps.- Between 0 degrees C and 7 C | Freezing temps.- Below 0 degrees C

Question 63

How does refrigeration and freezing control microbial growth?

Answer 63

They decrease microbial metabolism, growth, and reproduction because chemical reactions occur more slowly at low temperatures, and because liquid water is not available at subzero temps. However, psychrophilic (cold-loving) microbes can multi. in refrigerated food and spoil its taste and suitability for consumption

Question 64

Refrigeration halts the growth of most pathogens, which are predominantly mesophiles. Exceptions are?

Answer 64

The bacteria Listeria, which can reproduce to dangerous levels in refrigerated food, and Yersinia which can multiply in refrigerated blood products and be passed onto blood recipients

Question 65

Slow freezing, during which ice crystals have time to form an puncture cell membranes, is more effective than quick freezing in?

Answer 65

Inhibiting microbial metabolism, though microorganisms also vary in their susceptibility to freezing. Whereas the cysts of tape worms perish after several days in frozen meat, many vegetative bacterial cells, bacterial endospores, & viruses can survive subfreezing temperatures for years.

Question 66

Scientists store many bacteria & viruses in low temperature freezers at -30 C to -80 C and are able to reconstitute the microbes into viable populations by warming them in media containing proper nutrients. Therefore because of this we must?

Answer 66

Take care in thawing and cooking frozen food, because it can still contain many pathogenic microbes

Question 67

Desiccation, or drying, has been used for thousands of years to preserve such foods as fruits, peas, beans, grains, nuts, and yeast. Desiccation inhibits what?

Answer 67

Microbial growth because metabolism requires liquid water. Drying inhibits the spread of most pathogens, including the bacteria that cause syphilis, gonorrhea, & the more common forms of bacterial pneumonia & diarrhea. However, most molds can grow on dried raisins, & apricots, which have as little as 16% water content

Question 68

Scientists use lyophilization, a technique combining freezing & drying, to preserve microbes & other cells for many years. In this process?

Answer 68

Scientists instantly freeze a culture in liquid nitrogen or frozen carbon dioxide (dry ice); they they subject it to a vacuums that removes frozen waters through a process called sublimation, in which the water is transformed directly from solid to gas. Lyophilization prevents the formation of large, damaging ice crystals. Although not all cells survive, enough are viable to enable the culture to be reconstitute many years later

Question 69

What is filtration

Answer 69

The passage of a fluid (either liquid or a gas) through a sleeve designed to trap particles- in this case to cells or viruses and separate them from the fluid. Researchers often use a vacuum to assist the movement of fluid through the filter

Question 70

How does filtration work

Answer 70

It traps microbes larger than the pore size, allowing smaller microbes to pass through.

Question 71

In the late 1800s, filters were able to trap cells, but their pores were too large to trap?

Answer 71

The pathogens of such diseases as rabies and measles. These pathogens were thus named filterable viruses, which today have been shortened to viruses. Now filters with pores small enough to trap even viruses

Question 72

In the late 1800s, filters were able to trap cells, but their pores were too large to trap?

Answer 72

The pathogens of such diseases as rabies and measles. These pathogens were thus named filterable viruses, which today have been shortened to viruses. Now filters with pores small enough to trap even viruses are available, so filtration can be sued to sterilize such heat sensitive

Question 73

In the late 1800s, filters were able to trap cells, but their pores were too large to trap?

Answer 73

The pathogens of such diseases as rabies and measles. These pathogens were thus named filterable viruses, which today have been shortened to viruses. Now filters with pores small enough to trap even viruses are available, so filtration can be sued to sterilize such heat sensitive materials as ophthalmic solutions, antibiotics, vaccines, liquid vitamins, enzymes, and culture media

Question 74

In order to construct filters today scientists typically use?

Answer 74

Thin circular membrane filters manufactured of nitrocellulose or plastic and containing specific pore sizes ranging from 25 micrometers to less than 0.01 micrometers in diameter

Question 75

Health care & laboratory workers routinely use filtration to prevent?

Answer 75

Airborne contamination by microbes. Medical personnel wear surgical masks to prevent exhaled microbes from culture vessels to prevent contamination by airborne microbes

Question 76

Another ancient method of microbial control is the used of high concentrations of salt or sugar in foods to inhibit microbial growth by?

Answer 76

Osmotic pressure

Question 77

Osmosis is the net movement of water across a semipermeable membrane (such as the cytoplasmic membrane) from an area of higher concentration to an area of lower concentration.

Answer 77

Cellular metabolism because enzymes are fully functional only in aqueous environments.

Question 78

What does osmosis preserve?

Answer 78

osmosis preserves honey, jerky, jams, jellies, salted fish, and some types of pickles from most microbial attacks

Question 79

Osmosis is the net movement of water across a semipermeable membrane (such as the cytoplasmic membrane) from an area of higher concentration to an area of lower concentration. Cells in hypertonic solution of salt & sugar lose water, and desiccates.

Answer 79

Cellular metabolism because enzymes are fully functional only in aqueous environments.

Question 80

Osmosis is the net movement of water across a semipermeable membrane (such as the cytoplasmic membrane) from an area of higher concentration to an area of lower concentration. Cells in hypertonic solution of salt & sugar lose water, and desiccates.

Answer 80

Removal of water inhibits cellular metabolism because enzymes are fully functional only in aqueous environments.

Question 81

What does osmosis preserve?

Answer 81

Preserves honey, jerky, jams, jellies, salted fish, and some types of pickles from most microbial attacks

Question 82

Fungi have a greater ability than bacteria to tolerate hypertonic environments with little moisture, which explains why?

Answer 82

Jelly in your refrigerator may grow a colony of penicillium mold but is not likely to grow the bacterium Salmonella

Question 83

Another physical method of microbial control is the use of radiation. There are two types of radiation

Answer 83

1) Particulate radiation | 2) Electromagnetic radiation

Question 84

What does particulate radiation consist of?

Answer 84

High-speed subatomic particles, such as protons, that have been freed from their atoms

Question 85

What is electromagnetic radiation?

Answer 85

Energy w/out mass traveling in waves at the speed of light. Energy is released from atoms that have undergone internal changes. The wavelength of electromagnetic radiation, defined as the distance between two crests of a wave, ranges from very short gamma rays, through X rays, ultraviolet light, & visible light, to long infrared rays, & finally to very long radio waves

Question 86

Electromagnetic radiation: Though they are particles, electrons also have a wave nature, with wavelengths that are even shorter than gamma rays.

Answer 86

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