chapter 5 microbiology
Boiling, which involves heating water to______________ oC at sea level, is a method that easily destroys the majority of microorganisms
100
The common parameters used in autoclaving are ______.
121 C at 15 psi for 15 minutes
Aqueous solutions of alcohol at a concentration of ______ are more effective than 100% alcohol.
60-80%
Which of the following are advantages of using ionizing radiation for sterilization?
Can be used on heat-sensitive material Can be used after packaging Effectiveness at killing pathogens
The temperature and time used in the commercial canning process is enough to reduce a population of 1012 _______ endospores to only one spore.
Clostridium botulinum
Which cellular component is damaged by UV radiation?
DNA
Which of the following are goals of pasteurization?
Destroy pathogens Reduce the number of microbes
Depth filters work by which of the following mechanisms?
Electrical charges help to retain microbial cells. Microbes are trapped in the complex matrix.
____________________ oxide is an extremely useful gaseous sterilizing agent that destroys all microbes and is often used to sterilize fabric, equipment, and implantable devices.
Ethylene
True or false: Choosing which germicide to use is not that complicated since we only consider how effective it is against the target microbes.
False
True or false: Ionizing radiation is not an effective method of controlling microbes in food products.
False
_______ does not actually destroy microbes or inhibit their growth but instead removes them physically from samples.
Filtration
_______________is a physical means used for destroying or removing microorganisms.
Filtration
Which of the following are physical ways to remove or destroy microbes?
Filtration Autoclaving Incineration Ultraviolet radiation
_______ is used to kill bacteria and inactivate viruses in vaccines. It can also preserve biological specimens.
Formaldehyde
______ is the destruction of microbes by subjecting them to extremes of dry heat, reducing them to ashes.
Incineration
What are the effects of increasing the pressure of water in an autoclave?
Increases the boiling point of water Increases the temperature at which steam forms
_______ can kill all vegetative bacteria (including mycobacteria), as well as fungi and most viruses. This group of germicides is used to disinfect non-critical instruments such as stethoscopes.
Intermediate-level disinfectants
ultra-high-temperature (UHT) method
Involves a higher temperature for a short time; products can be stored at room temperature
What are characteristics of chlorine when used to disinfect drinking water?
It is effective even at very low levels. It kills many pathogens.
Which of the following are disadvantages of using chlorine to disinfect drinking water?
It reacts with some organic compounds to form potential carcinogens. At the levels used, it does not kill Cryptosporidium parvum oocysts and Giardia lamblia cysts. Organic material disrupts its germicidal activity.
Why is it important to completely remove all traces of ethylene oxide from items used to grow bacteria?
Its persistent effect will not allow the microbes to grow.
Which of the following are effects of ionizing radiation on food products?
Killing of bacterial pathogens Changes in flavor of some foods
What is the major disadvantage of using dry heat instead moist heat to kill microbes?
Longer time requirement
high-temperature-short-time (HTST) method
Most commonly used; products still require refrigeration or freezing
What are the main limitations of using UV radiation?
Safety of use Poor penetration
_____ destroy all microbes, including viruses and endospores.
Sterilants
Which of the following are factors that most affect how much time is needed to kill all organisms in the canning process?
Temperature Concentration of organisms
Which of the following is an advantage of using alcohol solutions for disinfection?
They do not leave a residue.
True or false: Although endospores of certain thermophiles can survive the commercial canning process, these are rarely a concern.
True
_______________light is a form of electromagnetic radiation. In wavelengths from 220-300 nm, it kills microbes via DNA damage.
Ultraviolet
When would it be a better idea to use a filter rather than an autoclave to sterilize a solution?
When the solution is heat sensitive.
To ensure that an autoclave is properly sterilizing, it is important to use ______.
a biological indicator
A tincture is a(n) _______-based solution of an antimicrobial chemical, and it can be more effective than the corresponding aqueous solution.
alcohol
Which of the following chemical classes destroy microorganisms by forming chemical bonds that cross-link and inactivate proteins and nucleic acids?
aldehydes
In addition to destroying C. botulinum endospores, commercial canning also destroys ______.
all other organisms that grow under normal storage conditions
Aldehydes typically kill microbes by ______.
altering nucleic acids altering proteins
Chlorhexidine solutions are commonly used for ______.
antisepsis of skin and skin wound care mouthwashes
It is often difficult to choose which germicide to use because often the most effective options ______.
are not the safest
Aqueous solutions of ethyl or isopropyl alcohol are commonly used as antiseptics and disinfectants because they ______.
are relatively non-toxic do not leave a residue quickly kill vegetative bacteria and fungi are relatively inexpensive
A(n) ________ is an instrument used to carry out sterilization at high temperature and pressure.
autoclave
Chlorhexidine is ______.
bactericidal
Pasteurization is widely used to destroy pathogens in milk and juices. As a result consumers are protected from which of the following diseases?
brucellosis salmonellosis typhoid fever
Silver is used as an antimicrobial in which of the following products? antibiotic ointments burn creams orthopedic braces bandage pads
burn creams bandage pads
How do aqueous solutions of alcohol usually affect microbes?
by denaturing proteins by damaging lipid membranes
Peroxygens are powerful oxidizing agents that ______. are more toxic than the traditional alternatives ethylene oxide and glutaraldehyde can be used as sterilants under controlled conditions do not biodegrade and therefore build up in the environment include hydrogen peroxide and peracetic acid
can be used as sterilants under controlled conditions include hydrogen peroxide and peracetic acid
High pressure (130,000 psi) is thought to kill microbes by altering their ______.
cell membranes proteins
A strong oxidizing agent increasingly being used as a disinfectant and sterilant for treating drinking water, wastewater, and swimming pools is ______.
chlorine dioxide
When filtering fluids, the type of filter called a(n) __________filter trap material within thick, porous filtration material such as cellulose fibers.
depth
UV radiation is used extensively to destroy microbes in ______.
drinking water the air
To achieve equivalent microbial killing, ______ heat requires longer exposure times and higher temperatures than ______ heat.
dry; moist
Radio waves, X-rays, microwaves, UV light and gamma rays are all examples of ______.
electromagnetic radiation
A retort is an industrial-sized autoclave that ensures that ______ are destroyed.
endospores of Clostridium botulinum
True or false: Microwaves always cook foods and kill microbes effectively.
false
The straining of a fluid or air through a membrane to trap microorganisms is known as________.
filtration
A common dry heat sterilization method used in the microbiology laboratory is ______.
flaming the inoculating loop
Formalin is 37% aqueous solution of_______________ that is used as a potent chemical fixative and microbicide.
formaldehyde
Which of the following are examples of ionizing radiation?
gamma rays X-rays
A 2% solution of ______ is used as a liquid chemical sterilant for treating heat-sensitive medical items.
glutaraldehyde
Chlorine and iodine are common disinfectants that belong to a class of chemicals called_______________ .
halogens
Although generally less reliable than heat, germicidal chemicals are especially useful for treating ______.
heat-sensitive items large surfaces
Disinfectants that destroy all viruses and vegetative organisms but not endospores are referred to as_____________ -level disinfectants.
high
Filters designed to remove nearly all airborne particles measuring at least 3 μm are called _____________-______________ _____________ air (HEPA) filters.
high; efficiency; particulate
High-efficiency particulate air (HEPA) filtration may be used in a number of settings, including ______.
hospital rooms passenger aircraft vacuum cleaners biological safety cabinets
The gaseous agent ethylene oxide is typically used to sterilize all of the following EXCEPT ______.
human tissue
Metal compounds typically kill microbes by ______. disrupting the cell wall causing mutations in DNA inactivating enzymes and other proteins producing toxic radicals disrupting the cell membrane
inactivating enzymes and other proteins
The two primary iodine preparations are_____________ and tinctures of iodine.
iodophors
What type of radiation has enough energy to remove electrons from atoms, thereby destroying DNA and damaging cytoplasmic membranes?
ionizing
Ozone ______.
is a strong oxidizing agent
Ethylene oxide is gaseous agent that ______.
is very useful for sterilizing heat- or moisture-sensitive items.
One of the advantages of chlorine dioxide over other chlorine-releasing compounds is that ______.
it does not react with organic materials to form toxic products
All of the following are characteristics of bleach, a solution of sodium hypochlorite, EXCEPT ______? it is only effective against a limited range of microorganisms it reacts with some organic compounds to form trihalomethanes it is corrosive and toxic its germicidal activity is disrupted by organic compounds it reacts with some organic compounds to form carcinogens it is irritating to skin and mucous membranes
it is only effective against a limited range of microorganisms
All of the following are characteristics of bleach, a solution of sodium hypochlorite, EXCEPT ______? it reacts with some organic compounds to form carcinogens it is corrosive and toxic it is irritating to skin and mucous membranes its germicidal activity is disrupted by organic compounds it is only effective against a limited range of microorganisms it reacts with some organic compounds to form trihalomethanes
it is only effective against a limited range of microorganisms
Chemical agents that can destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses, are called___________ -level disinfectants.
low
Paper-thin membrane filters called________contain pore sizes so small they will trap microbes from liquids as they pass through.
microfilters
Many germicides lose their effectiveness in the presence of ______.
organic matter
Halogens are highly reactive _______ agents that _______.
oxidizing; cause damage to proteins
A brief heat treatment that reduces the number of spoilage organisms and destroys pathogens is called_________________.
pasteurization
Which of the following is a brief heat treatment used to prevent spoilage of wine without changing its flavor?
pasteurization
The chemical ortho-_______ provides an alternative to glutaraldehyde because it is less irritating on the eyes. However, it does stain skin proteins gray.
phthalaldehyde
High-______________ processing (HPP) is used to decrease the number of microbes in food while maintaining the color and flavor.
pressure
High pressure (130,000 psi) is thought to kill microbes by altering their ______.
proteins cell membranes
Ionizing radiation causes indirect tissue damage by reacting with O2 to produce___________________ oxygen______________(ROS).
reactive; species
Of all the metals, ______ is one of the few still used as a disinfectant.
silver
All of the following are examples of electromagnetic radiation EXCEPT ______.
sound waves
Manufacturers of germicidal chemicals must register with either the FDA and EPA in order to document ______.
the potency of their product
The effectiveness of germicidal chemicals depends upon ______.
the presence of organic matter the concentration used
It is important to destroy all endospores of Clostridium botulinum in commercial canning because ______.
the spores can germinate in canned foods and vegetative cells can produce botulinum toxin
Microwave ovens are not reliable for killing microbes in food because ______.
they often heat food unevenly
Alcohol-based solutions of certain antimicrobial chemicals like iodine are called____________________ .
tinctures
Boxed juices and single-serving containers of half-cream served in restaurants require no refrigeration because they have been ______.
treated with the ultra-high-temperature (UHT) method of processing, or "ultra-pasteurization"
True or false: Germicides are generally somewhat toxic to humans and the environment.
true
A disadvantage of using ionizing radiation to sterilize food is ______.
unwanted flavor changes
Germicidal chemicals ______.
usually react irreversibly with proteins, DNA, cytoplasmic membranes, or viral envelopes are often poorly understood with regards to mechanisms of action
Electromagnetic radiation is an invisible form of energy that travels in_________________ .
waves
Chlorine-releasing compounds such as sodium hypochlorite (bleach is a 5.25% solution) are used for all of the following EXCEPT ______.
wound treatment and skin cleansing
