Microbio Chapter 8
Which of the following is not true regarding the decimal reduction time? A. It is the time taken to reduce the number of pathogens in a sample by one log cycle B. It is a measure of the effective concentration of disinfectant that kills within a specific time period C. The Z value is the temperature equivalent of the D value D. Once the number of organisms has been reduced to 10%, the killing may slow due to resistant strains that remain in the population
It is a measure of the effective concentration of disinfectant that kills within a specific time period
Which of the following would be most appropriate for removal of bacteria and some viruses from a liquid?
Membrane filter (< 0.1μm)
Which of the following is not a method of heat sterilization?
Pasteurization
A biological safety cabinet filters out more microorganisms than an N95 mask. T/F
T
Which of the following lacks sufficient penetrating power for bulk sterilization?
Ultraviolet (UV) radiation at 260 nm
Which of these is a sterilizing gas?
ethylene oxide
Which kind of sterilization procedure takes advantage of the size of microorganisms?
filtration
Which of these techniques sterilizes on the basis of the size of the microbes to be removed?
filtration
An agent that specifically kills fungi but not other kinds of microorganisms is also known as a _________.
fungicidal agent
Which of the following would be most effective and practical for routine home disinfection of a toothbrush between uses?
hydrogen peroxide
Iodine can be complexed with an organic carrier to form water-soluble, stable complexes called __________, which release iodine slowly and eliminate skin burns and irritation associated with iodine use.
iodophors
A Z value has units of __________.
temperature
Which of the following is/are advantages of using bacteriophage to treat human bacterial infections?
-Bacteriophage can kill the bacteria. -Bacteriophage will not cause disease or harm humans. -Bacteriophage are very specific for the target bacteria and won't affect normal microbiota.
Check which of the following organisms/agents have been demonstrated to kill bacteria.
-Bacteriophages -Bdellovibrio bacteria
Which of the following is a function of pasteurization?
-Killing pathogenic microorganisms -Reducing the total microbial population -Increasing the shelf life of the product
Which of the following practices do you expect to see in a commercial establishment dedicated to body piercing?
-Needles are factory-sterilized and used for only a single customer before disposal. -The piercing environment is sanitized daily by wiping counters and furniture with a strong disinfectant.
Which describes the benefit of using bacteriophages to control microbes?
Bacteriophages release lysins to destroy bacteria.
Which of the following inhibits bacterial growth but does not kill bacteria?
Bacteriostatic agent
Which of the following is a Gram-negative bacterium that acts as a predator on other Gram-negative bacteria, and might be used to control populations of Gram-negative human pathogens in locations such as poultry farms?
Bdellovibrio
Which describes the benefit of using Bdellovibrio bacteria to control microbes?
Bdellovibrio bacteria are predators of Gram-negative pathogens such as Salmonella spp., Shigella spp., and E. coli.
Disinfectants are generally regulated by the _________.
Environmental Protection Agency
Alcohols are widely used as antiseptics and disinfectants because they are effective against endospores as well as vegetative cells. T/F
F
All germicides are capable of killing all pathogenic organisms and endospores. T/F
F
Bacteriophage therapy was developed after antibiotics were first discovered and used for treating bacterial infections. T/F
F
Because filtration removes rather than destroys microorganisms, it does not truly sterilize the materials passing through the filter. T/F
F
Dry heat methods usually require lower temperatures and shorter exposure times than moist heat methods to achieve the same degree of killing because of the drying effects of this form of heat. T/F
F
If one left a "pasteurized" flask of broth for a long time at room temperature, it would stay sterile forever, at least in principle. T/F
F
Antiseptics are generally regulated by the _________.
Food and Drug Administration
The type of filter used in a laminar flow biological safety cabinet is called a(n) __________ filter.
HEPA
Which best describes how heat controls microbes?
Heat denatures proteins and nucleic acids
Which statement best parallels the observation: when a new predator enters an ecosystem then the prey organisms are significantly stressed (i.e., killed).
Introduction of bacteriophages into the body to treat an infection
Several new materials have been developed for use in the microbiology lab. These materials must be sterilized before use, but cannot withstand a temperature over 60oC and can't be exposed to water. Which method of sterilization would be applicable?
Ionizing radiation
Which of the following is true about membrane filters?
It can't be depended on to remove all viruses from liquids.
Fecal transplants have been successfully used to treat Clostridioides difficile colitis by reintroducing healthy fecal microbiota that outcompete the C. difficile. T/F
T
Heavy metals are effective antimicrobial agents but are not widely used because of their high toxicity to humans. T/F
T
Heavy metals may inactivate proteins by reacting with their sulfhydryl groups. T/F
T
Microorganisms show differential sensitivity to antimicrobial agents. T/F
T
The rate of killing by an antimicrobial agent may slow when the microbial population has been greatly reduced because the remaining population may have a high proportion of resistant organisms. T/F
T
Ultraviolet radiation is an effective means of sterilizing surfaces. T/F
T
Which of the following represents the best definition for microbial death?
The organism will not grow on a medium that normally supports its growth.
If you design a new compound that inhibits the growth of bacteria then you would call it bacteriostatic. What would you call a compound that kills the bacteria?
bacteriocide
Bacterial pathogens may be controlled by ___________, which are viruses that specifically infect and lyse the bacterial host.
bacteriophages
An agent that prevents the growth of bacteria without causing irreversible damage to the bacteria is referred to as __________.
bacteriostatic
Which microbial control method best describes how an autoclave sterilizes material?
by heat
The disinfectant of choice for municipal water supplies is __________.
chlorine
Which of the following would be most effective and practical for routine home disinfection of a kitchen sponge between uses?
chlorine bleach
Although heavy metals are no longer widely used as germicides, __________ is an effective algicide in lakes and swimming pools.
copper sulfate
The time required to kill 90% of the microorganisms or spores in a sample at a specified temperature is the _________.
decimal reduction time (D value)
Moist heat sterilizes by _________.
denaturing protein
Which filtration design would be best suited for removing the majority of microbes and not clogging/slowing your filtration system too much?
depth filter
Amphipathic organic molecules that serve as disinfectants by disrupting membranes and denaturing proteins are called _________.
detergents
The substantial reduction of the total population of microorganisms on inanimate objects and the destruction of potential pathogens is called _________.
disinfection
The two most important alcohol germicides are __________ and __________.
ethanol; isopropanol
Which antimicrobial control method is best suited for heat-sensitive items such as disposable plastic Petri dishes and syringes?
ethylene oxide
Which of the following is (are) a sterilizing gas(es) that can be used on heat-sensitive materials?
ethylene oxide
Which of these is an agent that is used to sterilize the plastic tubing of heart-lung machines?
ethylene oxide
What is the best form of microbial control you could use for purifying a protein from genetically modified E. coli?
filtration
Which microbial control method best describes the process of pasteurization?
heat
Which antimicrobial control method is best suited as an antiseptic and noncorrosive for surgical plastics?
iodophors
Gamma radiation _________.
is used to sterilize some food products
Pasteurization is used to _________.
kill any pathogens present and retard spoilage
Sterilization involves __________ all viable microorganisms.
killing OR removing
When antiseptics and disinfectants are compared, antiseptics are generally _________.
less toxic
The disinfectant action of phenol and phenolic derivatives mainly is due to _________.
membrane damage and protein denaturation
Depth filters work differently than membrane filters to sterilize fluids. The difference is that _________.
membrane filters have smaller pores, but depth filters have complex passages that retain microbes while letting the fluid through. Both methods are efficient
The higher the phenol coefficient value, the _______ effective the disinfectant under the test conditions.
more
The use of bacteriophage to treat human infections is referred to as ________ __________.
phage therapy
The disinfectant screening method that is known as the ________ _________ test, is used to measure the potency of a disinfectant.
phenol coefficient
The disinfecting properties of Lysol, a common household disinfectant, depend upon the presence of __________.
phenolics
What is the best form of microbial control you could use for a soft, plastic, surgical device that will melt at high temperatures?
radiation
Which of the following environmental factors generally do(es) not have an impact on the efficiency of an antimicrobial agent?
refractive index
Joseph Lister _________.
revolutionized surgery by introducing phenol as a disinfectant
The reduction of the microbial population to levels that are considered safe by public health standards is called _________.
sanitization
Choose the characteristic of a microbe that would allow it to be controlled by filtration.
size of microbe
When comparing dry heat and moist heat sterilization, dry heat is _________.
slower
A(n) __________ is a chemical that can be used to sterilize materials.
sterilant
The destruction or removal of all viable organisms is called _________.
sterilization
A D value has units of __________.
time
The first product to be commercially treated by pasteurization was _________.
wine
In 2015, it was reported that several patients at UCLA medical center were infected with carbapenem-resistant Enterobacteriaceae (CRE) because of ineffective sterilization of equipment used for colonoscopy procedures. Which two of the following are important considerations when addressing this sterilization issue?
-The complexity of the equipment and the need to disassemble multiple components for cleaning present challenges for disinfection. -Organic matter like tissue samples must be removed before applying a disinfectant.
Which of the following influence(s) the efficiency of an antimicrobial agent?
-concentration of the agent -duration of exposure -temperature
Check all the ways heat can be used to control microbes.
-denatures proteins -denatures nucleic acid -disrupts membranes
Which chemical agents will denature proteins?
-phenols -alcohols -halogens
Larger populations generally are killed as rapidly as smaller populations. T/F
F
An agent that kills bacteria is referred to as __________.
bactericidal
Using the decimal reduction time (D-value) method, how many organisms would be left after one decimal reduction if you started with 1,000 bacteria?
100
Choose the best description of how filtration works to control microbes.
A filter is a solid material containing small holes that only allows liquids to pass but restricts larger substances from passing to a sterile environment.
Which will require a longer time to kill?
A larger population of microorganisms
Portable UV room sterilizing units are being used to reduce endospores of Clostridioides difficile in hospital rooms after patients have vacated. Which of the statements best describes this application?
UV radiation will destroy C. difficile endospores assuming it is applied for a long enough period and directly contacts all surfaces.
The prevention of infection caused by microorganisms is called _________.
antisepsis
Which of the following is MOST effective against resistant endospores?
autoclaving
Moist heat sterilization at 100°C kills all of the following EXCEPT _________.
bacterial endospores
