Textbook of Diagnostic Microbiology 4th Edition Test Bank Chapter 04: Control of Microorganisms MULTIPLE CHOICE
1. a. b. c. d.
The chemical or physical
... [Show More] method that destroys all forms of life is called: Sterilization
Disinfection Bacteriostatic Bactericidal ANS: A
Sterilization is the destruction of all forms of life, including bacterial spores. Disinfection is a process that eliminates a defined scope of microorganisms, including, in some cases, spores. Bacteriostatic inhibits the growth of microorganisms. Bactericidal kills bacteria.
REF: page 62 OBJ: Level 1 – Recall 2. a. b. c. 1 | P a g e
Organisms that are the most resistant to heat, chemicals, and radiation are: Parasites
Prions Bacteriad.
Viruses
ANS: B
Prions are naked pieces of protein, so they are harder to kill than any other organism. Viruses
usually contain a nucleic acid, and all the mentioned forms of killing can effectively disrupt their
nucleic acid. Bacteria and parasites are complete organisms that are killed by disinfection and
sterilization, even in the spore and cyst stages.
REF: page 63
OBJ: Level 1 – Recall
3. After using the phone, the laboratory tech sprayed the receiver with a chemical spray. This
process will kill a defined scope of microorganisms. What is this process called?
a.
b.
c.
d.
Sterilization
Bacteriostatic
Disinfection
Bactericidal
ANS: C
Sterilization kills all organisms and spores at a site. Bacteriostatic and bactericidal are adjectives that
describe the particular action of chemical agents: to inhibit bacterial growth or kill bacteria.
Disinfection kills a defined scope of microorganisms.
REF: page 62
OBJ: Level 2 – Interpretation
4. Before performing a phlebotomy, the phlebotomist will clean the area on a patient’s arm with a
2 | P a g esubstance before inserting the needle. This substance is called a(n):
Disinfectant
b.
c.
d.
Sterilizer
Antiseptic
Bactericidal
a.
ANS: C
A disinfectant is a chemical agent used to kill microorganisms on an inanimate object. To sterilize
is to kill all life; skin will still have organisms growing after wiping. Bactericidal is the process of
killing bacteria. An antiseptic is a substance applied to the skin for the purpose of eliminating or
reducing the number of bacteria present.
REF: page 62
OBJ: Level 2 – Interpretation
5. All the following factors play a significant role in the selection and implementation of the
appropriate method of disinfection EXCEPT:
a.
b.
c.
Temperature
Contact time
Biofilms
d. Humidity
ANS: D
3 | P a g eTemperature, contact time, and biofilms all play a role in selection and implementation of the
appropriate method of disinfection. Humidity is not important when attempting to disinfect or kill
organisms.
REF: pages 62-63 OBJ: Level 1 – Recall
6. When eliminating organisms from inanimate objects, higher numbers of organisms require
longer exposure times because:
a.
b.
c.
d.
All disinfecting agents are not alike and some require shorter times.
The chemical composition of the disinfecting agent varies.
Disinfecting agents containing carbon tetrachloride require longer times to act.
It takes longer to eliminate 99% of microorganisms.
ANS: D
When there are higher numbers of microorganisms, it takes longer to kill 99% of
microorganisms present. Although disinfectants are different, it still takes longer to kill more
organisms. The chemical composition of a disinfecting agent may affect the time required to kill
microorganisms, but microbial load is a determining factor.
REF: page 63
OBJ: Level 1 – Recall
7. When using disinfectants, it is important to follow the manufacturer’s instructions for diluting
the product because if it is not diluted properly:
a.
b.
c.
4 | P a g e
There may not be enough free chemicals to kill the organisms.
You would be wasting money by using too much disinfectant.
The resulting solution would not kill mycobacteria.d.
The resulting solution would not kill parasites.
ANS: A
The manufacturer tests disinfectants at a particular dilution, and this is the dilution needed for
optimum performance of the disinfectant. If the manufacturer’s instructions are not followed,
optimum effectiveness cannot be guaranteed.
REF: page 63
OBJ: Level 1 – Recall
8. If this is present on a surface to be disinfected, it can shield microorganisms from the
disinfectant or inactivate the disinfectant. What is this substance?
a.
b.
c.
Bleach (sodium hypochlorite)
Organic material
Hydrochloric acid
d. Water
ANS: B
Bleach, hydrochloric acid, and water can counteract another disinfectant, but they cannot shield
microorganisms from a disinfectant. Organic matter (e.g., blood, pus) can keep the disinfectant from
reaching and killing the microorganism.
REF: page 64
OBJ: Level 1 – Recall
5 | P a g e9.
a.
b.
When killing microorganisms, you must take all the following into consideration EXCEPT:
A type of microorganism
Temperature
c. Humidity
d.
Bioburden
ANS: C
The type of microorganism (bacteria, mycobacteria, parasite, etc.), the temperature, and the
bioburden (the number of bacteria) must be taken into consideration when decided how to best
kill microorganisms. The humidity plays no role in the killing of microorganisms.
REF: page 64
OBJ: Level 1 – Recall
10. Disinfectants are usually used at this temperature. a.
50° to 100° C
b.
c.
d.
0° to 10° C
25° to 50° C
20° to 22° C
ANS: D
Disinfectants are usually used at room temperature (20° to 22° C). Too high or too low a
temperature can actually inactivate a disinfectant.
6 | P a g eREF: page 64
OBJ: Level 1 – Recall
11.
a.
b.
Using two disinfectants to clean an area may actually do more harm than good. Why?
Two disinfectants may increase the amount of corrosion that occurs on a surface.
Two disinfectants may cause an adverse chemical reaction where a poisonous gas may be released.
c. When used together, two disinfectants may combine to sterilize a site instead of just disinfecting it.
d.
Two disinfectants may inactivate one another’s activity against microorganisms.
ANS: D
In many disinfectants, free ions are responsible for the killing activity of the solution. If two
solutions are mixed and one binds the free ions in the other solution, the microbial killing ability
terminates.
REF: page 64
OBJ: Level 2 – Interpretation
12.
a.
b.
c.
d.
Pasteurization achieves
Disinfection
Sterilization
Asepsis
Filtration
.
7 | P a g eANS: A
Pasteurization kills foodborne pathogens, but not microbial spores present in a liquid. Because
sterilization is killing of all microorganisms plus spores and cysts, pasteurization only disinfects.
Asepsis describes no bacteria present. Filtration describes another method of disinfection where
microorganisms are removed from a liquid by a physical device—a filter.
REF: page 65
OBJ: Level 1 – Recall
13.
a.
b.
c.
d.
Autoclaves use this method to sterilize inanimate objects.
Dry heat
Heat under steam pressure
Microwaves
Infrared light rays
ANS: B
Putting steam under 1 atmosphere of pressure achieves a temperature of 121° C. This
temperature and this pressure will kill all microorganisms except prions. Dry heat will not kill
spores or cysts.
Microwaves and infrared light rays are not used for sterilization or disinfecting objects.
REF: page 65
OBJ: Level 1 – Recall
14.
a.
Chemosterilizers exert their killing effect through all the following mechanisms EXCEPT:
Denaturation of cellular proteins
8 | P a g eb. Damage of RNA and DNA
c.
Inactivating enzyme substrates
d.
Reactions with components of the cytoplasmic membrane
ANS: C
If a chemical can denature proteins that are used by the cell, damage RNA or DNA, or react with
components of the cell membrane, they can damage the cell. Inactivating an enzyme substrate
may or may not have an effect on cellular function.
REF: page 66
OBJ: Level 1 – Recall
15.
a.
b.
c.
d.
Alcohols use this mechanism to inactivate microorganisms.
Denature proteins
Destroy DNA
Denature RNA
Inhibit cell wall synthesis
ANS: A
Alcohols do not have the capability to destroy DNA, denature RNA, or inhibit cell wall synthesis.
Instead, they disrupt the tertiary and quaternary structure of the cell wall proteins to destroy
microorganisms.
REF: page 67
9 | P a g e
OBJ: Level 1 – Recall16. A laboratory technician is working with tissue infected with Mycobacterium tuberculosis that
has been preserved in formalin for a couple years. After dissecting the tissue, how should the
worker sterilize the work area?
a.
b.
c.
d.
Wipe down the work area with a 37% formalin solution.
Wipe down the work area with a 10% bleach solution.
Wipe down the work area with a 50% alcohol solution.
Use formaldehyde gas to clean the area.
ANS: B
1.
tuberculosis can survive for years in formalized specimens. A powerful sterilizer is needed
to sterilize this area, and that is 10% bleach. Alcohol is not a sterilizer but rather an antiseptic.
Formaldehyde gas is used to disinfect biosafety hoods, but it is not a sterilizer.
REF: pages 67-68 OBJ: Level 3 – Synthesis
17.
The tech needs to sterilize a piece of equipment that cannot be autoclaved or gas
sterilized because the equipment contains lenses, metal, and rubber components. What
solution should be used to sterilize this piece of equipment?
a. 10% bleach
b. 37% formalin
c.
Glutaraldehyde
d. 90% alcohol
10 | P a g eANS: C
10% bleach cannot be used because it is a corrosive and can corrode metal; 37% formalin cannot
be used because it is a carcinogen, and the Occupational Safety and Health Administration (OSHA)
does not recommend it for routine sterilizing or disinfecting; 90% alcohol can be corrosive, but it
is also inactivated with any organic material that may be present on the instrument.
Glutaraldehyde is the sterilant of choice because it is not inactivated by organic material, and it
can kill both microbes and spores, depending on contact time.
REF: page 67
OBJ: Level 1 – Recall
18.
a.
b.
c.
d.
For the most effective microbial killing, all iodophors must be properly diluted because:
They stain the skin if too concentrated.
This decreases contact time for adequate killing.
There must be enough free iodine to kill the microorganisms.
This increases contact time for adequate killing.
ANS: C
When iodophors are used as skin preparations, contact time is essential for killing
microorganisms. Contact time does not depend on dilution. Iodophors are considered
nonstaining. The reason for diluting iodophors properly is that the dilution ratio is important to
ensure there is enough free iodine to kill microorganisms.
REF: page 68
OBJ: Level 1 – Recall
19.
Even though hypochlorites are inexpensive and have a broad range of microbes that
they kill, they are not used as sterilants because of:
a.
11 | P a g e
The corrosive nature of the compoundb.
c.
d.
The activation required by organic matter
Short exposure time for sporicidal action
Long exposure time for sporicidal action
ANS: D
Hypochlorites require a long exposure time to kill spores, and they are inactivated by organic
material present on an object. They are not used as a disinfectant because they are corrosive.
REF: page 68
OBJ: Level 1 – Recall
20.
Disinfectants containing heavy metal compounds have been replaced as
disinfectants, except for
, which is still used as a prophylactic treatment in
newborns to prevent gonococcal conjunctivitis.
Silver nitrate
b.
c.
d.
Copper sulfate
Ammonium nitrate
Mercuric chloride
a.
ANS: A
Mercuric chloride is a preservative used in parasitology. Copper sulfate is used to estimate the
amount of hemoglobin in a drop of blood. Ammonium nitrate is used as a component of
gunpowder. Silver nitrate is indeed used to swab the eyes of newborns to protect them from
gonococcal conjunctivitis.
12 | P a g eREF: page 69
OBJ: Level 1 – Recall
21.
Many materials in hospitals that must be sterilized cannot withstand steam sterilization.
Gas sterilization is used instead, using this gas.
a. Nitrous oxide
b.
Oxygen
c.
d.
Ethylene oxide
Carbon dioxide
ANS: C
Nitrous oxide, oxygen, and carbon dioxide are all gases, but they do not kill microbes or their
spores. Ethylene oxide is usually mixed with nitrogen or carbon dioxide before use because it is
explosive in its pure form. It is used in hospitals and in the manufacturing industry for sterilizing
thermoplastic products.
REF: page 70
OBJ: Level 1 – Recall
22.
a.
b.
c.
d.
Why should health care workers wash their hands after coming into contact with a patient?
To reduce the amount of red blood cells transmitted from one patient to the next
To reduce the occurrence of hemolytic transfusion reactions
To reduce the need for antiseptics and disinfectants
To reduce the spread of pathogenic bacteria from one individual to another
13 | P a g eANS: D
Any pathogenic bacteria present on the hands of one individual will be passed on to the next
individual unless the hands are washed to remove the pathogens. Hands visibly contaminated
with red blood cells are always washed after becoming soiled. Hemolytic transfusion reactions
are caused by the intravenous administration of red blood cells. Antiseptics and disinfectants will
always be needed to cleanse skin and inanimate objects to free them of pathogenic bacteria.
REF: page 71
OBJ: Level 1 – Recall
23.
a.
b.
c.
d.
High-level disinfectants are active against all the following EXCEPT:
Parasites
Spores
Fungi
Tubercle bacilli
ANS: A
High-level disinfectants are active against vegetative cells, tubercle bacilli, spores, fungi, and
viruses. These disinfectants have no activity against parasites.
REF: page 64
OBJ: Level 1 – Recall
24.
This agency regulates the use, sale, and distribution of antimicrobial pesticide products
for certain inanimate, hard, nonporous surfaces, or incorporated into substances under the
pesticide law.
a.
Antimicrobial Division of Environmental Protection Agency (EPA)
14 | P a g eb.
c.
d.
Centers for Disease Control and Prevention (CDC)
U.S. Army Medical Research Institute for Infectious Diseases (USAMRIID)
U.S. Food and Drug Administration (FDA)
ANS: A
The CDC acts as a clearinghouse for information of medically important bacteria and houses one
of two Biosafety Level 4 laboratories. The other Biosafety Level 4 laboratory is found at the Army
infectious disease research facility, USAMRIID. The FDA regulates substances that are put into
the body. The Antimicrobial Division of the EPA regulates the use of antimicrobials on inanimate,
nonporous surfaces.
REF: page 70
OBJ: Level 1 – Recall
25.
The disinfectant label should indicate several highlighted points important in selecting
the appropriate agents for designated use, including all the following EXCEPT:
a.
b.
c.
d.
Level of biocidal action
Alcohol content
The nature of microbial contamination
Structure and design of an item to be disinfected
ANS: B
The label of a disinfectant should include the structure and design of an item, active ingredient of
chemical, pH, hardness of water, exposure time, extent of precleaning, biocidal action, nature of
microbial contamination, requirements of chemical agents, kill time, composition of items to be
disinfected, and method of application.
15 | P a g eREF: pages 70-71 OBJ: Level 2 – Interpretation
26.
These two alcohols are effective in killing hepatitis B virus (HBV).
a. 50% isopropyl and 50% butanol
b. 95% propanol and 70% ethanol
c.
70% isopropyl and 95% ethanol
d. 70% pentanol and 70% isopropyl
ANS: C
The only two alcohols used in U.S. hospitals that kill HBV are 70% isopropyl and 95% ethanol.
REF: page 67
OBJ: Level 1 – Recall
27.
This chemical is a saturated 5-carbon dialdehyde that has broad-spectrum activity,
rapid killing action, and remains active in the presence of organic matter.
a.
b.
c.
d.
ANS: D
Formalin is designated as a carcinogen by the Occupational Safety and Health Administration
(OSHA), and worker exposure limits have been set. These adverse effects limit its usefulness.
Formaldehyde is a gas that is usually known as formalin. Haloaldehyde is not used as a
disinfectant. Glutaraldehyde is a good killing agent because it has broad-spectrum activity, rapid
16 | P a g e
Formalin
Formaldehyde
Haloaldehyde
Glutaraldehydekilling action, remains active in the presence of organic matter, and can be used on sensitive
equipment.
REF: page 67
OBJ: Level 2 – Interpretation
28.
These disinfectants are cationic, surface-activated agents that work by reducing the
surface tension of molecules in a liquid, resulting in the disruption of the cellular membrane of
microbes.
a.
b.
c.
d.
Quaternary ammonium compounds
Heavy metals
Chlorines
Iodophors
ANS: A
Heavy metals are bacteriostatic. The mechanism by which chlorines kill microorganisms is the
oxidative effects of hypochlorous acid. Iodophors kill through the action of periodic acid.
Quaternary ammonium compounds are disinfectants that are cationic, surface-activated agents
that disrupt the cellular membrane of microbes.
REF: page 68
OBJ: Level 2 – Interpretation
29.
a.
b.
c.
17 | P a g e
This organization regulates chemical skin antiseptics.
Environmental Protection Agency (EPA)
Food and Drug Administration (FDA)
Centers for Disease Control and Prevention (CDC)d. National Institutes of Health (NIH) ANS: B
The Antimicrobial Division of the EPA regulates disinfectants. The CDC is the nation’s clearinghouse on infectious diseases. The NIH is a conglomerate of special federal agencies that award research grants to further knowledge in a particular area. The FDA regulates chemical skin antiseptics. [Show Less]