Question 1

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) Bleach (sodium hypochlorite)
B) Organic material
C) Hydrochloric acid
D) Water

Accepted Answer

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.

Question 2

Organisms that are the most resistant to heat,chemicals,and radiation are:
A) Parasites
B) Prions
C) Bacteria
D) Viruses

Accepted Answer

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.

Question 3

When eliminating organisms from inanimate objects,higher numbers of organisms require longer exposure times because:
A) All disinfecting agents are not alike and some require shorter times.
B) The chemical composition of the disinfecting agent varies.
C) Disinfecting agents containing carbon tetrachloride require longer times to act.
D) It takes longer to eliminate 99% of microorganisms.

Accepted Answer

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.

Question 4

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) Wipe down the work area with a 37% formalin solution.
B) Wipe down the work area with a 10% bleach solution.
C) Wipe down the work area with a 50% alcohol solution.
D) Use formaldehyde gas to clean the area.

Accepted Answer

M.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.

Question 5

For the most effective microbial killing,all iodophors must be properly diluted because:
A) They stain the skin if too concentrated.
B) This decreases contact time for adequate killing.
C) There must be enough free iodine to kill the microorganisms.
D) This increases contact time for adequate killing.

Accepted Answer

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.

Question 6

Using two disinfectants to clean an area may actually do more harm than good.Why?
A) Two disinfectants may increase the amount of corrosion that occurs on a surface.
B) 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.

Accepted Answer

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.

Question 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) There may not be enough free chemicals to kill the organisms.
B) You would be wasting money by using too much disinfectant.
C) The resulting solution would not kill mycobacteria.
D) The resulting solution would not kill parasites.

Accepted Answer

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.

Question 8

When killing microorganisms,you must take all the following into consideration EXCEPT:
A) A type of microorganism
B) Temperature
C) Humidity
D) Bioburden

Accepted Answer

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.

Question 9

Disinfectants are usually used at this temperature.
A) 50° to 100° C
B) 0° to 10° C
C) 25° to 50° C
D) 20° to 22° C

Accepted Answer

Disinfectants are usually used at room temperature (20° to 22° C).Too high or too low a temperature can actually inactivate a disinfectant.

Question 10

The chemical or physical method that destroys all forms of life is called:
A) Sterilization
B) Disinfection
C) Bacteriostatic
D) Bactericidal

Accepted Answer

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.

Question 11

Alcohols use this mechanism to inactivate microorganisms.
A) Denature proteins
B) Destroy DNA
C) Denature RNA
D) Inhibit cell wall synthesis

Accepted Answer

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.

Question 12

Even though hypochlorites are inexpensive and have a broad range of microbes that they kill,they are not used as sterilants because of:
A) The corrosive nature of the compound
B) The activation required by organic matter
C) Short exposure time for sporicidal action
D) Long exposure time for sporicidal action

Accepted Answer

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.

Question 13

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

Accepted Answer

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.

Question 14

Chemosterilizers exert their killing effect through all the following mechanisms EXCEPT:
A) Denaturation of cellular proteins
B) Damage of RNA and DNA
C) Inactivating enzyme substrates
D) Reactions with components of the cytoplasmic membrane

Accepted Answer

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.

Question 15

Autoclaves use this method to sterilize inanimate objects.
A) Dry heat
B) Heat under steam pressure
C) Microwaves
D) Infrared light rays

Accepted Answer

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.

Question 16

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) Sterilization
B) Bacteriostatic
C) Disinfection
D) Bactericidal

Accepted Answer

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.

Question 17

Before performing a phlebotomy,the phlebotomist will clean the area on a patient's arm with a substance before inserting the needle.This substance is called a(n):
A) Disinfectant
B) Sterilizer
C) Antiseptic
D) Bactericidal

Accepted Answer

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.

Question 18

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.
A) Silver nitrate
B) Copper sulfate
C) Ammonium nitrate
D) Mercuric chloride

Accepted Answer

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.

Question 19

All the following factors play a significant role in the selection and implementation of the appropriate method of disinfection EXCEPT:
A) Temperature
B) Contact time
C) Biofilms
D) Humidity

Accepted Answer

Temperature,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.

Question 20

Pasteurization achieves _____.
A) Disinfection
B) Sterilization
C) Asepsis
D) Filtration

Accepted Answer

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.

Quiz 4: Control of Microorganisms

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?

Organisms that are the most resistant to heat,chemicals,and radiation are:

When eliminating organisms from inanimate objects,higher numbers of organisms require longer exposure times because:

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?

For the most effective microbial killing,all iodophors must be properly diluted because:

Using two disinfectants to clean an area may actually do more harm than good.Why?

When using disinfectants,it is important to follow the manufacturer's instructions for diluting the product because if it is not diluted properly:

When killing microorganisms,you must take all the following into consideration EXCEPT:

Disinfectants are usually used at this temperature.

The chemical or physical method that destroys all forms of life is called:

Alcohols use this mechanism to inactivate microorganisms.

Even though hypochlorites are inexpensive and have a broad range of microbes that they kill,they are not used as sterilants because of:

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?

Chemosterilizers exert their killing effect through all the following mechanisms EXCEPT:

Autoclaves use this method to sterilize inanimate objects.

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?

Before performing a phlebotomy,the phlebotomist will clean the area on a patient's arm with a substance before inserting the needle.This substance is called a(n) :

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.

All the following factors play a significant role in the selection and implementation of the appropriate method of disinfection EXCEPT:

Pasteurization achieves _____.