MIC205A – Microbiology – Exam 2 Questions and Answers
Which of the following is NOT a sterilization method? Pasteurization
You have an unknown pathogen. Chemical analysis of the microbe indicates that it is composed
of DNA, RNA, lipid and protein. It also contains chitin. What would be the most appropriate
agent for destroying this pathogen? Fungicide
Select the statements about ionizing radiation that are TRUE. It can be used to sterilize
medication, it can be used to sterilize medical equipment, it can be used to reduce spoilage
organism on food
Match the important points regarding selection of an appropriate germicide with the
description/rationale that fits it best. Toxicity- All germicides are somewhat harmful to
humans and the environment. This parameter identifies HOW harmful the chemical is.
Storage and stability- Some germicides may lose efficiency over time, or may be required in
very large amounts that would make them impractical for frequent applications.
Cost and availability- Some germicides are highly effective, but are rare and/or expensive.
Compatibility with the material being treated- Some substances are negatively affected by
treatment with some germicides (i.e. corrosives damaging metals/rubber).
Activity in the presence of organic matter- Some germicides may become less efficient when
used in/on areas with organic matter.
Halogens Chlorine, chlorine dioxide, iodine; common disinfectant which oxidizes proteins
and other cell components
Quaternary Ammonium Compounds cationic detergent which can be safely used on food
preparation surfaces; compound reacts with membranes to destroy many vegetative bacteria
and enveloped viruses; these compounds are ineffective against mycobacteria, naked viruses
and pseudomonas species
,alcohols aqueous solutions which can kill vegetative bacteria and fungi but not bacterial
endospores or naked viruses; solutions can be used as antiseptics to to disinfect instruments
and surfaces without leaving a residue; ethanol or isopropanol
phenolic compounds Carbolic acid; Germicidal agent which can leave an antimicrobial
residue after use.
Which of the following concerns would lead a user to wash an item after it had been treated
with a germicide? Corrosive residue left after treatment.
Which of the following chemicals is/are suspected carcinogens? Formaldehyde
Ethylene oxide
Select the method that would be used to sterilize a liquid containing vitamin B12 and human
growth hormone. membrane filtration
Boiling is not a reliable method for sterilization because it does not destroy heat-resistant
endospores
Select the FALSE statements regarding the use of irradiation for sterilizing foods irritation
replaces the need for other food-safety techniques; irritated products are radioactive and
dangerous to eat; irritation introduces carcinogens into food
ionizing radiation High energy radiation that directly destroys DNA and damages cytoplasmic
membranes. It can also cause indirect damage by producing reactive oxygen species (ROS).
Microwaves Doesn't affect microorganisms directly, but can generate heat in fluids which
can indirectly kill microbes.
, Ultraviolet radiation Not very penetrating radiation. Easily stopped by interfering materials.
Works by producing thymine dimers in DNA strands. Most effective at close range and with
long duration of exposure.
Disinfection Reduction of most microbial life on inanimate surfaces
Preservation Slows microbial growth but does not reduce the number of existing microbes.
Sterilization Destruction of all microbial life
Decontamination Mechanical removal of most microbes from living or inanimate surfaces
Match the listed objects and compounds with the appropriate method used to destroy
microbes and viruses on/in them. Moist heat: culture media, milk
Dry heat: medical waste, inoculation loop, animal carcasses
Radiation: meat products, heat-sensitive medications
Chlorine is safely used to disinfect waste liquids, some medical instruments, and various
surfaces. It is readily available in liquid household bleach but bleach must be diluted because
high concentrations are toxic and corrosive. To obtain an effective concentration of chlorine
when using household bleach, a 1:100 dilution is made. This means that ______ mL of bleach is
added to ______ mL of water. 1.0/99
Why is autoclaving better than boiling for sterilizing microbiology equipment and media?
Autoclaves use pressurized steam, so can achieve a higher temperature than boiling water.
Which of the following is NOT a sterilization method? Pasteurization
You have an unknown pathogen. Chemical analysis of the microbe indicates that it is composed
of DNA, RNA, lipid and protein. It also contains chitin. What would be the most appropriate
agent for destroying this pathogen? Fungicide
Select the statements about ionizing radiation that are TRUE. It can be used to sterilize
medication, it can be used to sterilize medical equipment, it can be used to reduce spoilage
organism on food
Match the important points regarding selection of an appropriate germicide with the
description/rationale that fits it best. Toxicity- All germicides are somewhat harmful to
humans and the environment. This parameter identifies HOW harmful the chemical is.
Storage and stability- Some germicides may lose efficiency over time, or may be required in
very large amounts that would make them impractical for frequent applications.
Cost and availability- Some germicides are highly effective, but are rare and/or expensive.
Compatibility with the material being treated- Some substances are negatively affected by
treatment with some germicides (i.e. corrosives damaging metals/rubber).
Activity in the presence of organic matter- Some germicides may become less efficient when
used in/on areas with organic matter.
Halogens Chlorine, chlorine dioxide, iodine; common disinfectant which oxidizes proteins
and other cell components
Quaternary Ammonium Compounds cationic detergent which can be safely used on food
preparation surfaces; compound reacts with membranes to destroy many vegetative bacteria
and enveloped viruses; these compounds are ineffective against mycobacteria, naked viruses
and pseudomonas species
,alcohols aqueous solutions which can kill vegetative bacteria and fungi but not bacterial
endospores or naked viruses; solutions can be used as antiseptics to to disinfect instruments
and surfaces without leaving a residue; ethanol or isopropanol
phenolic compounds Carbolic acid; Germicidal agent which can leave an antimicrobial
residue after use.
Which of the following concerns would lead a user to wash an item after it had been treated
with a germicide? Corrosive residue left after treatment.
Which of the following chemicals is/are suspected carcinogens? Formaldehyde
Ethylene oxide
Select the method that would be used to sterilize a liquid containing vitamin B12 and human
growth hormone. membrane filtration
Boiling is not a reliable method for sterilization because it does not destroy heat-resistant
endospores
Select the FALSE statements regarding the use of irradiation for sterilizing foods irritation
replaces the need for other food-safety techniques; irritated products are radioactive and
dangerous to eat; irritation introduces carcinogens into food
ionizing radiation High energy radiation that directly destroys DNA and damages cytoplasmic
membranes. It can also cause indirect damage by producing reactive oxygen species (ROS).
Microwaves Doesn't affect microorganisms directly, but can generate heat in fluids which
can indirectly kill microbes.
, Ultraviolet radiation Not very penetrating radiation. Easily stopped by interfering materials.
Works by producing thymine dimers in DNA strands. Most effective at close range and with
long duration of exposure.
Disinfection Reduction of most microbial life on inanimate surfaces
Preservation Slows microbial growth but does not reduce the number of existing microbes.
Sterilization Destruction of all microbial life
Decontamination Mechanical removal of most microbes from living or inanimate surfaces
Match the listed objects and compounds with the appropriate method used to destroy
microbes and viruses on/in them. Moist heat: culture media, milk
Dry heat: medical waste, inoculation loop, animal carcasses
Radiation: meat products, heat-sensitive medications
Chlorine is safely used to disinfect waste liquids, some medical instruments, and various
surfaces. It is readily available in liquid household bleach but bleach must be diluted because
high concentrations are toxic and corrosive. To obtain an effective concentration of chlorine
when using household bleach, a 1:100 dilution is made. This means that ______ mL of bleach is
added to ______ mL of water. 1.0/99
Why is autoclaving better than boiling for sterilizing microbiology equipment and media?
Autoclaves use pressurized steam, so can achieve a higher temperature than boiling water.
