Chapter 11 Microbiology

The shortest length of time required to kill all test microbes at a specified temperature is the thermal death point. True or False

False

A drug destroys the peptidoglycan molecules of a bacterial cell. Which of the four main targets is affected in this scenario? a) Cell wall b) Proteins c) Cell membrane d) Cellular synthesis

a) Cell wall

Select the major cellular targets of physical and chemical control agents. Check all that apply a) Cell wall b) Flagella c) Cell membrane d) Proteins e) Microcompartments

a) Cell wall b) Flagella c) Cell membrane d) Proteins e) Microcompartments (all of them)

Select the methods that illustrate the use of moist heat to control microbes. Check all that apply. a) Steam autoclave b) Incineration c) Pasteurization d) Desiccation e) Boiling water

a) Steam autoclave b) Incineration c) Pasteurization d) Desiccation e) Boiling water (all of them)

Select the characteristics of a chemical control agent that make it a desirable agent. Check all that apply. a) Corrosive to metals and plastics b) Water or alcohol soluble and stable c) "-cidal" to a wide range of microbes, but nontoxic to humans and animal tissue d) Rapidly effective in low concentrations e) Ineffective in the presence of organic matter f) Inexpensive g) Short-lived, spontaneously inactivates with time

b) Water or alcohol soluble and stable c) "-cidal" to a wide range of microbes, but nontoxic to humans and animal tissue d) Rapidly effective in low concentrations f) Inexpensive

HEPA filters are used to remove microbes from a) medical instruments. b) air. c) human tissues. d) All of the choices are correct. e) liquids.

b) air.

Select the microorganism that is least resistant to chemical and physical control measures. a) Gram-positive bacteria b) Gram-negative bacteria c) Protozoan cysts d) Non-enveloped (naked) viruses e) Enveloped viruses

e) Enveloped viruses

Bacteriostatic agents kill bacterial cells. True or False

False

Desiccation is a form of physical control of microorganisms that can be used in moist or dry forms. True or False

False

Nonionizing radiation exhibits good penetrating power and can be used for cold sterilization. True or False

False

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature. True or False

False

Surgeons preparing for an invasive surgical procedure will scrub their hands thoroughly, and then they use a strong alcohol-based hand sanitizer which renders their hands sterile. True or False

False

Cationic detergents are surface active agents, also known as ______, which damage bacteria by binding bacterial surface proteins and disrupting ______. a) surfactants; cell membranes b) aqueous solutions; flagellar action c) peroxides; capsules d) tinctures; ribosomes

a) surfactants; cell membranes

A method for sterilizing milk, called _____ treatment, uses 134°C for 1 to 2 seconds a) flash pasteurization b) pasteurization c) tyndallization d) ultra high temperature e) batch pasteurization

d) ultra high temperature

Which of the following is not used as an antiseptic? a) Merthiolate b) Chlorhexidine c) 3% hydrogen peroxide d) Iodophor e) Aqueous glutaraldehyde

e) Aqueous glutaraldehyde

Ozone is a very effective disinfectant. True or False

True

Pasteurization does not inactivate endospores or thermoduric microbes. True or False

True

Select all of the statements that accurately reflect the process of filtration a) Filtration can be effectively used to remove microbial contaminants from solid materials. b) Filters, charcoal, and diatomaceous earth can all be used to remove microbial contaminants in the process of filtration. c) Filters with pores of the smallest diameter are utilized to sterilize air and liquid samples. d) Filtration is beneficial in the preparation of products, such as serum, that cannot withstand high heat. e) Filtration can effectively remove even soluble toxins in a pharmaceutical grade drug preparation.

a) Filtration can be effectively used to remove microbial contaminants from solid materials. c) Filters with pores of the smallest diameter are utilized to sterilize air and liquid samples. d) Filtration is beneficial in the preparation of products, such as serum, that cannot withstand high heat.

Evaluate the statements below, and select those that correctly apply to the use of radiation as a microbial control mechanism. Check all that apply. a) The use of radiation to control microbial growth comes in two forms; ionizing and nonionizing radiation. Of the two, ionizing radiation is the most destructive. b) Nonionizing radiation involves electrons being bombarded with enough energy to eject them from their atoms. Gamma rays are an example of this. c) Nonionizing radiation, e.g., UV light, causes electrons to make a quantum leap to an orbital with a higher energy state, which causes thymine dimers to form, but does not create ions. d) Ionizing radiation involves electrons being bombarded with enough energy to eject them from their atoms. X rays are an example of this. e) The use of radiation to control microbial growth comes in two forms; ionizing and nonionizing radiation. Of the two, nonionizing radiation is the most destructive.

a) The use of radiation to control microbial growth comes in two forms; ionizing and nonionizing radiation. Of the two, ionizing radiation is the most destructive. c) Nonionizing radiation, e.g., UV light, causes electrons to make a quantum leap to an orbital with a higher energy state, which causes thymine dimers to form, but does not create ions. d) Ionizing radiation involves electrons being bombarded with enough energy to eject them from their atoms. X rays are an example of this.

The minimum sterilizing conditions in a steam autoclave are a) 160°C for 2 hours. b) 121°C at 15 psi for 15 minutes c) 71.6°C for 15 seconds. d) 63°C for 30 minutes. e) 100°C for 30 minutes

b) 121°C at 15 psi for 15 minutes

Which of the following items are typically irradiated in order to kill microbes? a) Surgical gloves b) All of the choices are correct c) Cured meats d) Operating room air e) Human tissues such as heart valves and skin

b) All of the choices are correct

The cell can no longer regulate the passage of materials in and out of the cell. Which of the four main targets is affected in this scenario? a) Cell wall b) Cell membrane c) Proteins d) Cellular synthesis

b) Cell membrane

Dry heat a) includes tyndallization. b) is less efficient than moist heat. c) is used in devices called autoclaves. d) will sterilize at 121°C for 15 minutes. e) cannot sterilize.

b) is less efficient than moist heat.

Select the dry heat method of microbial control from the following examples. a) Autoclaving b) Boiling c) Incineration d) Desiccation

c) Incineration

The native state of certain enzymes are destroyed by heat, and the active sites are no longer able to bind with substrate. Which of the four main targets is affected in this scenario? a) Cellular synthesis b) Cell membrane c) Proteins d) Cell wall

c) Proteins

Choose the statement that identifies the major disadvantage of both cold and desiccation in terms of microbial control. a) These methods are technically difficult and labor-intensive. b) These methods produce harmful by-products and are costly. c) These methods are bacteriostatic rather than bactericidal. d) These methods may encourage growth of microbial populations.

c) These methods are bacteriostatic rather than bactericidal.

A(n) ______ agent would be used to destroy bacteria on a countertop whereas a(n) _______ agent would be used on skin prior to making an incision. a) antiseptic; sterilant b) disinfectant; sterilant c) disinfectant; antiseptic d) antiseptic; disinfectant

c) disinfectant; antiseptic

The lowest temperature required to kill all microbes in a sample within 10 minutes is the thermal death _____. a) time b) pathway c) point d) rate

c) point

What instrument is most effective for pressure-temperature sterilization? a) Oven b) Incubator c) Water-bath d) Autoclave e) Bunsen burner

d) Autoclave

Thymine dimers are formed in DNA, preventing replication. Which of the four main targets is affected in this scenario? a) Proteins b) Cell membrane c) Cell wall d) Cellular synthesis

d) Cellular synthesis

Select the phrase that describes the antimicrobial activity of alcohols. a) Destruction of endospores b) Interfere with nucleic acid replication and transcription c) Disrupt peptidoglycan structure d) Disrupt membrane lipids and denature proteins

d) Disrupt membrane lipids and denature proteins

_____ is a control method that removes microorganisms rather than inhibiting or killing them. a) Radiation b) Sterilization c) Disinfection d) Filtration e) Boiling

d) Filtration

What represents a nonionizing form of radiation, often used for disinfection purposes? a) Gamma rays b) Cathode rays c) X rays d) UV radiation

d) UV radiation

In lab, inoculating loops are sterilized using ______. a) gas sterilization b) moist heat c) filtration d) incineration e) chemicals

d) incineration