Microbiology: Chapter 11

The minimum sterilizing conditions in a steam autoclave are A. 100°C for 30 minutes. B. 63°C for 30 minutes. C. 71.6°C for 15 seconds. *D. 121°C at 15 psi for 15 minutes. E. 160°C for 2 hours.

121°C at 15 psi for 15 minutes.

Alcohols A. denature proteins when in a 50-95% alcohol-water solution. B. disinfect items when soaking method is utilized. C. are skin degerming agents. D. at 50% or higher concentrations dissolve cell membrane lipids. *E. All of the choices are correct.

All of the choices are correct.

Hydrogen peroxide is A. sporicidal. B. fungicidal. C. bactericidal. D. virucidal. E. All of the choices are correct.

All of the choices are correct.

What instrument is most effective for pressure-temperature sterilization? *A. Autoclave B. Oven C. Bunsen burner D. Water-bath E. Incubator

Autoclave

Which of the following microbial forms has the highest resistance to physical and chemical controls? A. Naked viruses B. Protozoan cysts C. Fungal spores *D. Bacterial endospores E. Yeast

Bacterial endospores

Which is correct regarding the rate of microbial death? A. Cells die at increasingly greater rates. B. Only older cells die in a culture. *C. Cells in a culture die at a constant rate. D. Upon contact with the control agent, all cells die at one time. E. Cells become metabolically inactive but are never killed.

Cells in a culture die at a constant rate.

Which of the following is true regarding the use of osmotic pressure as an antimicrobial agent? A. Salts and sugars external to a microbe create a hypotonic environment, which causes lysis of the cell. B. Salt is an effective solute to create an osmotic pressure gradient outside of a cell; however, the use of sugar, such as in jams and jellies, works via a different mechanism. C. Exposing organisms to the air on a benchtop so they completely dry out is an example of using osmotic pressure as a means of microbial control. *D. Exposing a microbe to a hypertonic environment draws water out of the cell, causing plasmolysis.

Exposing a microbe to a hypertonic environment draws water out of the cell, causing plasmolysis.

Chlorine compounds remain stable and effective in the presence of excess organic matter. True or False.

False

Isopropyl alcohol wiped across a skin site can sterilize it. 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

_____ is a control method that removes microorganisms rather than inhibiting or killing them. A. Disinfection B. Radiation *C. Filtration D. Sterilization E. Boiling

Filtration

Which of the following is not true of glutaraldehyde? A. It cross-links proteins on cell surfaces. B. It inactivates endospores in 3 hours. C. It does not damage plastics. *D. It is classified as a carcinogen. E. It inactivates viruses.

It is classified as a carcinogen.

Which antimicrobial method does not sterilize? A. Autoclave B. Ionizing radiation C. Ethylene oxide gas *D. Pasteurization

Pasteurization

Which of the following acids is not used to destroy or inhibit microbial cells in food? A. Benzoic acid B. Acetic acid C. Propionic acid *D. Phosphoric acid E. Lactic acid

Phosphoric acid

Which of the following represents the use of osmotic pressure as a microbial control method? *A. Salting of meat B. Bleaching a kitchen counter C. Rinsing of a cut with Betadine D. Exposing dental equipment to UV light

Salting of meat

You have some old plastic Petri dishes that you would like to use for pouring bacteriological agar plates. The only method of physical sterilization is ultraviolet radiation sterilization with your UV light (you cannot use the autoclave because it will disfigure and melt the plastic). After sterilizing the plates, pouring the sterilized agar medium, and then leaving the plates out at room temperature for a day or two to let them solidify and dry, you find contaminating bacterial colonies growing on the agar. Predict what has happened in this situation. A. Air got into the poured agar plates, contaminating them. B. The agar had bacteria in it, even after sterilization in the autoclave. C. The room temperature enhanced the growth of normal biota of the agar. *D. The lids of the Petri dishes were inadvertently left on while being sterilized.

The lids of the Petri dishes were inadvertently left on while being sterilized.

Your friend Joe recently visited the doctor for steroid injections into his knee to reduce swelling due to a previous knee injury. Within a couple of days, he had an infection caused by Pseudomonas, a very pathogenic and drug resistant bacterium. Luckily, Joe went to the doctor immediately and received antibiotics. The doctor tells him that the same problem has occurred to many other people across the United States. Predict the most likely cause of this situation. A. The bacterium is normally on the skin of people, so can easily access the patient's blood during the needle stick. B. The needles were re-used and already contaminated before being used on the patients. *C. The steroid was contaminated at the production plant, so multiple batches of that drug made at that plant were contaminated with that bacterium. D. The staff giving the steroid injections did not use proper aseptic technique.

The steroid was contaminated at the production plant, so multiple batches of that drug made at that plant were contaminated with that bacterium.

Which of the following is not true of chloramines? A. They are safer than free chlorine. *B. They form trihalomethanes with organic compounds. C. They contain chlorine. D. They are used to treat wounds and skin surfaces. E. They can sanitize and disinfect.

They form trihalomethanes with organic compounds.

Which of the following is not a heavy metal? *A. Tincture of iodine B. Merthiolate C. Silver nitrate solution D. Zinc E. Mercurochrome

Tincture of iodine

Alcohols are more effective at inactivating enveloped viruses than naked viruses. True or False.

True

Aniline dyes like crystal violet have antimicrobial activity particularly against gram-positive bacteria and some fungi. True or False.

True

Hydrogen peroxide is used in the process of sterilizing instruments such as endoscopes. True or False.

True

Ionizing radiation is more effective than nonionizing radiation in killing or inactivating microbes. True or False.

True

Organisms in the genus Pseudomonas are resistant to quats. True or False.

True

Ozone is a very effective disinfectant. True or False.

True

Prions require more extensive methods of sterilization than are needed for bacterial endospores. True or False.

True

_____ radiation excites atoms to a higher energy state within molecules such as DNA, which leads to the formation of pyrimidine dimers. *A. Ultraviolet B. Particle C. Ionizing D. Infrared E. Gamma

Ultraviolet

You have inherited some old glass baby milk bottles from your grandmother, and you would like to use them instead of plastic bottles. The bottles are placed into a large metal container and placed in the oven at 325oF for about 2 hours. What factor would you change if you wanted the sterilization to occur much quicker? *A. Use a pressure cooker to sterilize the bottles with steam B. Increase the temperature of the oven by 5 degrees C. Place the bottles outside in the sunlight and then place in the oven D. Pour an antimicrobial chemical into the bottles before placing into the oven

Use a pressure cooker to sterilize the bottles with steam

Agents that can denature microbial proteins include all of the following except ______. A. moist heat B. alcohol C. acids D. metallic ions *E. X rays

X rays

HEPA filters are used to remove microbes from *A. air. B. liquids. C. human tissues. D. medical instruments. E. All of the choices are correct.

air.

The alcohol wipe used on a patient's skin before an injection is an example of ______. *A. antisepsis B. disinfection C. sterilization D. decontamination E. sanitization

antisepsis

Placing organisms at 4oC is ______. A. bactericidal *B. bacteriostatic C. decontamination D. sterilization E. germicidal

bacteriostatic

Iodophors include ______. A. alcohols *B. betadine C. chloramines D. chlorhexidine E. tincture of iodine

betadine

The use of filtration for sterilization A. removes toxins. B. uses heat and filtration. C. relies on gravity. *D. can remove viruses. E. leaves behind endospores.

can remove viruses.

Scrubbing or immersing the skin in chemicals to reduce the numbers of microbes on the skin is ______. A. disinfection B. sterilization C. sanitization *D. degermation

degermation

Some microbial control agents are able to _____ cell proteins by breaking bonds that maintain the native state, the three-dimensional configuration of the proteins. A. mutate B. bind *C. denature D. dissolve

denature

Surfactants work by A. coating the organism preventing interaction with its environment. B. blocking transport into the organism. C. blocking transport out from the organism. *D. disrupting membrane integrity.

disrupting membrane integrity.

The sterilizing gas used in chemiclaves is ______. A. glutaraldehyde B. iodophor C. chlorine dioxide *D. ethylene oxide E. formaldehyde

ethylene oxide

Electrons are ejected from atoms in cells when organisms are exposed to ______. A. desiccation B. ultraviolet light C. ethyl alcohol D. hydrogen peroxide *E. gamma rays and X rays

gamma rays and X rays

The chemical agent/s that produce/s highly reactive hydroxyl-free radicals and also decomposes to O2 gas is ______. A. iodophors B. cationic detergents *C. hydrogen peroxide D. Cidex E. chlorhexidine

hydrogen peroxide

Cold temperatures are considered microbistatic, whereas excessive heat is considered microbicidal. This is due to the fact that *A. in cold temperatures, the energy of activation is not sufficient to drive chemical reactions regardless of the presence of enzymes, whereas excessive heat denatures enzymes and/or incinerates the cell causing irreparable damage. B. cold temperatures denature enzymes causing irreparable damage to the cell, whereas heat limits the energy of activation available to drive chemical reactions. C. cold temperatures freeze and therefore kill the cell, whereas excess heat keeps the cell metabolically active but not dividing. D. cold temperatures halt binary fission and is therefore considered a sterilant, whereas heat does not kill spores so it is not an effective method of control.

in cold temperatures, the energy of activation is not sufficient to drive chemical reactions regardless of the presence of enzymes, whereas excessive heat denatures enzymes and/or incinerates the cell causing irreparable damage.

All of the following act as surfactants except ______. A. alcohols B. soaps *C. iodine D. quaternary ammonia E. detergents

iodine

All of the following are alkylating control agents except ______. *A. iodophor B. ethylene oxide C. glutaraldehyde D. formaldehyde E. propylene oxide

iodophor

Microbial death occurs when there is A. no movement. *B. no reproduction. C. a change in appearance. D. a decrease in size. E. All of the choices occur.

no reproduction.

Pasteurization A. kills all vegetative forms. *B. reduces the number of vegetative forms. C. reduces the number of endospores. D. increases food nutrient value. E. is used to sterilize food products.

reduces the number of vegetative forms.

The method of removing vegetative microbial life forms and debris to reduce contamination to safe levels is termed ______. A. antisepsis B. disinfection C. sterilization D. decontamination *E. sanitization

sanitization

The process that destroys or removes all microorganisms and microbial forms, including bacterial endospores, on inanimate objects is ______. A. disinfection *B. sterilization C. antisepsis D. sanitization E. degermation

sterilization

The difference between thermal death time and thermal death point in microbicidal activity is that *A. thermal death time is the shortest amount of time required to kill an organism at a specific temperature, whereas thermal death temperature is the lowest temperature required to kill an organism in 10 minutes. B. thermal death time is the greatest amount of time required to kill an organism at a specific temperature, whereas thermal death temperature is the lowest temperature required to kill an organism in 10 minutes. C. thermal death time is the shortest amount of time required to kill an organism at a specific temperature, whereas thermal death temperature is the lowest temperature required to kill an organism in 30 minutes. D. thermal death time is the shortest amount of time required to kill an organism at a 100oC, whereas thermal death temperature is the lowest temperature required to kill an organism in 10 minutes.

thermal death time is the shortest amount of time required to kill an organism at a specific temperature, whereas thermal death temperature is the lowest temperature required to kill an organism in 10 minutes.