Microbiology Ch 7 - The Control of Microbial Growth

Which of the following regarding antimicrobial control agents is false? A. Some agents inactivate viruses by attacking cell membrane lipids. B. Some agents affect microbial cell membranes by dissolving lipids. C. Contaminating organic debris such as blood or sputum decrease effectiveness. D. Some agents kill by denaturing microbial cell proteins. E. Silver is used for treating antibiotic-resistant bacteria.

A. Some agents inactivate viruses by attacking cell membrane lipids.

Which of the following shows the moist heat methods in order of the temperature used (highest to lowest)? A. Ultrahigh>Autoclave>Boiling>Batch Pasteurization B. Autoclave>Ultrahigh>Batch Pasteurization>Boiling C. Ultrahigh>Boiling>Autoclave>Batch Pasteurization D. Ultrahigh> Boiling>Batch Pasteurization >Autoclave

A. Ultrahigh>Autoclave>Boiling>Batch Pasteurization

Gluteraldehydes are among the most effective chemical control agents because they __________. A. are relatively safe, yet considered a sterilizing agent B. act as surfactants C. are oligodynamic D. are useful in preserving food

A. are relatively safe, yet considered a sterilizing agent Even in small concentrations, given adequate exposure time, gluteraldehydes inactivate microbial proteins and are considered bactericidal, tuberculocidal, virucidal, and sporicidal while being less irritating to living tissue. The fact that it is a liquid makes it an extremely versatile agent for a variety of hospital equipment.

All of the following substances are used to preserve foods EXCEPT A. biguanides. B. potassium sorbate. C. calcium propionate. D. nisin. E. sodium nitrite.

A. biguanides.

Which of the following disinfectants acts by disrupting the plasma membrane? A. bisphenols B. aldehydes C. heavy metals D. halogens E. soaps

A. bisphenols

Which of the following physical methods of microbial control denatures proteins as a mechanism of action? A. boiling or autoclaving B. incineration C. radiation D. osmotic pressure

A. boiling or autoclaving Heat denatures proteins by altering the tertiary structure, inhibiting their function.

Application of heat to living cells can result in all of the following EXCEPT A. decreased thermal death time. B. denaturation of enzymes. C. alteration of membrane permeability. D. damage to nucleic acids. E. breaking of hydrogen bonds.

A. decreased thermal death time.

Which of the following chemical agents is used for sterilization? A. ethylene oxide B. soap C. phenolics D. chlorine E. alcohol

A. ethylene oxide

All of the following are methods of food preservation EXCEPT A. microwaves. B. high pressure. C. desiccation. D. osmotic pressure. E. ionizing radiation.

A. microwaves.

Which one of the following is most resistant to chemical biocides? A. mycobacteria B. gram-negative bacteria C. protozoan cysts D. viruses with lipid envelopes E. gram-positive bacteria

A. mycobacteria

If you were preparing nutrient agar at home and did not have an autoclave, what could you use to sterilize the nutrient agar? A. pressure cooker at 121°C for 15 minutes B. boiling for 1 hour C. oven at 121°C for 1 hour D. hydrogen peroxide E. bleach

A. pressure cooker at 121°C for 15 minutes

When microbial control methods are used, microbes are destroyed at a constant rate; there is no instantaneous death of all the microbes present. That microbial death rate is influenced by all of the following factors EXCEPT __________. A. toxins produced by the microbe B. the microbial characteristics C. the number of microbes D. the time of exposure

A. toxins produced by the microbe Although microbial toxins may influence the status of an infection, these factors do not influence the death rate of the organism.

Which concentration of ethanol is the most effective bactericide? A. 100% B. 70% C. 50% D. 40% E. 30%

B. 70%

Which of the following is a limitation of the autoclave? A. It cannot be used with glassware. B. It cannot be used with heat-labile materials. C. It cannot inactivate viruses. D. It requires an excessively long time to achieve sterilization. E. It cannot kill endospores.

B. It cannot be used with heat-labile materials.

_______________ is a process used to destroy pathogens in food and drinks. It must be done at a lower temperature than other methods so that _______________. A. autoclaving; beneficial microorganisms are not killed B. Pasteurization; the taste of the food or drink will not be altered C. Pasteurization; beneficial microorganisms are not killed D. autoclaving; the taste of the food or drink will not be altered

B. Pasteurization; the taste of the food or drink will not be altered

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper? A. autoclave B. gamma radiation C. sunlight D. microwaves E. ultraviolet radiation

B. gamma radiation

Which of the following correctly lists, in increasing order, the resistance of microorganisms to chemical biocides? A. gram-negative bacteria, fungi, protozoan cysts, mycobacteria B. gram-positive bacteria, fungi, endospores, prions C. prions, gram-negative bacteria, vegetative protozoa, gram-positive bacteria D. protozoan cysts, fungi, gram-negative bacteria, prions

B. gram-positive bacteria, fungi, endospores, prions Gram-positive bacteria are the easiest to destroy, and prions are the most difficult to destroy.

Surface-active agents act by decreasing surface tension so that microbes can be more easily removed. All of the following agents use this mechanism of action EXCEPT __________. A. soaps and detergents B. halogens C. quaternary ammonium compounds (quats) D. acid-anionic sanitizers

B. halogens This is the exception. The mechanism of action for halogens includes inhibiting proteins and acting as a strong oxidizing agent, but halogens do not act as surface-active agents.

Ethylene oxide A. is not sporicidal. B. is a sterilizing agent. C. is the active chemical in household bleach. D. is a good antiseptic. E. requires high heat to be effective.

B. is a sterilizing agent.

Consider various effects of moist and dry heat to control microbial growth. Which of the following methods would best reduce microbes without altering the taste and chemical composition of beer? A. boiling B. pasteurization C. hot-air sterilization D. autoclaving

B. pasteurization Pasteurization retains the properties of the alcohol and the protein structure. Although it does not destroy all microbes, it is adequate to destroy most of the harmful microbes while retaining flavor.

A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In the table, which compound was the most effective against Staphylococcus? A B C D The answer cannot be determined.

C

Contaminated hospital equipment represents a difficult environment to control harmful microbial growth. Regarding influences that affect disinfection of hospital equipment, which of the following is an accurate statement? A. The presence of organic matter, such as dried blood or protein, will not affect the action of antimicrobial agents. B. Biofilms, often found contaminating hospital equipment, are relatively simple targets for biocides to reach effectively. C. The cell wall of gram-negative bacteria is especially resistant to many chemicals that are used destroy microbes. D. Antimicrobial agents work best under reduced temperatures.

C. The cell wall of gram-negative bacteria is especially resistant to many chemicals that are used destroy microbes. A principal factor in this relative resistance to biocides is the external lipopolysaccharide layer of gram-negative bacteria.

Which of the following pairs of terms is mismatched? A. germicide - kills microbes B. virucide - inactivates viruses C. bacteriostatic kills vegetative bacterial cells D. fungicide kills yeasts and molds E. sterilant destroys all living microorganisms

C. bacteriostatic kills vegetative bacterial cells

Evaluate the following chemical agents in regard to the effective use against endospores and mycobacteria. In a clinical situation where it is essential to control microbial growth that includes both mycobacteria and endospores, which chemical agent would be the most effective to guarantee the broadest disinfection? A. alcohols B. phenolics C. chlorines D. iodine

C. chlorines Chlorine has the best overall action against both of these targets.

Disinfection of water is achieved by all of the following EXCEPT A. ozone. B. UV radiation. C. peracetic acid. D. copper sulfate. E. chlorine.

C. peracetic acid.

During a flood, a community's well water system is contaminated with a pathogenic fungus. If the residents boil their water for 15 minutes prior to consumption, will they be protected? A. definitely not B. probably not C. yes, most likely

C. yes, most likely

Which of the following regarding antimicrobial control agents is false? A. Some agents kill by denaturing microbial cell proteins. B. Contaminating organic debris such as blood or sputum will decrease effectiveness. C. Some agents are utilized as both an antiseptic and a disinfectant. D. A true antimicrobial control agent is equally effective against both bacteria and viruses. E. Some agents affect microbial cell membranes by dissolving lipids.

D. A true antimicrobial control agent is equally effective against both bacteria and viruses.

Which of the following treatments is the most effective for controlling microbial growth? A. 63°C for 30 minutes B. 72°C for 15 seconds C. 140°C for 4 seconds D. They are equivalent treatments. E. None of the answers is correct.

D. They are equivalent treatments.

Prior to drawing blood for a blood donation, the nurse will scrub the arm with a Betadine solution. This form of antimicrobial control would be called __________. A. sterilization B. disinfection C. sanitization D. antisepsis

D. antisepsis

All of the following are effective for destroying prions EXCEPT A. proteases. B. incineration. C. NaOH + autoclaving at 134°C. D. boiling. E. Each of the answers will destroy prions.

D. boiling.

An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n) A. aseptic. B. virucide. C. antiseptic. D. disinfectant. E. fungicide.

D. disinfectant.

Microbial control methods usually target any of the following microbial structuresEXCEPT which one? A. plasma membrane permeability B. nucleic acids C. microbial proteins D. mitochondria

D. mitochondria Most of the target organisms are bacteria or viruses, which do not contain mitochondria. In addition, microbial control mechanisms attempt to target structures in microbes that are not common to human cells.

Bone and tendons for transplant are decontaminated by A. peroxygens. B. glutaraldehyde. C. ethylene oxide. D. supercritical fluids. E. plasma sterilization.

D. supercritical fluids.

The antimicrobial activity of chlorine is due to which of the following? A. the formation of a hypochlorite ion B. disruption of the plasma membrane C. the formation of ozone D. the formation of hypochlorous acid E. the formation of hydrochloric acid

D. the formation of hypochlorous acid

All of the following factors contribute to hospital-acquired infections EXCEPT A. gram-negative bacteria are often resistant to disinfectants. B. bacteria may be present in commercial products such as mouthwash. C. invasive procedures can provide a portal of entry for bacteria. D. some bacteria metabolize disinfectants. E. All of these factors may contribute to hospital-acquired infection.

E. All of these factors may contribute to hospital-acquired infection.

Which of the following best describes the pattern of microbial death? A. All the cells in a culture die at once. B. The pattern varies depending on the antimicrobial agent. C. The pattern varies depending on the species. D. Not all of the cells in a culture are killed. E. The cells in a population die at a constant rate.

E. The cells in a population die at a constant rate.

Which of the following substances is used for surgical hand scrubs? A. soap B. phenol C. chlorine bleach D. glutaraldehyde E. chlorhexidine

E. chlorhexidine

Which method below is used to preserve food by slowing the metabolic processes of foodborne microbes? A. ionizing radiation B. pasteurization C. lyophilization D. nonionizing radiation E. freezing

E. freezing

Which of the following results in lethal damage to nucleic acids? A. heat B. radiation C. certain chemicals D. heat and radiation E. heat, radiation, and some chemicals

E. heat, radiation, and some chemicals

An iodophor is a(n) A. phenol. B. quaternary ammonium compound. C. agent that reduces oxygen. D. form of formaldehyde. E. iodine mixed with a surfactant.

E. iodine mixed with a surfactant.

Which of the following is the best method to sterilize heat-labile solutions? A. autoclave B. freezing C. pasteurization D. dry heat E. membrane filtration

E. membrane filtration

Which of the following does NOT achieve sterilization? A. ethylene oxide B. dry heat C. supercritical fluids D. autoclave E. pasteurization

E. pasteurization

Any process that destroys the non-spore forming contaminants on inanimate objects is sterilization. True False

False

Desiccation is a reliable form of sterilization. True False

False

Microorganisms placed in high concentrations of salts and sugars undergo lysis. True False

False

A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In the table, which compound was bactericidal? A B C D The answer cannot be determined.

The answer cannot be determined.

Autoclaving is the most effective method of moist heat sterilization. True False

True

Moist heat destroys organisms by denaturing proteins. True False

True

Some antimicrobial chemicals are considered to be disinfectants and antiseptics. True False

True

The thermal death time is the time needed to kill all the bacteria in a particular culture at a certain temperature. True False

True