Chapter 9

It has been determined that the temperature in an autoclave should reach __________ for sterilization.

121 degrees Celsius

Which of the following best explains why the pressure cooker is so important in the canning process?

A pressure cooker utilizes steam to create a higher-pressure environment that allows the food to cook at higher temperatures than normal. The higher temperatures kill most contaminating microbes and endospores and therefore effectively sterilize the food.

Which biosafety level requires that laboratory air be HEPA-filtered but is insufficient for the safe study of Ebola?

BSL-3

Why is autoclaving rather than boiling water used for sterilization?

Boiling water does not kill everything, including bacterial endospores and some protozoan cysts.

During production of a drug, all work area surfaces must be disinfected using sterilized disinfectants. Which of the following statements about disinfectants are true?

Disinfection can occur by physical or chemical means. Endospores and viruses can resist disinfectant treatment. Disinfectants are used to inhibit or destroy pathogens. Submit

Why are endospores used to measure the effectiveness of autoclave sterilization?

Endospores are very hard to kill.

Use of moist heat can control microbial growth in many circumstances, but heat-sensitive items and those susceptible to moisture cannot be sterilized in this manner. Which of the following correctly describes a method of physical control used to control microbial growth on or in such items?

Filtration is the passage of a liquid or a gas through a screenlike material with pores small enough to retain microorganisms. A vacuum is typically used to force the liquid through the mesh, and then the sterile liquid or gas is collected in a sterile container on the other side. Nonionizing radiation, such as UV light, has a wavelength longer than that of ionizing radiation. The wavelengths of UV light are absorbed by cellular DNA in organisms directly exposed to the light. Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable. Osmotic pressure is a process that uses high concentrations of salts and sugars to preserve food.

Which of the following is an example of pasteurization?

Heat is used to kill potential pathogens in apple juice.

Why do containers of liquid placed in an autoclave need to remain at least slightly open?

If they remain closed, they may implode.

Which of the following is NOT a desirable characteristic of an ideal antimicrobial agent?

It only arrests growth of vegetative cells.

Botulism food poisoning is a preventable illness if special precautions are taken during food preparation. In this case, what could Sue have done to prevent the outbreak of botulism?

Sue noticed that the pressure cooker was malfunctioning during the canning process. She should have fixed the instrument, borrowed a properly working one, or purchased a new pressure cooker.Sue could have boiled the food for at least 10 minutes before serving it to her family members.

Mary loved having her own garden and would often spend many hours tending to its care. She was meticulous in watering the plants, pulling the dreaded weeds, and harvesting the fruits and vegetables as they ripened. Her garden consisted of corn, tomatoes, green beans, okra, zucchini, squash, lima beans, watermelon, and cantaloupe. Often, the garden would produce much more than Mary and her daughter, Sue, could eat. Rather than waste the delicious food, the ladies would spend hours on the weekend canning the excess vegetables and fruit. It was something they had done for many years. On this particular occasion, Sue noticed that the pressure cooker, the instrument used to sterilize the canned food, did not seem to be acting quite right, but the cans were hot when they came out so she figured everything would be okay.Several months after their weekend of canning, the ladies invited the entire family over for Thanksgiving dinner. The meal consisted of turkey, ham, chicken, macaroni and cheese, rolls, spinach salad, tomatoes, corn, lima beans, green beans, and okra. All of the vegetables were the ones they had previously canned from their garden. For dessert, they had pecan pie and vanilla ice

Sue washes off the vegetables before serving them in a meal. Sue uses bleach to clean the kitchen counters. Mary places leftovers in the refrigerator after the meal.

Sodium nitrate and sodium nitrite are added to many meat products, such as ham, bacon, hot dogs, and sausage. These additives help to prevent the growth of Clostridium botulinum by inhibiting certain iron-containing enzymes of the organism. This is an example of chemical food preservation. Which of the following correctly describes a method of chemical control used to control microbial growth?

Surface-active agents, or surfactants, decrease surface tension among molecules of a liquid. Phenolics exert antimicrobial activity by injuring lipid-containing plasma membranes, which causes the cellular components to leak out of the cell. Alcohols exert their action by denaturing proteins and dissolving lipids.

The preferred method of sterilization during drug production is heat. Heat sterilization can occur in two forms: moist or dry. Autoclaving is the most commonly used application of moist heat for sterilization. Which of the following statements about autoclaving is true? Autoclaving is preferred over dry heat because it can effectively be used to sterilize a wide variety of items, including liquids, powders, metal instruments, and glassware. When autoclaving solid items, they should be wrapped in foil to help maintain sterility. Autoclaving requires extensive exposure times in order to achieve sterilization .The effectiveness of an autoclave is dependent on an increase in pressure and corresponding increase in temperature.

The effectiveness of an autoclave is dependent on an increase in pressure and corresponding increase in temperature. Submit

What was the MOST likely source of the family's botulism food poisoning?

The family consumed botulism toxin in the canned green beans. (The canned green beans are the most likely culprit for botulism toxin. C. botulinum is a soil microbe that could be found on green beans. If the canned beans were not prepared and canned properly, then the organism would be able to survive. It is less likely that C. botulinum could survive in the canned tomatoes, because tomatoes are very acidic. The family ingested the toxin with the green beans, and that is why they suffered from botulism food poisoning.)

Why are endospores sometimes used in sterility indicators?

They are the hardest life form to kill.

How do scientists ensure that autoclaved materials were actually sterilized?

They may place a sterility indicator with a special dye to detect the growth of endospores.

What role does pressure play in an autoclave?

What role does pressure play in an autoclave?

An antimicrobial chemical used on the skin is called __________.

an antiseptic

The use of lysozyme during the preparation of cheeses and wines is effective in reducing the numbers of

bacteria

One alternative to autoclaving for sterilization of liquids is filtration. Imagine that you are using a filter to sterilize a drug solution. You use a filter with a 0.22 pore size. Which of the following microbes will effectively be removed by this filter?

bacteria, yeast, fungi

Which of the following is the most difficult to inactivate?

bacterial endospores

Disinfectants that damage membranes include

both alcohol and phenolics.

Hydrogen peroxide does NOT make a good antiseptic for open wounds because __________.

catalase in human tissues neutralizes it

A chemical agent that dissolves lipids can damage

cells and enveloped viruses.

A nurse rubbing a section of skin with an alcohol pad prior to an injection is an example of _____.

degerming

Washing dishes in the dishwasher with detergent and hot water is a ________ process.

degerming and disinfecting

viruses are susceptible to

envelope protein attacks

Quaternary ammonium compounds are disinfectants effective against

enveloped viruses.

NASA wants to prevent the possibility of contaminating other planets or items in space with microbes from Earth. Which of the following would best be used to sterilize spacecraft being sent to space?

ethylene oxide

Which of the following is used to sterilize items that should not, or cannot, be exposed to heat or water?

ethylene oxide

The cell walls of mycobacteria make them vulnerable to water soluble chemical agents.

false

A scientist develops a new medication that is a protein compound and that must be administered by injection. Which of the following would be the most effective and safest means of preparing a sterile solution of the new medication?

filtration

Aseptic means

free of pathogens.

Which of the following is bacteriostatic?

freezing below 0°C

A chemical agent that kills pathogenic microbes in general is a(n)

germicide.

Betadine contains what type of chemical agent?

halogen

Desiccation, a time-honored method of preserving food, is effective because the

heat of the process kills microbes.

An instrument coming into contact with the skin of an immunocompromised patient should be treated with which of the following?

high-level germicide

Where are you likely to find an autoclave?

in a dentists office

If you wanted to evaluate a new disinfectant for effectiveness under the conditions of its intended use, the best evaluation technique would be the __________ test.

in-use

Apply your knowledge of the structural features of microbes and the mechanisms of action for antimicrobial agents to rank the following microbes according to their susceptibility.

least:prions, endospores, gram-negatives, gram=positives, enveloped virus:Most (Microbial structure plays an important role in susceptibility to antimicrobials. While you might think that a viral envelope would confer protection, it is more easily broken down than a protein coat. Gram-positive bacteria tend to be more susceptible to agents that attack the cell wall (recall that they lack an outer membrane). Bacterial endospores are designed to withstand extreme stress; this also means that they are more difficult to eliminate compared to bacterial cells. Prions remain the most resistant of all; however, recently, an enzyme has been shown to be effective in eliminating prion contamination on medical instruments.)

all bacteria are susceptible to attacks on

membrane proteins and glycolytic enzymes

Which of the following is the most appropriate pairing of microbe and biosafety level?

methicillin-resistant Staphylococcus aureus (MRSA), BSL-2 Submit

You notice a sign in a public restroom that states "Sanitized for your safety." This means

methods of disinfection that meet minimum standards of microbial removal have been used.

all bacteria and viruses are susceptible to

nucleic acid attacks

gram-positive are susceptible to

peptidoglycan attacks

Which of the following is a sterilizing agent?

peracetic acid and hydrogen peroxide

Antimicrobial agents that damage nucleic acids also affect

protein synthesis.

Ultra-high-temperature sterilization effectively

removes all microbes that cause diseases or spoilage.

The process of incineration is used for

sterilization.

What is the purpose of an autoclave?

to sterilize equipment and media (kills bacteria, viruses, fungi and spores)

Which of the following achieves sterilization in the shortest period of time?

ultra-high-temperature sterilization

Which of the following types of radiation is non-ionizing and has the shortest wavelength?

ultraviolet light

Which of the following procedures is currently the standard test used in the United States for evaluating the efficiency of antiseptics and disinfectants?

use-dilution test

Which of the following is NOT a feature associated with filtration?

varying thicknesses of membrane filters used