MicroBio Ch. 13 Review Questions

Which is more effective at killing microbes: autoclaving or freezing? Explain.

- Autoclaving is used to raise temperatures above the boiling point of water to sterilize items such as surgical equipment from vegetative cells, viruses, and especially endospores, which are known to survive boiling temperatures, without damaging the items. - Freezing below −2 °C may stop microbial growth and even kill susceptible organisms. However, once unthawed, bacterial growth can start again.

How does the addition of salt or sugar help preserve food?

- The water content of foods and materials, called the water activity, can be lowered without physical drying by the addition of solutes such as salts or sugars. - the amount of available water in microbial cells is reduced dramatically because water will be drawn from an area of low solute concentration (inside the cell) to an area of high solute concentration (outside the cell)

What are some factors that alter the effectiveness of a disinfectant?

- length of exposure - intensity of exposure -temperature of disinfecting agent - concentration of disinfecting agent -Conditions that limit contact between the agent and the targeted cells cells—for example, the presence of bodily fluids, tissue, organic debris, biofilms on surfaces.

What are some characteristics of microbes and infectious agents that would require handling in a BSL-3 laboratory?

- potential to cause lethal infections - from a foreign location - Ex: West nile virus, HIV

What is the advantage of using an iodophor rather than iodine or an iodine tincture?

-Iodophor is a compound of iodine complexed with an organic, making it more stable and efficient. -An iodine tincture is very in volatility, limiting effectiveness to immediately after application

Which solution of ethyl alcohol is more effective at inhibiting microbial growth: a 70% solution or a 100% solution? Why?

70% This is because alcohols coagulate proteins. In higher alcohol concentrations, rapid coagulation of surface proteins prevents effective penetration of cells.

The effectiveness of chemical disinfectants has historically been compared to that of which of the following? A. phenol B. ethyl alcohol C. bleach D. formaldehyde

A

Which of the following microbial control methods does not actually kill microbes or inhibit their growth but instead removes them physically from samples? A. filtration B. desiccation C. lyophilization D. nonionizing radiation

A

Which of the following peroxygens is widely used as a household disinfectant, is inexpensive, and breaks down into water and oxygen gas? A. hydrogen peroxide B. peracetic acid C. benzoyl peroxide D. ozone

A

Which of the following types of medical items requires sterilization? A. needles B. bed linens C. respiratory masks D. blood pressure cuffs

A

Bleach is an example of which group of chemicals used for disinfection? A. heavy metals B. halogens C. quats D. bisbiguanides

B

Which biosafety level is appropriate for research with microbes or infectious agents that pose moderate risk to laboratory workers and the community, and are typically indigenous? A. BSL-1 B. BSL-2 C. BSL-3 D. BSL-4

B

Which of the following chemical food preservatives is used in the wine industry but may cause asthmatic reactions in some individuals? A. nitrites B. sulfites C. propionic acid D. benzoic acid

B

Which of the following is suitable for use on tissues for microbial control to prevent infection? A. disinfectant B. antiseptic C. sterilant D. water

B

Which of the following refers to a disinfecting chemical dissolved in alcohol? A. iodophor B. tincture C. phenolic D. peroxygen

B

The decimal reduction time refers to the amount of time it takes to which of the following? A. reduce a microbial population by 10% B. reduce a microbial population by 0.1% C. reduce a microbial population by 90% D. completely eliminate a microbial population

C

Which chemical disinfectant works by methylating enzymes and nucleic acids and is known for being toxic and carcinogenic? A. sorbic acid B. triclosan C. formaldehyde D. hexaclorophene

C

Which of the following refers to a germicide that can kill vegetative cells and certain enveloped viruses but not endospores? A. high-level germicide B. intermediate-level germicide C. low-level germicide D. sterilant

C

Which of the following terms is used to describe the time required to kill all of the microbes within a sample at a given temperature? A. D-value B. thermal death point C. thermal death time D. decimal reduction time

C

Which type of test is used to determine whether disinfectant solutions actively used in a clinical setting are being used correctly? A. disk-diffusion assay B. phenol coefficient test C. in-use test D. use-dilution test

C

The goal of ________ ________ protocols is to rid canned produce of Clostridium botulinum endospores.

Commercial sterilization

Doorknobs and other surfaces in clinical settings are often coated with ________, ________, or ________ to prevent the transmission of microbes.

Copper, nickel, zinc

Which of the following best describes a microbial control protocol that inhibits the growth of molds and yeast? A.bacteriostatic B. fungicidal C. bactericidal D. fungistatic

D

Which of the following methods brings about cell lysis due to cavitation induced by rapid localized pressure changes? A. microwaving B. gamma irradiation C. ultraviolet radiation D. sonication

D

What is the purpose of degerming? Does it completely eliminate microbes?

Ex - handwashing, alcohol swab - remove most but not all germs. - microbial numbers are significantly reduced by scrubbing living tissue, most commonly skin, with a mild chemical to avoid the transmission of pathogenic microbes.

T/F Moist-heat sterilization protocols require the use of higher temperatures for longer periods of time than do dry-heat sterilization protocols do.

F

T/F Sanitization leaves an object free of microbes.

F

T/F Soaps are classified as disinfectants.

F

If a chemical disinfectant is more effective than phenol, then its phenol coefficient would be ________ than 1.0.

Greater

If used for extended periods of time, ________ germicides may lead to sterility.

High-Level

Why were chemical disinfectants once commonly compared with phenol?

It was a disinfectant for the treatment of surgical wounds.

Why is length of exposure to a chemical disinfectant important for its activity?

Length of exposure is important to kill as many microbes as possible. The longer the time frame, the more you kill

A medical item that comes into contact with intact skin and does not penetrate sterile tissues or come into contact with mucous membranes is called a(n) ________ item.

Noncritical

In an autoclave, the application of pressure to ________ is increased to allow the steam to achieve temperatures above the boiling point of water.

Steam

What is the advantage of HTST pasteurization compared with sterilization? What is an advantage of UHT treatment?

Sterilization will alter the quality of the product. HTST pasteurization(high temp short-time) - lowers bacterial numbers while preserving the quality of the product. (milk) UHT treatment (ultra-high temp) - can be stored for a long time in sealed containers without being refrigerated - however, the very high temperatures alter the proteins in the milk, causing slight changes in the taste and smell

In the disk-diffusion assay, a large zone of inhibition around a disk to which a chemical disinfectant has been applied indicates ________ of the test microbe to the chemical disinfectant.

Susceptibility or sensitivity

T/F Ionizing radiation can penetrate surfaces, but nonionizing radiation cannot.

T

T/F Mercury-based compounds have fallen out of favor for use as preservatives and antiseptics.

T