Microbiology Chapter 13
What are some characteristics of microbes and infectious agents that would require handling in a BSL-3 laboratory?
-Contaminated air requiring constant supple of clean air, pathogenic/possibly need vaccination for microbe they are working with, air/blood born, special gear/training, use under hood
What are some factors that alter the effectiveness of a disinfectant?
-length of exposure, concentration, temperature, pH
Why is length of exposure to a chemical disinfectant important for its activity?
-longer exposure means increasing efficacy of chemical disinfectant
Which solution of ethyl alcohol is more effective at inhibiting microbial growth: a 70% solution or a 100% solution? Why?
70%; gains trust then takes em out at the knees (in higher alcohol concentrations, rapid coagulation of surface proteins prevents effective penetration of cells) - 70% alcohol in aqueous solution works best
Which is more effective at killing microbes: autoclaving or freezing? Explain.
Autoclaving; it's the most effective method of sterilization allowing moist heat on large scale without damaging items Freezing just stops growth of microbes
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? BSL-1 BSL-2 BSL-3 BSL-4
BSL-2
When plotting microbial death curves, how might they look different for bactericidal versus bacteriostatic treatments?
Bactericidal: kills completely Bacteriostatic: stops growth without killing
What are the benefits of cleaning something to a level of cleanliness beyond what is required? What are some possible disadvantages of doing so?
Benefits: maintaining health Disadvantages: killing all microbes is bad, they can build resistance, stripping all microbes can result in death
What is the advantage of HTST pasteurization compared with sterilization? What is an advantage of UHT treatment?
HTST advantage: lowers bacterial numbers while preserving the quality of the milk UHT advantage: can be stored for long time in sealed containers without refrigerated (regions in which access to refrigeration is limited)
Why were chemical disinfectants once commonly compared with phenol?
Historically they often compared disinfectants with phenol because phenol was the first chemical agent used
What is the advantage of using an iodophor rather than iodine or an iodine tincture?
Iodophor: compound of Iodine complexed with an organic molecule which increases iodine's stability and in turn it's efficacy
Why is the use of skin disinfecting compounds required for surgical scrubbing and not for everyday handwashing?
It is more persistent than iodophors, providing long lasting antimicrobial activity and acts faster -Over using daily would damage and build resistance
What is the purpose of degerming? Does it completely eliminate microbes?
Microbial numbers are significantly reduced by gently scrubbing living tissue with mild chemical to avoid transmission of pathogenic microbes(ex washing hands, alcohol swab on injection site) it removes MOST( but not all) microbes from surface
In 2001, endospores of Bacillus anthracis, the causative agent of anthrax, were sent to government officials and news agencies via the mail. In response, the US Postal Service began to irradiate mail with UV light. Was this an effective strategy? Why or why not?
Yes; UV light can be used to sterilize; cells must be exposed directly to the light source because UV light doesn't penetrate surfaces unless direct contact
Which of the following is suitable for use on tissues for microbial control to prevent infection? disinfectant antiseptic sterilant water
antiseptic
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
Moist-heat sterilization protocols require the use of higher temperatures for longer periods of time than do dry-heat sterilization protocols do.
false
Sanitization leaves an object free of microbes.
false
Soaps are classified as disinfectants.
false
Which of the following microbial control methods does not actually kill microbes or inhibit their growth but instead removes them physically from samples? filtration desiccation lyophilization nonionizing radiation
filtration
Which chemical disinfectant works by methylating enzymes and nucleic acids and is known for being toxic and carcinogenic? sorbic acid triclosan formaldehyde hexaclorophene
formaldehyde
Which of the following best describes a microbial control protocol that inhibits the growth of molds and yeast? bacteriostatic fungicidal bactericidal fungistatic
fungistatic
If a chemical disinfectant is more effective than phenol, then its phenol coefficient would be ________ than 1.0.
greater
Bleach is an example of which group of chemicals used for disinfection? heavy metals halogens quats bisbiguanides
halogens
If used for extended periods of time, ________ germicides may lead to sterility.
high-level
Which of the following peroxygens is widely used as a household disinfectant, is inexpensive, and breaks down into water and oxygen gas? hydrogen peroxide peracetic acid benzoyl peroxide ozone
hydrogen peroxide
Which type of test is used to determine whether disinfectant solutions actively used in a clinical setting are being used correctly? disk-diffusion assay phenol coefficient test in-use test use-dilution test
in-use test
Which of the following refers to a germicide that can kill vegetative cells and certain enveloped viruses but not endospores? high-level germicide intermediate-level germicide low-level germicide sterilant
low-level germicide
Which of the following types of medical items requires sterilization? needles bed linens respiratory masks blood pressure cuffs
needles
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
The effectiveness of chemical disinfectants has historically been compared to that of which of the following? phenol ethyl alcohol bleach formaldehyde
phenol
The decimal reduction time refers to the amount of time it takes to which of the following? reduce a microbial population by 10% reduce a microbial population by 0.1% reduce a microbial population by 90% completely eliminate a microbial population
reduce a microbial population by 90%
Which of the following methods brings about cell lysis due to cavitation induced by rapid localized pressure changes? microwaving gamma irradiation ultraviolet radiation sonication
sonication
In an autoclave, the application of pressure to ________ is increased to allow the steam to achieve temperatures above the boiling point of water.
steam
Which of the following chemical food preservatives is used in the wine industry but may cause asthmatic reactions in some individuals? nitrites sulfites propionic acid benzoic acid
sulfites
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
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? D-value thermal death point thermal death time decimal reduction time
thermal death time
Which of the following refers to a disinfecting chemical dissolved in alcohol? iodophor tincture phenolic peroxygen
tincture
Ionizing radiation can penetrate surfaces, but nonionizing radiation cannot.
true
Mercury-based compounds have fallen out of favor for use as preservatives and antiseptics.
true
How does the addition of salt or sugar help preserve food?
Very high concentrations of sugar or salt cause the available amount of water in microbial cells to reduce dramatically because water is drawn from low solute concentration (inside cell) to areas of high solute concentration (outside cell)
