Microbiology HW Ch. 7

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Dr. Eccles assigned Mastering Microbiology Homework

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:

Antisepsis; is the destruction of vegetative pathogens on living tissue.

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:
-toxins produced by the microbe
-the time of exposure
- the number of microbes
- the microbial characteristics

Toxins; Although microbial toxins may influence the status of an infection, these factors do not influence the death rate of the organism.

Microbial control methods usually target any of the following microbial structures EXCEPT:
-nucleic acids
- mitochondria
- microbial proteins
- plasma membrane permeability

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.

Which of the following physical methods of microbial control denatures proteins as a mechanism of action?
-boiling or autoclaving
- incineration
- osmotic pressure
- radiation

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

Gluteraldehydes are among the most effective chemical control agents because they:

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.

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?

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.

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?

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.

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:
-halogens
- acid-anionic sanitizers
- soaps and detergents
- quaternary ammonium compounds (quats)

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.

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?
- iodine
- phenolics
- alcohols
- chlorines

Chlorine has the best overall action against both of these targets

Correctly list, in increasing order, the resistance of microorganisms to chemical biocides:

gram-positive bacteria, fungi, endospores, prions

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