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Methods to sterlize instruments

How would the following items best be sterilized: a wrapped package of Petri dishes, antibiotic solution, agar media, glass pipettes and individual Petri dishes.

ii) What are the advantages and disadvantages of U.V. light and ionizing radiation as sterilizing agents?

iii) Compare and contrast dry heat and moist heat as methods of microbial control.

iv) Define the following chemical substances in their action against microbes: sanitizer, germicide, antiseptic, disinfectant

v) Describe each of the following in terms of its chemical nature, mechanism of action, mode of application, common uses and effectiveness, and advantages and disadvantages: heavy metals, phenolics, halogens

vi) Describe the mechanism of action for the following families of antibiotics: cephalosporins, sulfa drugs, aminoglycodsides

Solution Preview

How would the following items best be sterilized:

a wrapped package of Petri dishes - ionizing radiation for plastic Petri dishes, moist heat for glass Petri dishes
antibiotic solution - filter sterilization (0.2 micron filter)
agar media - moist heat
glass pipettes - moist or dry heat
individual Petri dishes. - UV irradiation

ii) What are the advantages and disadvantages of U.V. light and ionizing radiation as sterilizing agents?

UV light is safe, cheap and convenient to use, and appropriate for surface sterilization and for some transparent objects. However it does not penetrate into liquids, shaded areas or opaque objects, which limits widespread usefulness. Ionizing radiation such as X-rays and gamma radiation is very penetrative and can be used to sterilize medical equipment and large or stacked items. A disadvantage is that it requires large specialized equipment (X-rays) or a radioactive isotope source (gamma radiation), which are expensive and pose potential health risks to the operator.

iii) Compare and contrast dry heat and moist heat as methods of microbial control.

The temperature used for sterilization is higher when using dry heat, approximately 160 degrees C for 60 minutes, so it is only suitable for items not damaged by heat such as ...

Solution Summary

This solutions addresses several questions regarding the use of specific methodologies to sterilize instruments. It details the methods by which the various methods work, provides comparisons between the different methods and also the mechanisms of action of certain antibiotics.

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