Needles Disinfection
about sterilization and disinfection?
1. What is the hazard of the splattering tendency in sterilizing a wire loop over a flame?
2. Can wire loops and needles be sterilized by autoclaving?
3. Under what conditions is sterilization by filtration preffered over sterilization by heat?
4. Can culture media be sterilized in the hot air sterilizer? why or why not?
5. Why is heat an effective sterilizing agent?
6. Why is time of exposure and temperature required for sterilization greater for dry heat(160-180 C for 1-2 h0 than for autoclaving(121 C for 15 mins)?
7. What is the meaning of minimum inhibitory concentration?
1. Loops can hold moisture in small droplets. Placing them directly in the flame while wet can cause the moisture to turn to steam and spatter hot liquid onto unprotected face/skin.
2. Yes
3. When the liquid you need sterilized contains something that is heat labile (meaning it breaks down if it gets too hot), you would need to filter it, as opposed to heating it.
4. Hot air sterilizers would cause liquid media to boil and evaporate, destroying all of your hard work!
5. Heat denatures the proteins of contaminating microbes. Without those proteins, microbes cannot maintain structure or run biochemical reactions.
6. Many microbes have forms that are heat-stabile and can actually come back to life after being dried out. Autoclaving uses a lot of pressure along with heat to break through that protection and kill the cells once and for all.
7. The lowest concentration of a substance (e.g. bleach) needed to prevent the growth of a microorganism. This depends both on the organism as well as the type of antibacterial substance.
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