ATQ- Sterilization and Aseptic Technique

Mariela Cassandra L. Mendoza MBB 110: Exercise 1 STERILIZATION AND THE ASEPTIC TECHNIQUE 1. Define sterilization, disinfection, and decontamination. What are their differences and when are they performed? Sterilization is a set of procedures done to eliminate all forms of life, mainly microorganisms from any material particularly glassware, equipment and solutions to be used in the laboratory. Heat, ethylene oxide gas, hydrogen peroxide gas, plasma, ozone and radiation are used in sterilization procedures. The sterility assurance level is attained if the probability of a microorganism surviving on an item subjected to the procedure is less than one in one million (Chosewood & Wilson, 2009). Disinfection is a process wherein all recognized pathogenic microorganisms are eliminated from an item. Unlike sterilization, disinfection does not necessarily eliminate all forms of microbial life (e.g. bacterial spores) (Chosewood & Wilson, 2009). The effectiveness of a disinfection procedure is dependent on factors such as the nature and number of contaminating microorganisms (especially the presence of bacterial spores), amount of organic matter present (e.g., soil, feces and blood), type and condition of materials to be disinfected and the temperature. Chosewood and Wilson (2009) also stated that disinfection procedures are classified into three levels in terms of the effectiveness of the procedure in reducing the level of microbial contamination in an object: High-level disinfection process eliminates vegetative microorganisms and inactivates viruses. This process can also kill bacterial spores but disinfectants used would require a long period of time (e.g., 6 to 10 hours) to create sterilization. Such disinfectants are generally used on medical devices but not on surfaces such as floors and benches. A much more similar process to this is Intermediate-level disinfection except in the sense that the process is not capable of sterilization even when disinfectants are applied for long period of time. This process is more commonly used in the laboratory and for housekeeping purposes. Lastly, Low-level disinfection process inactivates some viruses and kills most vegetative bacteria except M. tuberculosis. Disinfectants of this level are generally used as hospital disinfectants or sanitizers. Decontamination is the use of sterilization and disinfection techniques to free a person, object or an area from potentially harmful microorganisms and render it safe for use (Block, 2001). In the microbiology laboratory, decontamination aims to protect the laboratory worker, the environment or anybody who had physical contact to the laboratory and its equipment (Chosewood & Wilson, 2009).. 2. There are types of solutions or reagents that cannot be heated but instead filtered to make them devoid of contaminants. Give examples of these types of solutions. Solutions that can’t be autoclaved but can be filtered are mostly heat sensitive liquids such as serum, antibiotic solutions, sugar solutions and urea solutions (Rao, 2008). Aside from this, special

culture media that are also prone to heat damage are also decontaminated through filtration which can successfully isolate microbes but not mycoplasmas and viruses (Collins, Lyne, & Grange, 1995).

3. What are biosafety cabinets? How do they differ from laminar flow hoods? When are they used? Biosafety cabinets (BSC) are entirely enclosed environments that are available in positive or negative airflow (Elsevier Health Sciences, 2014). These are also known as glove boxes or isolator hoods which differ from laminar flow hoods (LFH) in a sense that BSCs are applicable for both infectious and non-infectious work whereas LFHs are only used for non-infectious work. In particular, (University of Massachusetts Amherst, 2015) stated that BSCs are used when working with potentially infectious and pathogenic microorganisms, as well as cell cultures and drug formulations which should never be performed inside a laminar flow hood. While open face LFHs only protect the product inside the hood, BSCs protect both the user and the items inside the cabinet as it has a sash in front. Lastly, air in LFHs are blown towards the user while air in BSCs are drawn away from the uses.

4. What are the modes of action of alcohol and Lysol? What other reagents maybe used to disinfect surfaces? According to Harisha (2006), Lysol’s active agent is orthophenylphenol, a phenolic compound which has germicidal properties due to its ability to alter membrane permeability and protein structure which can result to denaturation. Similar to Lysol, alcohols (either ethyl or isopropyl) also cause denaturation of proteins as stated by Cappuccino & Sherman (2007). It also works as a lipid solvent and a wetting agent (in tinctures) to increase wetting ability of other reagents Aside from lysol and alcohol, other reagents that are used as disinfectants are chemicals like formaldehyde, ethylene oxide, and halogens namely sodium hypochlorite and chloramine.

REFERENCES [1] Chosewood, L. C & Wilson, D.E. (2009). Biosafety in Microbiological and Biomedical Laboratories (5th ed). USA: Centers for Disease Control and Prevention, National Institutes of Health [2] Block, S.S. (2001). Disinfection, Sterilization and Preservation. Philadelphia: Lippincott Williams and Wilkins [3] Rao, S. (2008, June). Sterilization and Disinfection. Retrieved January 30, 2015, from http://www.microrao.com/micronotes/sterilization.pdf [4] Collins, C., Lyne, P. & Grange, J. (1995) Collins and Lyne's microbiological methods (7th ed.) London: Butterworth-Heinemann.

[5a] Elsevier Health Sciences (2014). Mosby's Pharmacy Technician: Principles and Practice (4th ed). Canada: Elsevier, Inc. [5b] University of Massachusetts Amherst. (2015). Environmental Health & Safety Fact Sheet: Biological Safety Cabinets vs. Laminar Flow Hoods. Retrieved January 30, 2015, from https://www.ehs.umass.edu/sites/default/files/Fact-Sheet-BSC-vs-LFH.pdf [6] Harisha, S. (2006). An Introduction to Practical Biotechnology (1st ed). New Delhi: Laxmi Publications Ltd. [7] Cappuccino, J., & Sherman, N. (2007). Microbiology: A Laboratory manual (8th ed). San Francisco: Benjamin Cummings Publishing Company