MIC201 Lectures Part III

MIC201 Lectures Part III - PHYSICAL METHODS FOR PHYSICAL...

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Unformatted text preview: PHYSICAL METHODS FOR PHYSICAL METHODS FOR CONTROLLING MICROORGANISMS CONTROLLING MICROORGANISMS I. Heat - I. Heat - Thermal Death Time Thermal Death Time (time at which organism (time at which organism is killed at a given temperature) time and temperature is killed at a given temperature) time and temperature related death related death A. Direct Flame seconds A. Direct Flame seconds B. Hot Air - 160C for 2 hours (oxidizes protein) - good B. Hot Air - 160C for 2 hours (oxidizes protein) - good for: powders, oily substances, and glassware [dry for: powders, oily substances, and glassware [dry heat does not penetrate well] heat does not penetrate well] C. Boiling Water - spores may take several hours to kill C. Boiling Water - spores may take several hours to kill ( ( C. botulinum C. botulinum >24 h) (denaturing protein) >24 h) (denaturing protein) D. Autoclave - 121C (15 psi) live steam, no air - good D. Autoclave - 121C (15 psi) live steam, no air - good for: blankets, bedding, utensils, intravenous solutions, for: blankets, bedding, utensils, intravenous solutions, and lab media [moist heat] and lab media [moist heat] II. Filtration A. Seitz - (asbestos) porcelain - not really used any more! B. Diatomaceous Earth - as a filtering aid, to clarify solutions C. Membrane Filters - (cellulose acetate and mixed esters) - used for detecting contamination and sterilization of solutions that are heat labile III. UV-light - (265nm wavelength) produces Thymine dimers in the cell's DNA used mostly to keep air and surface contamination down [UV-light has very weak penetration power] IV. Ionizing Radiation - (X-rays and -rays) these create organoperoxides and other ions that break DNA [microwaves?] V. Cavitation - (ultra-sonication) - used in cleaning instruments and breaking open microorganisms [does so by creating many tiny vacuums] CHEMICAL METHODS OF CHEMICAL METHODS OF CONTROLLING MICROORGANISMS CONTROLLING MICROORGANISMS Disinfectant Disinfectant versus versus Antiseptic Antiseptic Bactericidal Bactericidal versus versus Bacteriostatic Bacteriostatic Qualities: fast-acting, broad-spectrum, long shelf life, non- Qualities: fast-acting, broad-spectrum, long shelf life, non- toxic to humans, water soluble, good penetrating power toxic to humans, water soluble, good penetrating power and not very reactive with organic debris [functional and not very reactive with organic debris [functional...
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MIC201 Lectures Part III - PHYSICAL METHODS FOR PHYSICAL...

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