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Unformatted text preview: luencing Effectiveness of Antimicrobial Treatments
7. Presence of organic matter Chemicals adsorb to organic matter, blocking action on microbes May require cleaning of materials (i.e. surgical instruments) before disinfection Death Values Death Values “D value” = time it takes to kill 90% of bacterial population under specific conditions Indicates how much time is needed to sterilize an area depending on the level of contamination Example: If the D value for an organism is 3 minutes, it would take how long to reduce a population of 10,000 cells down to 1 cell? 3 minutes after initial application 1000 cells remain After 3 more minutes 100 cells remain After 3 more minutes 10 cells remain After 3 more minutes 1 cell remains Final answer: 12 minutes Physical Methods: Heat Physical Methods: Heat
Moist heat (boiling) Dry heat (baking) Steam heat (autoclave) Limits Uses Effective against: vegetative Drinking water bacteria, fungi, and viruses; endospores are not affected Effective against: all microbes Very slow (4 hrs), high heat Effective against: all microbes Glassware, large metal objects Canned foods, media, surgical instruments Milk, juices, egg products Pasteurization Effective against: some bacteria and fungi Quick, high heat Physical Methods Heat Physical Methods Heat Steam heat: Pressure cookers, autoclaves heat water in...
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- Fall '09