Chapter 7 The Control of Microbial Growth Flashcards
refers to bacterial contamination
النسيج الذي تتم دراسته مصاب بالبكتيريا او متلوث فيها
والعكس لما تكون المنطقة معقمة وخالية من البكتيريا ؟؟
Sepsis
Asepsis
removing and destroying all microbial life
Sterilization
killing Clostridium botulinum endospores from canned goods
Commercial sterilization
destroying harmful microorganisms
•destroying harmful microorganisms from living tissue
Disinfection: destroying harmful microorganisms
• Antisepsis: destroying harmful microorganisms from living tissue
the mechanical removal of microbes from a limited area
Degerming
lowering microbial counts on eating utensils to safe levels
Sanitization
treatments that kill microbes
• inhibiting, not killing, microbes
Biocide (germicide): treatments that kill microbes
• Bacteriostasis: inhibiting, not killing, microbes
The Rate of Microbial Death
• Effectiveness of treatment depends on:
(4)
– Number of microbes
– Environment (organic matter, temperature, biofilms)
– Time of exposure
– Microbial characteristics
Actions of Microbial Control Agents (3)
- Alteration of membrane permeability • Damage to proteins (enzymes)
- Damage to nucleic acids
lowest temperature at which all cells in a liquid culture are killed in 10 min
Thermal death point (TDP):
minimal time for all bacteria in a liquid culture to be killed at a particular temperature
Thermal death time (TDT):
– Minutes to kill 90% of a specific population of
bacteria at a given temperature
Decimal reduction time (DRT)
Moist heat coagulates/denatures proteins → • Includes:
Boiling
Free-flowing steam
Autoclave:
steam under pressure
• 121°-C at 15 psi (pounds of pressure per square Inch) for 15 min
• Kills all organisms and endospores
• Steam must contact the item’s surface
