Ya Allah Flashcards
What’s a bio burden
is an estimate of total viable count of M.Os present pre-sterilization
What are the methods to reduce the number of MO
– Sterilization
– Disinfection
– Antiseptic
What is sterilisation
The process of destroying all forms of microbial life on an object or in a material. This includes the destruction of
endospores
IT IS ABSOLUTE
What are the typical temperatures for sterilisation
Moist heat at 121 for 15mins
Dry heat 170 for 120 mins
What does disinfection means
The process of destroying vegetative pathogens, but not necessarily endospores or viruses
It’s not usually sterilize
Disinfectant= non-living objects
What’s an antiseptic
Chemical disinfections of the skin, mucous membranes, or other living tissues. This term is especially applied to treatment of wounds.
Antiseptic= living
What is commercial sterilisation
is heat treatment of canned foods to destroy the
endospores of Clostredium botulinum
What does degerming means
is removal of microbes from limited
area
What are the factors that effect antimicrobial activity
- Temp
- Time
- Concentration of Antimicrobial agent
- Type of Microbe
- Activity of Microbe
- Presence of organic matter
- Microbial inoculum
- Microbial Phenotype (planktonic vs biofilm)
What are the physical methods of sterilisation
1.heat(moist and dry)
2. Filtration
3. Desiccation
4. osmotic pressure
5. Radiation
• Ionizing Radiation
• Non-Ionizing Radiation
What are the moist heat methods
Boiling Water
• Steam Heat (Autoclave)
• Pasteurization (Heat)
• Tyndallization
What are the dry heat methods
- Direct Flaming
- Incineration
- Hot Air Sterilization (Oven)
How does heat sterilisation work
❖works by denaturing enzymes and proteins
What are the following
TDP
TDT
DRT(D VALUE)
A. Thermal Death Point (TDP)
– lowest temp. at which all microorganism in a liquid culture are killed in 10 minutes
B. Thermal Death Time (TDT)
– minimum length of time in which all microorganisms in a liquid culture are killed at a given temperature
C. Decimal reduction time (DRT, or D value: survival curve)
– time needed to kill 90% of living microbes
The higher the D value the more resistant the bacteria
True
How does boiling work
Kills microorganisms by irreversibly coagulatingn their proteins.
What does boiling kill
vegetative forms of bacterial pathogens,
–many viruses, and fungi and their spores within about 10 minutes.
not effective for endospores and some viruses
– Hepatitis (20 min)
– Some spores may survive boiling water for up to 20 hrs
How can we reach higher temperatures
by steam under pressure in an autoclave
The higher the pressure the higher the temperature
What’s the time and pressure in an autoclave at 121
15 psi
15mins
What’s flash autoclaving
Flash autoclaving sterilizes at 135°C and 35psi in 3 minutes
What is classic pasteurization
milk was exposed to a temperature of about 63oC for 30 minutes
What is HTST
Milk treatmentat least 72o C, but for only about 15 seconds
How do we determine of a product is pasteurised
Phosphatase test (enzyme in the milk)
If the product pasteurized this enzyme will be
inactivated
What is UHT pasteurization
The milk falls in a thin film through a chamber of superheated steam reach 140 C in less than secondnand hold for 4 seconds then cooled in a vacuum chamber
- Within 5 seconds;
- 74 °C ———–140 C ————-74 C
