Sterilisation and disinfection Flashcards
What is sterilisation
Distructioon of all forms of life including spores
Disinfection
Destruction of only pathogenic microorganisms
Antisepsis
Distruction of living tissues
Order of susceptibility
Prions< bacterial spores < protoazoa cysts< mycobacterium < noneveloped viruses. < Fungi.
What are the physical methods of sterilisation and what is the most effective method
Heat most effective
Radiation
Filtration
Disinfectantion of mouth of test tubes ,cover slips ,slides
Dry heat flaming
Dry heat red heat used in
Sterilisation of inoculating loops, straight wires, tips of foreceps and tip of spatulas
What is incineration
Streilization and reduction in the volume of infections hospital waste before disposal
Animal car cases
Human placenta
Soiled bedding and dressings
Cytotoxic drugs
How many cambers are there in incinerator
Primary and secondary
Primary 650-750
Secondly 1050 -1100
Hot air oven
Sterilisation of metallic instruments Glassware, powders, petroleum products and sharp instruments,jellies,oils cotton swabs
No rubber products
Temperatures of hot air oven
1602 hrs
1701 hrs
180*30 min
How can we test the efficacy of hot air oven
Biological method= by spores of bacillus atrophaeus clostridium tetanus
Physical method= temperature chart recorder
Chemical method=brown tube no3
What is the mechanism of dry heat
Denaturation of proteins
Oxidative damage
Electrolytic levels of toxic levels
Mechanism of moist heat
Denaturation and coagulation of proteins
It is superior to the moist heat
Moist heat temperature
Less than 100 * c
What is pasteurisation
Disinfection of milk
Holder method= moist heat at 63*c for 30 min
Flash method= moist heat 72 c for 15 to 20 sec
Den decreases to 13 c
It is called rapid cooling
Ultra high heat method 149*c for 0.5 sec
Which organism can survive the pasteurisation
Coxiella Burnett’s can survive the holder method
Efficacy of pasteurisation
Coliform test
Pasteurised milk+ Macconkey broth
Overnight
If the process success no acid + gas
What is the phosphatase test
Pasteurisation + substrate ( disodium phenyl po4)
After 2 hrs
No colour change
What is inspissation
Moist 80-85*c fr 30 min for consecutive days
Sterilisation of egg and serum medium
Eg= loefflers medium,Ljmedium
What is Tyndallisation
At 100 *c for20 min for 3 consecutive days
What do u know about radiation
Radiation is of two types Ionising ( uv rays) non ionising ( gamma rays)
Ionising radiation eg and mechanism
Uv rays 220-240nm Mechanism = DNA damage Poor penetration Non sporicidal Disinfection of safety cabinets, hospital corridors
Ionising description
Gamma rays Mechanism DNA damage High penetration power Sporocidal Used for disposal Gloves Petriplate Synringes IV sets Foley catheters Sutures implants,prosthesis Glassware Fabrics ,contraceptive devices, cotton swabs
