Sterilization And Disinfection Flashcards
Sterilization definition
Removal of pathogens including spores
Disinfection definiton
Removal of Pathogens but not spores
Asepsis definition
To make body surface/skin/wound free of mirco-organisms
Sterilization methods are divided into
Physical
Chemical
Physical Sterilization methods includes
Heat
Filtration
Radiation
Chemical sterilization methods includes
Alcohol
Aldehydes
Phenols
Halogens
Oxidizing agents
Plasma sterilization
Gas sterilization
Heavy metal salts
Surface acting agents
Dyes
Heat method of Sterilization is divided into
Dry heat
Moist heat
Examples of Dry heat methods
Candle
Flame burners
Sunlight
Hot air oven
Incinerator
Mechanism of Dry heat Sterilization methods
CODE
Charring
Oxidative damage
Denaturation of proteins
Elevation of electrolytes
Hot air oven temperature and duration
160°C for 2 hr
For every 10° increase in temperature - time should be decreased by half
For Ex. 170°C × 1hr, 180°C x 30 min
Hot air oven is used to sterilize
Glasswares
Cotton swabs
Wax, oils, powder gels
Dusting powder
Greasy paraffin wax
Metallic (sharp and non sharps)
Physical control of Hot air oven
Temperature monitoring by thermocouples
Chemical control of Hot air oven
Brownies tube (green spot)
Biological control of Hot air oven is done by
C. Tetani or Bacillis subtilis/atropheus
Incinerator is used for sterilization of
Hospital waste
Human anatomical waste
Animal carcasses
Expired Cytotoxic drugs
Temperature maintained in Incinerator
2 chambers - 700-800°C and 1000-1100°C
Mechanism of Moist heat Sterilization
Coagulation and denaturation ot proteins
Which Heating sterilization method is considered better - Dry or Moist heat
Moist heat
Moist heat Sterilization methods classification on basis of temperature
1) Below 100°C - IPL100 - Inspissation, Pasteurisation, Vaccine water bath
2) At 100°C - BAT - Boiling and Tyndalisation
3) Above 100°C - Autoclave
Methods or Milk Pasteurisation
Holder method
Flash method
Ultra high temperature method
Holder method of milk Pasteurisation temperature and duration
63°C for 30 minutes
Temperature and duration of Flash method of Milk Pasteurisation
72°C for 20 seconds - Rapidly cool it to <13°C
Ultra high temperature method of Milk Pasteurisation
149°C for 1-2 sec
Which method of Milk Pasteurisation is better
Flash method as it kills Coxiella brunetti
Tests for efficacy of Pasteurisation
1) Phosphatase test - On adding substrate - no color change (enzymes denatured)
2) Coliform test - No growth on MacConkey agar
Temperature and duration for Inspissation method
80°C for 20-30 min for 3 consecutive days
80-80-80
Inspissation method is used for sterilization of
Lowenstein Jensen media
Loeffler’s serum slope
Temperature and duration of Vaccine water bath method and uses
60°C for 1 hour
Bacterial vaccines are heat inactivated
Temperature and duration for Boiling method
At 100°C for 15 min
Doesn’t kill spores
Temperature and duration for Tyndalisation method of Sterilization
At 100°C for 20 min for 3 consecutive days
Kill spores
Tyndalisation Method is used for sterilization of
Used for media with gelatin/sugar
TCBS
XLD
DCA
Selenite F broth
Temperature and duration of Autoclave method
121°C for 15 min for 15psi
To kill Prions - 134°C × 1.5 hrs
Control used for Autoclave
Bacillus Stearothermophilus
Uses of Autoclave method
Instruments (non sharps)
Aprons
Sutures except catgut sutures
Media except LJ and LSS
Sputum (prior to descending)
Average Pore size in Filtration method
0.22 micron
Types of Filtration methods
Depth filters
Membrane filters
Depth filters include
Candle filters
Seitz filters - not used
Glass filters
Membrane filters includes
Cellulose acetate
Cellulose nitrate
Uses of Filtration method of Sterilization
For heat sensitive substances
Vaccine
Antibiotics
Serum
Toxins
Sugar solutions
Control of Filtration method is done by
Brevendimonas diminuta (chota chota)
Serratia
HEPA full form and its efficacy
High efficacy particulate air filter
99.97% efficacy
ULPA full form and it’s efficacy
Ultra low particulate air filter
99.999% efficacy
Types of Radiation methods of Sterilization
Ionizing (Cold radiation)
Non ionising (Hot radiation)
Penetrating power of Ionising and Non ionizing radiation methods
Ionizing - High penetrating power
Non ionizing - low penetrating power
Which radiation method is Sporicidal
Ionising - Sporicidal
Non ionising - Bactericidal only
Ionising radiation includes which rays
X rays
Gamma rays
Cosmic rays
Non ionizing radiation includes which rays
UV Rays
Infrared Rays
Uses of Non ionising radiation method
OT Fumigation
Biosafety cabinet
Types of Alcohol used for Sterilization
Ethyl alcohol (70%) - Spirit
Isopropyl alcohol (70-80%)
Thermometer and Stethoscope are sterilized by
Isopropyl alcohol
Aldehydes used for Sterilization
Formaldehyde
Formalin
Glutaraldehyde
Ortho-phthaldehyde (OPA-Cidex)
Formaldehyde uses
Gas - OT Fumigation
10% NBF - For fixation of L/M
Formalin uses
Preserve Specimens (human)
Duckering - killing bacillus anthracis spores from animal wool
Glutaraldehyde uses
Also known as CIDEX
Used to sterilize Bronchoscope and Laryngoscope
Glutaraldehyde/CIDEX is activated by
Alkalinization - active for 14 days
Ortho-phthaldehyde (Opa-Cidex)
0.55% Solution
Cystoscopes etc
No activation needed and more stable
More Bactericidal activity
Carbolic acid is first used by
Joseph Lister - Father of Antiseptic surgery
Mechanism of Aldehydes
Cross Linking and alkylating the molecules
Mechanism of Phenols for Sterilization
Protein precipitation and cell membrane damage
Use of Phenol
For sterilization of Sharp instruments
Types of Phenol
Phenol (5%)
Cresol (1-3%)
Lysol (2-5%)
Savlon consists of
Chlorhexidine + Cetrimide
Dettol consist of
Chloroxylenol
Mechanism of action of Halogens
Oxidizing agents
Iodine uses
Tincture iodine (2% iodine) - For skin Antiseptic
Providone iodine - Betadine (iodophore) - has residual action (better)
Chlorine uses
1% sodium Hypochlorite - for blood spills
<10ml spill - 1:100
>10ml spill - 1:10
Oxidizing agents includes
H2O2 - strong oxidizer, free radical injury
Paracetic acid - <1% is effective for spores
Most effective concentration of H2O2 and concentration needed for spores
3-6% - most effective concentration
10% - needed for spores
Meaning of Plasma in Plasma sterilization method or Sterrad
Plasma - gaseous state containing ions and electrons
Process of Plasma sterilization or Sterrad
UV photons used
Vacuum
Low temperature
H202 chemical is present
Advantages of Plasma sterilization method
No toxic residues
Short cycle time - 75 mins
Uses of Plasma sterilization method
Surgical instruments eg - Arthroscope, Urethroscope etc
Control of Plasma sterilization method
Bacillus Stearothermophilus
Gas used for Gas Sterilization
Ethylene oxide
Mechanism of action of Gas sterilization
Microbicidal
Sporicidal
Side effects of Gas sterilization
Highly inflammable
Highly irritant
Highly explosive
Mix it will inert gases (3%)
Factors affecting Ethylene oxide
Concentration
Humidity
Temperature
Entire cycle may take 18-24 hrs
Uses of Gas sterilization
Pre packed syringes
Cardio pulmonary machines
Control of Gas sterilization
Bacillus Globigi
Heavy metal salts used for Sterilization
1% Silver nitrate - Opthalmia neonatarum
Silver sulphonamide creams - Burns
Mercury (Thiomersal) - antisera, vaccines
Mechanism of action of Surface acting agents in Sterilization
Lowers the surface tension
Anionic surface acting agents
Detergent like action
Weak antimicrobial activity
Ex. Soap
Cationic surface acting agents
Quaternary ammonium compounds
More effective against Gram +ve than gram -ve bacteria
Ex - Cetrimide (Savlon)
Amphoteric surface acting agents (TEGO Compounds)
Anionic + Cationic
Detergent + antimicrobial activity
Used as Antiseptic in dental procedures
Dyes used for Sterilization
Aniline dye
Aeridine dye
Aniline dyes
More active against gram +ve
Crystal violet
Gentian violet
Malachite green
Not active against Tb
Aeridine dye
More active against Gram +ve
Can act in presence of organic waste
Aeriflavine
Proflavin
Testing of disinfectant done by
Phenol coefficient test/Rideal walker test
Chick martin test/Modified Rideal walker test
Kelsey and Sykes test/Capacity test
Kelsey and Maurer test/Inuse test
Phenol coefficient test/Rideal walker test
Highest dilution of disinfectant needed to kill S. Typhi broth divided by Highest dilution of phenol needed to kill S typhi broth more than 1
Disadvantage of Phenol coefficient test/Rideal walker test
Don’t know efficacy with organic matter
Chick Martin test/Modified Rideal walker test
Test disinfectant in presence of organic matter (yeast, Soil, feces)
Kelsey and Sykes test/Capacity test
Capacity of disinfectant to be used in increasing microbiological load
Kelsey and Maurer test/Inuse test
Done to test for contamination of disinfectant
Reality testing
Organisms with decreasing order of Resistance
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Prions - most resistant
Cryptosporidium oocyst
Bacterial spores
Mycobacteria
Giardia cyst
Small non enveloped virus
Trophozoites
Gram -ve bacteria
Fungi
Large non enveloped viruses
Gram +ve bacteria
Enveloped virus - most susceptible
Which organism is most resistant to Sterilization
Prions
Which organisms are most susceptible to Sterilization
Enveloped virus
Spaulding classification
Critical device
Semi critical device
Non critical device
Non critical surfaces/medical equipments
Critical device examples and disinfection
Penetrate/Enter sterile devices
High level disinfectant/chemical sterilant
Semi critical device and disinfection
Come in contact with mucus membrane
HLD
Non critical devices and disinfection
Come in contact with skin
Intermediate/LLD
Non critical surfaces/medical equipments and disinfection
Computer,desks,tables
LLD
Intermediate level disinfectant includes
Isopropyl alcohol
Iodophore
Phenol
Low level disinfectant includes
Chlorhexidine
Quaternary ammonium compounds
Sporicidal agents
EFGHAPPPT
Ethylene oxide
Formaldehyde
Glutaraldehyde
H202, Hot air oven, 1% Hypochlorite
Autoclave
Per acetic acid
Plasma sterilization
O-pthalic acid
Tyndalisation
Sterilization of Prions
Critical device - Treat it with 1N NaOh and 121°C for 30 min then routine Sterilization
