Sterilisation Flashcards
Dry heat methods
A. Dry Heat:
1) Red heat
Direct heating on the flame until redness Used in sterilization of inoculating wires or points of forceps
2) Flaming
Temperature
Uses:
Types of aut
Sterilization
By passing the article through the flame without redness.
Used in sterilization of scalpels, needles, mouth of culture tubes and glass slides.
3) Incineration:
Used for the destruction of dead animal bodies or contaminated disposable
[articles
4) Infra-Red Rays
The rays are directed to the object, and temperature rise up to 180°C within seconds. Used for sterilization of metal instruments
5) Hot air over
The oven is electrically heated, provided with thermostat and a fan to ensure rapid uniform heating
Used for sterilization of:
All glasses eg. test tubes, Petri dishes, flasks and glass syringes. Instruments: as forceps, scalpels and scissors.
Dry material in sealed containers as fat, olls and powders.
Holding time.
160 °C for two hour.
-180 °C for one hour.
Moist heat 2 methods
Moist Heat:
1) Below 100 °C:
Pasteurization of milk:
By heating at.63 °C for 30 minutes and rapid cooling. This kills all non sporing bacteria as bovine T.B.
Sterilization of serum:
By heating for 1 hour at 56 °C for 3 successive days (Tyndallization) Sterilization of vaccines:
In special water bath “vaccine bath” for 1 hour at 60 °C.
2) Boiling at 100 C
• Boiling at 100°C for at least 10 minutes is sufficient to kill all non sporing and
most of the sporing organisms. Used for sterilization of pipettes, rubber stoppers, scalpels, forceps, scissors, glass and metal syringes.
Uses and types of autoclave
Uses:
Sterilization of surgical objects as dressings, towels, and surgical instruments as scissors, clamps, arteries, retractors, etc.
Types of autoclaves:
⚫ Simple laboratory autoclave,
Downward displacement autoclave.
High pre vacuum autoclave.
HEPA
high effeciency particle arrest Used in - icu - high risk operative rooms - isolation room - safety cabinet in microbiology lab
Browne’s tubes. Bowie Dick tape
:
Used for heat- an
⚫ Give an immediate indication of a successful or non- successful sterilization
Browne’s tubes are glass tubes that contain heat sensitive dyes. These change
colour after sufficient time at the desired temperature.
Before heat exposure, the contents of the tube appear red. • As heating progresses, the colour changes to green.
Only when the tube is green sterilization conditions can be considered adequate. ⚫ Bowie Dick tapeis applied to articles being autoclaved.
• Before heat exposure, the tape is uniformly buff in colour.
After adequate heating, the tape develops dark brown stripes.
Physical sterilisation control
Physical: measuring device control (temp., time, pressure).
Biological sterilisation control
:
E
Bacillus stearothermophilus spores.
Survives steam heat at 121°C for 5 min. and is killed at 121°C in 13 min.
• Validate and determine the adequacy of steam or chemical vapor sterilization
⚫ Bacillus subtilis spores.
⚫ Validate and determine the adequacy of ethylene oxide or dry heat sterilization.
Uses of uv sterilisation and source
Sterilization of operating theatre..
Sterilization of inoculation chamber for viruses.
Sterilization of water.
Mercury lamp
b)-Ionizing irradiation sterilization
:
It is gamma rays of an isotopic source as cobalt 60.
Uses Sterilization of an article not stand the heat as rubber catheters, cat gut or plastic syringes.
Low temp sterilisation
Low Temperature Sterilization
Used for heat- and moisture-sensitive medical devices
Ethylene oxide gas
. Highly toxic inflammable gas.
used for heat-labile equipment, fluids, and rubber, etc., a is a relatively expensive process.
Hydrogen peroxide gas plasma
Plasma is the 4th state of matter, produced in strong electromagnetic field.
The plasma is combined with hydrogen peroxide
Properties of an ideal disinfectant
:
- Broad spectrum: should have a wide antimicrobial spectrum.
- Fast acting: should produce a rapid kill. 3. Not affected by environmental factors: should be active in the presence of
organic matter (e.g., blood, sputum, feces) and compatible with soaps,
detergents, and other chemicals encountered in use. 4. Nontoxic: should not be harmful to the user or patient.
- Surface compatibility: should not corrode instruments and metallic surfaces and should not cause the deterioration of cloth, rubber, plastics, and other materials.
- Residual effect on treated surfaces: should leave an antimicrobial film on the treated surface.
- Easy to use with clear label directions.
- Odorless: should have a pleasant odor or no odor to facilitate its routine use.
- Economical: should not be prohibitively high in cost.
- Solubility: should be soluble in water.
- Stability: should be stable in concentrate and use-dilution.
- Cleaner: should have good cleaning properties.
- Environmentally friendly: should not damage the environment on disposal.
High level disinfectant
3- High-level disinfectant (HILD):
Destroys all vegetative bacteria, fungi, enveloped and nonenveloped viruses and some bacterial spores
Examples:
Hydrogen Peroxide
Used as mouth gargle and antiseptics to clean wounds.
Gluteraldehyde (e.g.Cidex)
Very potent disinfectants, which can be highly toxic. Use them only under trained supervision in a well-ventilated setting and with appropriate personal protective equipment. Formaldehyde (eg. Formalin, Formadon)
used as a disinfectant both in the liquid and gaseous states.
Peracetic Acid
Formaldehyde should be handled as a potential carcinogen which limit its role in sterilization and disinfection processes Used in automated machines to chemically sterilize medical, surgical, and dental
(e.g., endoscopes, arthroscopes).
Intermediate level disinfectant
2- Intermediate-level disinfectant (ILD):
Destroys all vegetative bacteria, including tubercle bacilli, enveloped and some nonenveloped viruses, most fungi, but not bacter spores.
Examples
Alcohols (eg Ethyl alcohol, Isopropyl alcohol).
Alcol is me commonly used topical antisepties. They are also used to disinfect the surface of medical equipment Hypochlorites (e.g.Clorox)
Readily available as “household bleach”, widely used as surface disinfectant Used as water disinfectant lodine And Iodophor Disinfectants (e.g.Betadyne, Povidone)
O used as skin antiseptic Disinfection of blood culture bottles and medical equipment such as thermometers, and endoscopes.
Low level disinfectant
1- Low level disinfectant (LLD):
Destroys all vegetative bacteria (except tubercle bacilli), enveloped viruses, and some fungi, but not bacterial spores.
Examples:
Phenol group: (eg. Lysol).
Phenol is commonly found in mouthwashes, scrub soaps, surface disinfectants, and household disinfectants.
Phenol 5% used as disinfectant of stool in typhoid or sputum in T.B Quaternary Ammonium Compounds (e.g Roccal-D, Quintacide.)
The quaternary ammonium compounds are widely used as surface disinfectants but are
contraindicated as antiseptics
Dental instrument spalding classification
Dental instruments:
- Critical items:
critical items confer a high risk for infection if they are contaminated with any
microorganism. penetrate mucous membranes or contact bone, blood stream, or other normally sterile
tissues.
heat sterilize (steam) between uses or use sterile single-use, disposable devices.
examples include surgical instruments, scalpel blades, periodontal scalers, and and surgical dental burs heat-sensitive objects can be treated with eto, hydrogen peroxide gas plasma
if other methods are unsuitable, sterilized by liquid chemical sterilants.
- Semi-critical Items:
contact mucous membranes but do not penetrate soft tissue.
heat sterilize or high-level disinfect.
examples: dental mouth mirrors, amalgam condensers, and dental handpieces
3. Non-critical Items:
contact intact skin.
clean and disinfect using a low to intermediate level disinfectant
⚫ examples: x-ray heads, facebows, pulse oximeter, blood pressure cuff.
