Sterilization is the process of destruction of all forms of life including spores. So, it's an absolute phenomenon killing all forms of life whereas disinfection is the process of destruction of only the pathogenic microorganisms from inanimate objects. Therefore, sterilization is an absolute condition while disinfection is not.
Antisepsis is disinfection of live tissues and father of
antiseptic surgery is Joseph Lister who introduced phenol during world war for
skin antisepsis sowed start with an order of susceptibility to methods of
sterilization and disinfection.
The most resistant are prions followed by bacterial spores followed by cysts of protozoa followed by non-enveloped viruses’ micro bacteria fungi gram-positive bacteria gram-negative bacteria and the least resistant are on the rather the most susceptible to methods of sterilization and disinfection are enveloped viruses.
Methods of Sterilization and Disinfection
Physical methods include heat radiation and filtration. Heat can be used in two forms of dry heat and moist heat. So dry heat how does it be sterilized or disinfect it denatures proteins it damages or it brings about or creative damage and it raises the level of electrolytes to toxic levels.
Dry heat can be used in the following forms
flaming that is we can pass slides coverslips or mouths of test-tubes bypassing
them through the flame a few number of times and thereby disinfectant next sired
heat that is used for the effective sterilization of articles can be heated to
redness and flame.
So, wearer sterilizing we are making the objected-hot and
there were sterilizing it so straight wires inoculating loop searing spatulas
and tips of forceps can be sterilized by red heat next is an incinerator.
Incinerator
This is the sterilization along with a significant reduction
in volume for final disposal of infectious hospital waste, so how much
reduction in volume are we achieving? It is 80 to 85 per cent reduction in volume.
Infectious hospital waste which can be
put in a vein in an insulator are animal carcasses, human pathological material,
soiled beddings and dressings and cytotoxic drugs.
In an incinerator, there are two chambers a primary and
secondary.
The primary chamber is maintained at a temperature somewhere
around between 650 to 750 degree Celsius and the secondary chamber is maintained
somewhere around 1050 to 1100 degree Celsius.
Hot-air oven
Lastly, we move on to the hot-air oven using dry heat. This
was first introduced by Louis Pasteur and it is useful effective sterilization
of all metallic instruments whether they were sharp onion chopped, forceps case,
sizzle, scalpels etc.
All glassware tests use prepares Petri plates etc. Cotton swabs and oils jellies powders and waxes that are very important or as jellies so paraffin oil is sterilized by petroleum jelly dusting powders.
They are
sterilized by four terrible hot temperature in a hot-air oven. Most often that
is used is 160 degree Celsius for one hour but we can also use 150 degree
Celsius for about two hours. On one 670 degree Celsius for 40 minutes.
Efficacy of a hot-air oven can be sterilized by three methods
physical, chemical or biological.
Physical meaning, we are putting a temperature chart
recorder and really reading it at the end of the cycle. Chemical method issuing
Browns tube and biological method is using spores of either Clostridium tec-9
or using the spores of Bacillus subtilis.
Chemical Methodist Browns tube and biological Methodist
spores of Clostridium thirty-nine or spores of Bacillus subtilis.
Moist heat
The moist heat after dry heat we move on to the moist heat. How
does it kill it denatures and coagulates proteins? moist heat can be used in
three temperatures below hundred eight hundred and above hundred degree Celsius.
Moist heat less than 100 degree Celsius is a classical example
of pasteurization which is used for disinfection of milk.
Pasteurization can be used in holder flash or ultra-high temperature
method.
Holder method is used when we are using moist heat at 63
degree Celsius for 30 minutes.
Flash method is using moist heat at 72 for 15 to 20 seconds
followed by rapid cooling to temperatures less than 13 and ultra-high temperature
is moist heat at 149 degrees Celsius for 0.5 seconds.
How do we trust the efficacy of pasteurization?
We have two methods: Coliform test and Phosphatase test.
In coliform method what we are doing is we are basically testing for the
presence of choline forms like Escherichia coli Klebsiella and Enterobacter
coulis forms, which are normally present in raw meat are easily destroyed by
pasteurization and they’re present in pasteurized product usually indicates
that it is inadequate pasteurization.
What we do is we take our pasteurized milk sample?
We added to the MacConkey broth and overnight incubation we
are going to look for our presence of acid or guests so if Coliforms have been
effectively destroyed by pasteurization. There should be no incident gas that
should appear in the MacConkey broth.
Next test is the Phosphatase test.
Phosphatases an enzyme which is normally presenting raw milk and it gets inactivated when the proper time and temperatures reach for pasteurization. So in this test what we do is we take our passion High's milk sample and we add a substrate for the phosphatase enzyme that substrate is disodium final phosphate. So, after 2 hours of incubation.
Since past
phosphatase enzyme has already been denatured, there is no change in colour
disodium finite phosphate because the faucet is in the sign is missing.
So, no change in colour indicating effective pasteurization. We
get two types of question which is the core most common method for testing the
efficacy and which is the best method.
Best method is the coliform test and most commonly used as
an easy to do test. Which requires just a few hours of incubation, that is the
phosphatase test next is serum bath so Serie or body fluids containing valuable
proteins can be sterilized by heating for one hour at 56 degree Celsius in a
water bath for several days’ vaccine.
But it is used for inactivating non-sporting bacteria for
preparing vaccines and here the temperature is moist heat at 60 degree Celsius
for one hour for several consecutive days.
Moist heat another example is in speciation in a space heater,
using moist heat at 80 to 85 degree Celsius for one hour for three consecutive
days an egg or serum-containing media like LG medium, Loffler serum slope asked
analyzed by inspiration for in speciation.
The basic principle is the first exposure kills the
vegetative forms and when we leave it for the next day the intervals between
that heating is going to lead to the germination of the spores, which are then
killed by subsequent killing.
Fractional sterilization
Lastly, we have temperatures moist heat being used in tidal inaction
which is also called as fractional sterilization. Here we are using moist heat
at 100 degree Celsius for 20 minutes for three consecutive days. Tyndale inaction
is done in a coke and Arnold steam sterilizer. It is used for the sterilization
of sugar solutions, gelatin containing media, DCA and selenite F broth that was
moist heat at hundred degrees Celsius.
Autoclave
Lastly, we have moist heat above 100 degree Celsius. Classical
example of which is an autoclave. The principle of an autoclave is we are using
saturated steam under pressure. The basic principles that generally water boils
at 100 degree Celsius at atmospheric pressures but when water is made to boil in
under pressure and under raised pressures, then it boils at a higher temperature
depending upon the pressure.
In an autoclave, there are two types of an autoclave. One is
which is most often users using moist heat at 121 degree Celsius. here the
pressure inside the autoclave is 15 pounds per square inch.
The other autoclave is when the pressure inside is 30 pounds
per square inch. Here the water is boiling at 134 degrees Celsius, so steam
that is generated is at 134 degrees Celsius and this needs to be kept for just
3 minutes.
Component of Autoclave
Here are the various components of an autoclave. It's the
the vessel is made up of either stainless steel or gunmetal.
It has a perforated tray for steam entry below the poverty
tray there is a heating element we are going to add water which is going to
heat the water and generate steam from it.
The on the perforated tray we are going to place all the
objects then there is laid with a discharge tap or pressure gauge and a safety valve.
What is the use of an autoclave?
It can be used for sterilization of metallic instruments which are non-sharp microbiological culture media of plastic containers pipettes and chips. Efficacy of an autoclave can be tested by physical method temperature chart; recorder chemical method is using Browns tube or we can use Bowie dictates and biological method.
In using the spores of bacillus, sterile thermophiles
so chemical method is Browns tube number one and bevvy dictates and biological
method is using spores of the semester or thermal furnace.
Thus, using dry heat or moist heat, dry heat causes
oxidative damage raising the level of electrolytes to toxic levels and
denaturation of proteins. Whereas moist heat act by just denaturation
coagulation of proteins physical methods. Next one is radiation.
Radiation
We can use radiation in two forms nonionizing or Arising non-ionizing. the classical example is ultraviolet rays, which are generated by tungsten filament, mercury labs. The wavelength of UV rays used for this purpose as 220 to 280 nanometers.
It has a disadvantage, they have very poor
penetrating power and do not kill spores, so they are only used for surface
disinfection of hospital corridors, hospital wards or laboratories or through
biosafety hoods.
Since they have no penetrating power, they are only used for
surface disinfection.
Next type of radiations are ionizing radiations. The classical example of this is gamma rays. The use of gamma rays is also called as cold
sterilization and these are generated by the nuclear disintegration of
radioactive isotopes of cool Birds or cobalt or caesium.
Mechanism of action of gamma rays is by causing DNA damage.
These are highly penetrating and they even kill spores, so they would be
sterilizing rings. The gamma rays aroused
for the sterilization of
- Disposable syringes,
- Gloves,
- Petri plates,
- Hormones glassware,
- Fabrics,
- Carded,
- Implants,
- Pacemakers
- Orthopaedic implants
- Sutures, Canada's as well as Foley's Capita Land efficacy.
Testing of gamma radiation is done by spores of bacillus.
Filtration
Next physical method is using filtration. These are used for removing microbes from solutions which are heat sensitive such as serum antibiotic solution, sugar solution, urea solutions and vaccines. When we want to remove the microbes, we are going to use penetration pore size of standard backing filters range from 0.2 to 0.45 microns.
When we want to just filter out the
bacteria from the seats and every solution, we could use though that pore size
that is the range of bacterial filters but if it is just asked as a single
value generally standard bacteria filters have a pore size of 0.45 microns.
The various types of filters used on earthenware filters
which are made up of either porcelain or diatomaceous earth. These are shaped
in the form of candles and examples of these include mandala filters and
pasture Chamber land intermeddler and Pasteur Chamberlain filters.
Forestall filters are made up of magnesium trisilicate and these are shaped in the form of disks examples of which are seed filters next type of filters are centred glass filters which are made by the fusion of powdered glass.
Again, they're shaped in the form of disks and lastly, we have most commonly used presently membrane filters which are either made up of cellulose esters or polycarbonate these membrane filters are of two types depending upon how the poles have been produced in the membrane capillary port. Where the poles are produced by radiation and labyrinthine pour that has made here the poles are being made by first evaporation of solvents.
Example of membrane filters is
milli pour. Presently these are the most commonly used filters this is the first
part of sterilization and disinfection.
This is all about the method of sterilization and disinfection.