Control and destruction of microbes
methods of control a) Principles and methods of microbial
and destruction of control
microbes -Sterilization
-Disinfection the CSSD
-Chemotherapy and antibiotics
-Pasteurization
b) Medical and surgical asepsis
c) Bio-safety and waste management
Definitions
(1) Sterile :-Free from micro-organism of any kind.
(2) Sterilization:– Process of killing or removing microbes including pathogenic, non-pathogenic, spores.
(3) Disinfection :- It is the process of removing or killing pathogenic organisms which does not necessarily include non-pathogenic organisms.
(4) Disinfectant :- An agent which is infection free. Has bactericidal action.
(5) Sepsis :- Growth of pathogenic in living tissues is called sepsis.
Asepsis :- Absence or prevention of growth of pathogenic organisms in living tissues is called asepsis.
Antiseptic :-Chemical substance which is used to prevent infection by inhibiting the growth of harmful micro-organisms.
Fumigation:– The destruction of organisms through a gaseous agent is known as fumigation.
Principles & Method of microbial control Microbes
Microbes are almost everywhere. But we are not conscious of it. Their presence is excessive in hospitals where the patient leaves a large number through their urine, stool, sputum, secretion.
Apart from this, microbes are also present in blood, food, water, sewage, air and soil etc.
Since they are found in many ways, different methods have been developed to destroy them.
Which includes physical and chemical methods, which are used according to the knowledge and requirements of the operator.
A person’s personal comforte also depends on his knowledge of this matter and the method of controlling the microbe.
Like, Environment, Equipments, Cleanings, Food & kitchen, Body care etc. There are three main reasons for destroying or inhibiting micro-organisms
(1) To prevent infection and transmission of disease.
(2) To prevent decomposition and spoilage of food.
(3) To prevent contamination of material used in culture.
Physical agents
(1) Heat
(2) Sunlight
(3) Cold (law temp.)
(4) Drying or Dessication
(5) Radiation
(6) Filtration
(7) Sound waves and Ultrasonic vibration.
Chemical agents
(1) Phenol and cresol compounds
(2) Alcohol
(3) Halogens (Iodine and chlorine compound)
(4) Dyes
(5) Aldehydes
(6) Acids
(7) Alkalies
8) Gases
9) Metallic salts
(10) Oxidizing agents
(11) Surface active agents.
Physical Agents
Heat :- Heat is a trusted most effective economic and wildly used agent.
The effect of heat on microbes depends on four factors.
1.Type of Heat (Dry or Moist Heat)
3.Environment Factors
Dry Heat
(i) Direct flaming :-
Platinum, copper and other metals were used to sterilize wires, points of forceps, needles.
In this method the object is kept in the flame till then. That is until it becomes red hot
If there is protein material or fat on the tip of foceps or on the object, then it should be dipped in chemical disinfectant first.
This method is also used for glass slides. Glass articles are quickly passed through the flame. But they are not kept till red.
(ii) Burning or Incineration
Infected laboratory materials, contaminated swabs, paper sputum cups, dressings, books, magazines, clothes, mattresses, etc. are used for hospital waste disposal.
It is safe, easy cheap and excellent method, incinerators are made for this purpose in hospitals.
Conti……………
In this method, oven is used to sterilize different items.
Like instruments, glass-wares, bandages, cotton swabs, dusting powder, solution which has less amount of water.
This cannot be used for alcohol or other solutions.
The oven is a double coated chamber. Which is operated by electric or gas heat.
Thermostat mechanism is used to control the temperature.
Material is kept at 180°C temperature for 30 minutes, 160°C – 60 min and 140°C – 90 min without pressure.
The oven door should be kept closed during heating (to maintain temp.) and should not be opened for 2 hours after heating, because there are chances of glass ware crack due to sudden cooling.
(B) Moist heat
Below 100° C & 100° C and abovt100 C temperature are used for different objects.
Temperature below 100*C
(i) Pasteurization of milk
Discovered by Pasteur in 1860.
It was first used in wine beer.
But currently it is used for milk.
In pasteurization 62″ C for 30 minutes (holder method) or 121° C for 15 10 20 seconds (flush method) in both high temperature, cooling effect is given immediately at 13 or less temperature.
Pasteurization can kill all pathogenic bacteria like mycobacterium tuberculosis, salmonella typhy bracella etc.
So that milk can be made safe for drinking, it is not the method of sterilization, but the organism that remains after pasteurization. It is harmless.
Temp < 100° C is also used for many other objects. So that it can be disinfected. Like eating utensils, nurturing equipments are cleaned with hot water.
80 C for 15 minutes, Destroys the vegetative forms of all bacteria.
Temperature at 100′ c
(i) Boiling (100° C) :
Boling is a very simple method of disinfection.
Most of these vegetative forms of bacteria are killed within 10 minutes, but the spores survive.
Bolling is a suited method for sterilizing syringes, for glass ware and for clothes of infectious patients and articles that are not damaged by bolling.
It is not recommended for instruments used in opreration because it simply disinfects, not sterilizes
There are different types of boilers for bolling in the market which can be used for different purposes. Any houseware that can be covered can also be used as a sterilizer.
(ii) Fractional sterilization (Intermittent sterilization)
It is also called Tyndallization as it was developed by British scientist John Tyndall.
In this process 100* C temp. 20 min. until required.
And this is done for 110 4 days.
In other words, repeated heating at day intervals (12 to 24 hrs) is used, it also destroys vegetative forms bacteria and spores.
In the third heating, almost all remaining organisms are destroyed, except for the preparation of culture media, this method is not used.
Arnold, a German bacteriologist developed a special apparatus called Arnold steam sterilizer, in which steam is used without pressure.
Temperature above 100° C (Steam under pressure) Autoclaving
Heat under pressure is a practical and useful agent in sterilization.
In this method 15 lbs pressure and 121° C temp. 30 minutes is required for sterilization.
Pressure does not kill organisms, but steam under pressure can do the job.
Time is how much bulky material to sterilize. Depends on it. This is considered one of the best method of sterilization. Which destroys all bacteria and spores.
The equipment used for this process is called an autoclave machine, which is similar to a home pressure cooker.
AUTOCLEAVE MACHINE
Autoclave is a double walled metal instrument.
which has an airtight chamber. They usually have 2 gauges.
It reads the steam presser of the outer inner chamber.
It has a safety valve to prevent explosion due to high pressure, which releases steam as the pressure increases.
There is also an exhaust valve to take out the steam of the inner chamber.
There is also a valve to send steam from the outer chamber to the inner chamber.
Some autoclaves also have thermometers fitted inside the chamber.
After keeping the object on the plate inside the inner chamber, after closing the lids tightly, the heating is turned on.
15 lbs/inch, 120°C 30 minutes autoclave benefits are. That can kill the organism including the spore.
And fixed temperature and pressure of steam can be maintained. This method can be used to sterilize culture media, rubber goods, linens, dressing, syringes and…Inruments and many other important consumables can be used in sterilization. It is one of the best, most practicable, dependable method of sterilization.
(2) Sunlight
Sterilization is done by this natural method in water tank, rivers, lakes etc.
Among the methods used at home, this is the best method of disinfecting clothes. (Mattresses, clothes etc.)
Many types of bacterial spores and microbes can be removed by direct exposure to sunlight.
Tuberculosis germ can be killed by a few hours of sunlight exposure.
Germicidal action in sunlight is attributed to ultra violet and infrared rays in sunlight.
Germicidal action in sunlight is attributed to ultra violet and infrared rays in sunlight.
(3) Cold (law temperature)
Diseases like Meningitis and gonorrhoea can be killed by micro-organisms cold.
But not all bacteria can be killed by law temperature, e.g. Typhoid bacilli cannot be killed even in frozen state.
Cold usually prevents the multiplication of ordinary bacteria.
Hence it is used for preservation of food.
Microbial activities can be delayed due to cold. There is no reliable or reliable method for disinfection or sterilization.
4) Drying or Dessication
Unrealizable method is. Spores can survive in dried objects for months or years.
Germs of cholera, pneumonia, diphtheria, whooping cough which have been seen sensitive to cold.
While drying has no effect on yeasts, molds and most bacteria and they can survive for months.
(4) Radiation
The effect of radiation energy on microbial cells is caused by the death of microbes. Two types of radiation are used.
(1) Non-ionising agent includes infrared, ultraviolet radiation and
(2) Ionising uses x-ray, Gamma rays, Cathode rays etc.
Infrared radiation 190°C temp. Used for 10 minutes.
The heat generated by it is sufficient for killing micro-organisms.
Ultraviolet radiation is useful in disinfection of O.T., hospital wards, swimming pool, rooms etc.
Apart from the energy law in these rays, the penetration power is also poor.
Can be produced artificially easily. It can be produced by passing electric current through a special type of tube or germicidal lamp.
Ionising radiation is produced with the help of high voltage generators. This method is expensive,
Filtration
Used for materials that can be damaged by heat.
Mostly used in pharmaceutical fluids and bacteriological laboratories.
There is a mechanical method of micro-organisms without changing the chemical properties of the substance
Different types of remove filters are used in the laboratory. In which materials like candles, cellulose membrane, porcelain etc. are used.
The virus cannot be removed from it.
(7) Sound and Ultrasonic vibrations
Bacteria can also be killed through rapid vibration. which are sound waves. There are many apparatuses available in the market that can provide sufficient sound waves intensity – sufficient time.
These waves destroy cells and cell walls. This method is practical for sterilization or disinfection.
CHEMICAL STERILIZATION
Many chemical agents available in the market have antiseptic and disinfectant properties.
Those who exhibit antimicrobial activities.
But their mode of action is different. Many enzymes destroy the protein of the cell through oxidation and radiation.
There is no single chemical available that is completely effective against all types of microbes.
Many chemical agents are used in hospitals, homes and industries.
a) Phenol and cresol compound
These are Coaltar derivatives, used in hospitals for hundred and one years.
Phenol (carbolic acid) was first used by Lister in 1865. (The father of antiseptic surgery) Phenol in pure form is not used as it is very expensive and not effective.
It is usually used in the form of a 3% solution.
Used to disinfect instruments, furniture, floors, walls etc
There are many derivatives of phenol such as cresol, tricresol, Lysol, dettol, chlorophenols, chloroxyphenols, hexachlorophene, chlorohexidine etc. are useful against gm+ve and gm-ve bacteria.
(b) Alcohols
Many alcohols have disincentive properties.
But ethyl alcohol and isopropyl alcohol are commonly used
A concentration of 70% is used. It kills the bacteria by spoiling or destroying the protein of the bacteria cell.
They are not effective against spores and viruses.
Although methyl alcohol has less bacteriocidal action, it works well against fungal spores.
It is highly toxic and inflammable
Commonly used to disinfect incubators in laboratories.
(c) Halogens (Iodine and chloride compounds)
Iodine is very old and most effective germicidal agents
It has been in use for more than a hundred years.
It is commonly used for skin preparation.
Iodine (as a disinfectant) is not used in concentrated forms because it burns tissue and forms blisters.
Its week form is used to treat infected wounds and inflamed mucous surface especially throat, skin, disease and before operation.
Most common available chlorine compounds are bleaching powder (chlorinated lime), chloramines and hypochlorite.
It is available in powder and liquid forms with different concentrations.
Bleaching powder is used for disinfection in drinking water, swimming baths, foods & dairy industries.
Bleaching powder is used for disinfection in drinking water, swimming baths, foods & dairy industries.
(d) Dyes
Due to the antimicrobial activities of dyes, they are used excessively in skin and wound infections and laboratories
It is bacteriocidal and sporocidal.
A 40% formaldehyde solution in water is known as formalin.
It is used for fumigation of rooms, wards and laboratories.
10% formalin is used to preserve the specimen. It can be used in very carefully controlled conditions.
It is also required for disinfection of Asputum, faeces, instruments, clothes, bedding, books, furniture etc.
Since Formaldehydes irritate the skin, eyes, nose, throat, and mucous membrane, control of the environment is necessary.
It is toxic by inhalation and loses its effect if exposed to ambient air.
Acids
Acetic acid has been used for years in the prevention of Pseudomonas infection that occurs in food.
Although boric acid is a weak antiseptic, it is used for wound infection and inflammation of the mucous surface.
(f) Alkalies
Sodium hydroxide and lime have powerful germicidal action.
Formaldehyde is used for specimen preservation.
Gases
(Many things are sterilized with the help of chemical agents like gas.
Gas is released in a specific area. Many biological materials (test tubes, petridishes, laboratory equipments, machines, clothes, plastics, soil etc.) are sterilized by gas.
Formaldehyde is used to disinfect rooms along with potassium permanganate.
Ethylene oxide is also used as a gas. Which can kill all kinds of micro-organisms and spores.
Used in 3% concentration with Co2 or N2. Used for metal glass, paper and plastic materials. Ethylene oxide is explosive and toxic, so precautions must be taken.
h) Metallic salts
(Inorganic or Organic) Metal compounds al mercury, silver, copper, arsenic and zinc are used in very law concerntration.
The combination of metal with the protein of the organism causes cell death. Not in much use
Oxidising Agents
(KMn04, H2O2Potassium permanganate is used as an antiseptic in skin infection. H2O2 is not a good disinfectant but is useful for wound treatment.
Surface active agents
A substance that reduces surface tension is called a surface active agent.
It usually mechanically removes micro-organisms.
Soap is a very good surface active agent used for skin cleaning.
CHEMOTHERAPY AND ANTIBIOTICS
Chemotherapeutic drugs are used for prevention and treatment of infection in chemotherapy.
There are many chemotherapeutics, among the most commonly used drugs are sulphonamides. are obtained from living organisms.
These drugs have bacteriostatic and bacteriocidal action.
Bacteriostatics only inhibit bacterial growth. While bacteriocidal does the work of killing bacteria.
Source and action of antibiotics
Antibiotics are obtained from living organisms.
It is produced by bacteria, fungi, actinomycetes, streptomycetes or plants.
Some organisms produce more than one antibiotic.
Sometimes more than one type of organism produces antibiotics.
These antibiotics have bacteriocidal (e.g. penicillin) or bacteriostatic (e.g. chloromphericol) action.
Antibiotics are made during the culture process during the growth of microbes in culture media. Later antibiotics are obtained by filtering the culture.
Antibiotics differ in their route of administration. Many are used in the form of ointments, many in oral form and others in injection (i.v. /i.m. /sc /) form.
Many antibiotics are effective against gm+ve bacteria and many are effective against gm-ve bacteria.
There are also antibiotics that prove useful against both gm+ve and gm-ve types of bacteria. Antibiotics that give a wide range of activities are called broad spectrum antibiotics.
Mycostatin, Actidione antibiotics have antifungal action. Hence it is used in laboratories to protect cultures from fungi. Penicillin, streptomycin, terramycin, aureomycin, chloromycetin, erythrocin are examples of antibiotics.
These are known as miracle drugs. Their disadvantages and hypersensitivity are also seen, in which allergic reaction like skin rashes, joint pains, enlargement of lymph nodes, a fall in W.B.C. counts, haemorrhages etc. are seen.
Almost every antibiotic reduces the normal flora and causes deficiency of Vit.B.
Sometimes changes are seen in the mucous membrane. It is necessary to check the sensitivity of the organism before using antibiotics.
PASTEURIZATION
Pasteurization is a method of sterilizing milk. In which only harmful bacteria are destroyed. But lactic acid and necessary organisms are not destroyed. There are few changes in the protein and sugar in the milk. There are three methods of pasteurization.
(1) Holder or wet method
In this milk is heated at 62 C for 30 min. It is then rapidly cooled to less than 5°C.
T.B. and for Typhoid organisms is heated at 121’c for 15 to 20 seconds. It is called flash method.
(2) H.T.S.T. (“Temp, ↓ Time)
Milk is rapidly heated to 72°C and cooled to less than 5°C.
(3) UHT method (Ultra high temp.)
Milk as high temp as 121’c to 150’c. It is heated and then cooled very quickly. Phosphatic method is used to check the pasteurization of milk. Phosphate is present in raw milk. which is destroyed during pasteurization.