Disinfection is defined as the destruction of all pathogenic organisms or organisms capable of giving rise to infection.
Disinfectant or germicide is a substance which destroys harmful microbes (not usually spores) and thus prevent the transmission of disease.
Antiseptic is a substance which destroys or inhibits the growth of microorganisms. A disinfectant in low concentrations act as an antiseptic. Antiseptics can be safely applied on living tissues.
Detergent is a cleaning agent which acts by lowering the surface tension e.g. soap.
Deodorant is a substance which suppresses bad odor e.g. bleaching powder.
Types of Disinfection
Disinfection can be classified as: 1. concurrent disinfection 2. terminal disinfection 3. recurrent disinfection
1. Concurrent disinfection:
It is the disinfection of the infectious agent as soon as it is discharged from an infected person. It also applies to disinfection of articles soiled with such discharge. Concurrent disinfection is done for urine, feces, clothes, dressings etc. throughout the course of illness.
2. Terminal disinfection:
It is done when the patient has died or has been discharged from the hospital. It is rarely practiced at present.- Terminal cleaning is sufficient.
3. Recurrent (prophylactic) disinfection:
It is prevention of an infection by chlorination of water, pasteurization of milk, hand washing etc.
Classification of Disinfectants
1. Natural disinfectants
2. Physical disinfectants
3. Chemical disinfectants
Air and sunlight.
Heat and radiation.
Lime, Potassium permanganate, Bleaching powder, Formalin, Phenol
Air kills microorganisms by drying them.
The ultraviolet rays of sunlight kill microorganisms.
It can be produced by: 1. burning 2. hot air 3. boiling 4. steam.
i) Burning can disinfect dressings and swabs.
ii) Hot air can disinfect dressings, swabs and glassware’s.
iii) Boiling kills microorganisms including spores. Limón, utensils, instruments and glassware’s can be sterilized by boiling.
iv) Steam dustpans microorganisms and spores. Sterilization of instruments and dressing’s is done by steam.
It can be done by noising radiations and ultraviolet light.
i) Ionizing radiations: They have a great penetrating power. Also they do not produce a heating effect on the object to be sterilized. Ionizing radiations can be utilized for sterilizing catgut, dressing and surgical instruments.
ii) Ultraviolet rays: They have a poor penetrating power. Also they take a long time to produce complete sterilization. Ultraviolet rays can be used for sterilizing hospitals and operation theaters.
5. Lime: It is used in the form of i) quick lime ii) milk of lime (which is an aqueous suspension). Lime is used for disinfecting feces and also for white washing.
6. Bleaching powder: It is used for disinfecting feces, urine, sputum, pus and water.
7. Potassium permanganate: It is used in the form of a weak solution. It disinfects contaminated vegetables and fruits.
8. Formalin: It is used in the form of a liquid or gas. It is used for disinfecting rooms, walls and furniture.
9. Phenol: Pure phenol occurs in the form of crystals. It is highly corrosive. However, crude phenol (which contains some cresol) can be used for disinfecting feces.
Disinfection of feces and urine
Feces and urine should be collected in impervious vessels (Feces should be broken with a stick before disinfection). An equal volume of quick lime or freshly prepared milk of lime is added. It is mixed well and left for 2 hours. Later, the whole thing is emptied into water closet or buried in the ground.
Disinfection of sputum
Sputum may be received in paper handkerchief or gauze and destroyed by burning. If the amount is more, it is disinfected by boiling or autoclaving. Alternatively, the patient may be asked to spit in a sputum cup filled with 5 per cent cresol. When the cup is full, it is allowed to stand for an hour. Then the contents are emptied.
Disinfection of room
Usually, thorough cleaning, airing and exposure to sunlight is enough. For disinfection, floors and walls ae mopped or sprayed with chlorinated lime or formaldehyde solution. Rarely fumigation can be done with formaldehyde.
Disinfection of linen
Linen soiled with excreta should be first soaked in 10 per cent formalin or 5 per cent phenol. Such linen and other linen are then boiled or autoclaved.
Disinfection of instruments
Blunt instruments can be disinfected by boiling or autoclaving. Sharp instruments like knives and scissors are treated with chemical disinfectants like Lysol or carbolic acid. Syringes can be autoclaved or boiled in plain water.
Disinfection of dead bodies: It is done by embalming which is the most effective method. The solution used for embalming has the following composition:
Formalin 40 % – 2 to 3 liters.
Glycerin – 3 liters.
Alcohol – 1 liter.
Common salt – 1 kg.
Carbolic acid – 60 ml.
It is made up to 10 liters with water. 10 liters of this solution is used for one dead body. This solution is pumped through femoral artery. Dead bodies disinfected by this method resist decomposition and are stable even beyond 20 years.