Definition: Sterilization is the procedure of complete destruction (Killing) of all microorganisms present in a system. A product free from living microorganisms is called a “sterile product”.
Antiseptic: Antiseptic substance stops the growth of microorganisms by preventing their action without destroying them is called antiseptic.
Bactericide: The substance that kills bacteria is named as “Bactericide”.
Bacteriostatic: Bacteriostatic refers to a chemical that stops or slows bacterial growth.
Disinfection: A procedure that removes the infection likely by destroying microorganisms but not usually bacterial spores.
Germicide: A material, but not necessarily bacterial spores, that kills harmful germs.
Viricide: It is a substance that kills viruses.
Sterility: The absence of viable microorganism is called ‘sterility’ & preparation free from viable microorganisms are called ‘sterile’.
THERMAL RESISTANCE OF MICROORGANISMS
The microorganism show variable resistance to different Methods.
Thermal death time: It can be described as the length of time needed to eradicate a certain type of microbe under particular circumstances and at a specified temperature.
Death rate of microorganisms: There is no direct technique to determine when the sterility will be completed.
Decimal reduction time (D value): It is defined as the time in min. required to decrease the number of the viable organisms by 90%.
The order of death of microorganisms can be calculated from equation:
K = 1/t (log No.— log N)
Where,
K stands for constant which depends on organism, temperature and medium.
t is time of exposure in min.
No stands for number of organisms viable at the beginning of a time interval.
N=Number of organisms still viable at the end of the period.
K= 1/t
As, it is after 90% reduction in microorganism.
The D value, often known as the decimal reduction time, is defined as time t.
D= 1/K
METHODS OF STERILISATION
Physical Methods
Dry Heat Sterilization
Moist Heat Sterilization
Radiation Sterilization
Use Of Ultra Violet Rays
Ionising radiation
Chemical Methods:
Sterilization by heating with bactericide.
Gaseous Sterilization.
Mechanical Methods: It includes the filtration of parenteral preparation through the following bacteria proof filters:
1. Ceramic filters
2. Seitz filter
3. Sintered glass filters
4. Sintered metal filters
5. Membrane filters
Credit@researchgate.net
Reference:
Sterilization of hydrogels for biomedical applications: A review: STERILIZATION OF HYDROGELS