Micro organisms can be killed, removed or inhibited by various physical agents, physical processes and chemical agents. It should be realised that physical factors probably exert their influence upon the cell by influencing chemical changes in the environment or within the cell. A number of physical and chemical agents are available. They act in many different ways and each has its own limited practical application.
In the first place it is important to understand certain modern terms used to describe these agents and their results.
1) Sterilization:
Sterilisation is a process of destroying all forms of life by physical or chemical agents. It includes removal of organisms by means of centrifugation or filtration. It refers to complete absence or destruction of micro organisms and should not be used in a relative sense. An object or substance is sterile or non sterile. It can never be semi sterile or almost sterile.
2) Disinfectant:
Disinfection is accomplished by chemical agents called disinfectants. Disinfection means killing or removal of organisms capable causing infection. It kill the vegetative cells, but not heat resistant spores. A disinfectant is normally applied to inanimate objects such as floors, utensils, buildings, equipments, laundry etc.
3)Antiseptic :
The term antiseptic is used to designate any substances which would prevent sepsis, either by killing micro organisms or by inhibiting their growth and activity. An antiseptic can be applied to body tissues without causing injury to them while, most disinfectants are destructive to tissues of body
4)Sanitizer :
An agent that reduces the microbial population to safe levels as judged by public health requirement. It’s a chemical agent that kills 99.9 percent of growing bacteria. Sanitiser are commonly applied to inanimate objects and are generally employed in the daily care of equipment and utensils in dairies, food plant and for glasses , dishes and utensils in restaurants.
5) Bactericides :
An agent that kills bacteria. similarly -fungicide, virucide and sporicide refers to agents that kill fungi, viruses and spores respectively
6) bacteriostasis:
A condition in which the growth of bacteria is prevented. In presence of bacteriostatic agent metabolism of bacteria is inhibited. The bacteria die over a period of time without significant multiplication. However on removal of bacteriostatic agent and in the presence of favorable environmental condition results in growth in bacteria