Introduction to disinfectants.

Introduction:

The word control refers to the reduction in number or activity of total microorganisms. There are various methods of control of microorganisms. There are various physical agents, chemical agents, and physical process to reduce , kill or inhibit the growth of microorganisms.Microorganisms are to be controlled due to following reasons;

• to prevent transmission of disease and infection.
• To prevent contamination and growth of unwanted microorganisms.
• To prevent the destruction and spoilage of material that are caused by microorganisms.

Some methods for the control of microorganisms are as follows:

1. Sterilization: The process of complete removal of all forms of microorganisms from an object is called sterilization. It refers to complete absence or overall destruction of microorganisms. The term sterile means the complete absence of microorganisms.
2. Antimicrobial agent; Those chemical or physical agents that regulate the growth and metabolism of microorganisms are called antimicrobial agents. The term anti bacterial , antifungal and antiviral refers to the agents that interact with the growth and metabolism of bacteria, fungi and virus respectively.
3. Disinfectant; Those chemical agents that kill the growing form of microorganisms but not necessarily the spore of disease-producing microorganisms is called disinfectants. The term disinfectant is used for inanimate objects as it is the process of destroying infectious agents.
4. Antiseptic: Chemical agents that prevent the growth and action of microorganisms either by destroying microorganisms or by inhibiting their growth and metabolism are known as antiseptics. it refers to the process of preventing growth or action of microorganisms on the body so this term is applied to the body.
5. Sanitizer: Those chemical agents that reduce the population of microorganisms to the safe level as judged by public health requirement are known as the sanitizer. They are also commonly applied to inanimate objects.
6. Germicides; Those agents that kill the growing form of microorganisms but not necessarily the spore or germ of microorganisms is called germicide.
7. Bactericide:It s used to kill the bacteria. Those agents that are used to kill the bacteria are known as the bactericide. Similarly fungicide, virucide, and provide are used to kill fungi, virus, and spores respectively.
8. Microbistatic: Those chemical agents that have the ability to inhibit the growth of the microorganism is called microbiostatic. Similarly bacteriostatic, fungistatic are the chemical that is used to inhibit the growth of bacteria and fungi respectively.

Principle of sterilization:

When the microorganisms are subjected to appropriate antimicrobial agent for sufficient time and at optimum condition,killing of microorganisms occur due to the irreversible loss of function and activity of microorganisms. Various antimicrobial agents kill the microorganisms by various mechanisms such as:

• Damage to the cell wall or inhibition of cell wall synthesis.
• Alteration of the permeability of the cytoplasmic membrane.
• Inhibition of enzyme action,
• inhibition of protein or nucleic acid synthesis.

All the microorganisms cannot be killed by same microbial agents at the same condition. During the sterilization of various materials, the agents and condition applied should kill all forms of microorganisms but it should not destroy the quality of material Hence sometimes different agents are used to sterilizing the different material although having the similar organisms.

Factors affecting action of anti microbial agents:

Many factors are responsible to influence the action of antimicrobial agents . All materials cannot be sterilized by the same antimicrobial agent under all conditions maintained. Some important factors that influence the rate of killing microbial agents are as follows:

1. Environment; the Physical or chemical property of culture medium hs great effect on the rate of killing. eg; effectiveness of heat is much greater in acid than in the alkaline environment . Nature of material also affects the penetration of the agent. Similarly,high content of organic matter decreases the efficiency of antimicrobial agents by inactive or by protecting microorganisms from it.
2. Nature of microorganisms: Not all types of organisms are killed by same agent and condition. Some organisms are more resistant while some are less. Spores are more resistant than vegetative cells. Spores are most resistant to all types of microorganisms.
3. The physiological state of the cell; This determines the susceptibility of organisms to antimicrobial agents. eg, young , actively metabolizing cells are destroyed more easily than old, dormant cells by antimicrobial agents that kill by regulating metabolism.

Death of microorganisms:

It is the state of irreversible loss of reproducibility i.e the state of microorganisms in which it never undergoes reproduction and multiplication in any environment condition.

Mode of action of antimicrobial agents.

Antimicrobial agents either kill or inhibit the functions of microorganisms. Antiseptics, Antibiotics , Disinfectants are some examples of microbial agents The mode of action of antimicrobial agents is as follows.

• Cell wall synthesis inhibition.
• Cell membrane synthesis inhibition.
• Nucleic acid synthesis inhibition.
• Protein synthesis inhibition.
• Anti-metabolism (Sulfa Drugs).

References:

C.H.Collins. (1995). Microbiological Methods. Oxford Univ Press.

D.Greemwood, R. S. (2002). Medical Microbiology. London: Churchill Livingstone.

M.J.Pelezar. (1993). Microbiology. Tata McGraw hill.

M.T.Madigan, J. a. (1997). Biology of microorganisms. London: Prentice hall International Inc.

R.N.Atlas. (1984). Fundamentals and Applications. NewYork: MacMiHiam Publishing Co.