Control of micro-organisms means reduction in the number and/or activity of micro-organisms. The main objectives behind the microbial control include :
1. Prevention of occurrence and transmission of diseases and infection.
2. Prevention of cotamination or growth of undesirable organisms, especially during microbiological studies, fermentation processes, analytical methods or processes involving use of microorganisms.
3. Prevention and control of deterioration of materials or spoilage foods of by micro-organisms.
Principles of microbial control :
Control of micro-organisms can be achieved by meeting with any of the following criteria.
1. Killing of micro-organisms.
2. Removal of micro-organisms.
3. Inhibition of the growth and activities of micro-organisms.
The agents capable of killing the micro-organisms or Inhibiting their growth and activity are called antimicrobial agents.
General mechanisms of antimicrobial action
Viability of the organisms and their ability to grow depends on the normal structure and function of many vital components of cell, especially cell wall, cell membrane, nucleie acids, proteins and activity of several enzymes performing metabolic pathways.
The antimicrobial agent effect one or many of these cellular components and influencing viability of organisms. The mode of action of various antimicrobial agents can be generalized as under.
• Damage to cell wall and/or inhibition of cell wall synthesis -
Bacterial cell wall is a rigid structure and protects the cell from lysis due to osmotic changes in the environment. Therefore, damage to cell wall, its lysis or inhibition of cell wall synthesis cause lysis of cells and kills bacteria.• Interference of cell membrane function -
Cell membrane of bacteria is selectively permeable. It controls exit and entry of molecules from and into the cell. Thereby, It controls cytoplasmic concentration. In addition, it possesses various important enzymes, essential for vitality of cell. Agents, able to damage cell membrane, may alter its selective permeability or interfere with its function and hence affect the cell. usually causing Its death.• Interference with protein -
Structure, function and synthesis Proteins are important macromolecules of cell. Many of them are essential for formation of cell structures. Others are essential for cell activity. Hence the agents. which modify physiochemical structure of proteins, change their conformation or inhibit protein synthesis are able to inhibit the growth or kill the organisms.• Effect on cellular nucleic acids -
Both the types of nucleic acids, RNA and DNA, play a key role in vitality of cells. RNA participates in protein synthesis. DNA acts as genetic material. Hence alterations in structure of the nucleic acids or inhibition of their synthesis inhibit the organisms.• Inhibition of enzyme action -
Enzymes are responsible for all metabolic processes going on within the cell. Therefore, agents capable of Interfering with or inhibiting the activity of enzymes Interfere with metabolism and hence the growth.Terms associated with the control of micro-organisms
Following terms are commonly used to describe processes and agents used for controlling micro-organisms.
Sterilization :
The process of destroying or removal of all forms of living organisms from the materials is called sterilization. Such objects, free from micro-organisms are called sterile.The process is employed to remove all the contaminating. unwanted organisms from the materials which may affect cultivation. study or application of micro-organisms. This method is mainly used in fermentation industries and laboratory for sterilize culture media.
Pasteurization :
The process, in which only harmful, pathogenic organisms are aimed at removal, without affecting quality of material is commonly known as pasteurization.This process is normally employed for treatment of milk. food and beverages (bear and wine) to destroy pathogens or harmful contaminants, The term is named so after the inventor of the process, Louis Pasteur.
Disinfection and Disinfectant :
Disinfection is the process of destroying infectious pathogenic mlcroorganisms, The agent used for the purpose Is called disinfectant.These agents are usually the chemicals which destroy vegetative growing formsol pathogens. but not necessarily the spores. The term is usually applied when the treatment is applied to Inanimate objects.
Antisepsis and antiseptic :
The process that prevents sepsis i.e. growth or activity microorganisms is called antisepsis. The agent used for the purpose Is called antiseptic.These are also usually the chemical agents that act by killing the micro-organisms or inhibiting their growth. Usually term is used, when the agent is applied to the body.
Sanitization and sanitizer :
The process in which the microbial number in the environment or materials is reduced to a safe level as Judged by public health standards is called sanitization.Agents used to achieve sanitization are called sanitizer. Reduction in the number of microorganisms to a safer low level reduces chances of infections and hence helps in maintaining general public health parameters.
These agent may be physical or chemical and are applied usually to Inanimate objects such as utensils, vessels and equipments used in dairy and food Industries, restaurants etc. as well as environment such as air and water.
Germicide :
An agent that is used to kill growing organisms but not necessarily spores is called germicide. Thus, the term is synonymous with disinfectant. But, germicides are used commonly to destroy but all forms of micro-organisms (germs) not only the Infectious organisms.Microbicide :
An agent able to kill micro-organisms is called microbicide. They can be categorized in to different types on the basis of the group of micro-organisms they kill.Accordingly they can be grouped as bactericide, viricide, fungicide, algicide, sporicide etc. These agents are usually chemicals.
