Disinfection Methods: Chemical, Physical, and Biological Approaches
Disinfection Methods
1. Chemical Processes: These are used for disinfection and can act in two ways:
Microbiostatic Action: Impedes the growth and proliferation of microorganisms.
Microbicidal Action: Destroys microorganisms in the environment, killing them.
These compounds can act as disinfectants or antiseptics.
– Antiseptics: Chemicals that kill pathogenic microbes, but not all, and can be tolerated on the surface of living organisms. Examples include ethyl alcohol, hydrogen peroxide, iodine solutions, Mercurochrome, antibiotics, etc. The term antiseptic generally refers to substances applied to the body.
– Disinfectants: Compounds whose action on the organism is more energetic than antiseptics, even leading to sterilization. They are irritating and toxic to humans, so they are only used on objects. The word disinfectant commonly designates substances applied on surfaces, utensils, etc.
Examples include bleach disinfectant, phenol, formaldehyde, concentrated oxygen, etc.
Some disinfectants act as antiseptics when less concentrated and can be applied to the body in this case.
– Chemotherapeutic Chemicals: These are substances that act on bacteria by killing or paralyzing their action, thus facilitating the action of the body’s natural defenses, but they have the particularity of avoiding harm to the individual under treatment. They are effectively used to fight microbial diseases in humans and animals. Sulfonamides are among the best known.
2. Physical Processes: Organisms can be attacked by physical agents, including sterilization.
– Sterilization can be defined as an operation to destroy all microorganisms present in a given material. The most important procedures are dry heat or moist heat.
Heat affects proteins and nucleic acids necessary for the life of microorganisms. It is applied in different ways:
a) Dry Heat: The destruction of microorganisms can be achieved by direct flames or in an oven called a Pasteur kiln, where the temperature is raised to 180°C and maintained for about two hours. Materials that do not alter at very high temperatures, such as glass or metal objects, are used.
b) Moist Heat: Used to sterilize materials that are altered or burn at temperatures achieved in kilns, such as culture media, Pasteur cloth, Godon cloth, etc.
It involves the autoclave, an apparatus containing water that evaporates with increasing temperature, filling the space where the materials to be sterilized are located with an atmosphere of water vapor. This water vapor, increasing the temperature above 100°C, being hermetically sealed, reaches a pressure of one atmosphere (equivalent to 120°C). The combined action of temperature and humidity kills bacteria and other microorganisms within 20 minutes.
When using steam at temperatures below 100°C, it is called pasteurization. This method does not destroy the resistant forms of microorganisms, but it does eliminate a significant number of infectious agents.
– Radiations: Microbial destruction occurs when radioactive ions affect their molecules, such as DNA. The most used are gamma rays, especially ultraviolet (UV).
Ultraviolet radiation has limited penetration and only acts on places that are perpendicular to the impact, therefore only acting in small places such as theaters and on smooth surfaces.
– Filtration: To eliminate microorganisms from certain chemicals, very small pore filters are used in which the microbes are retained. However, viruses are not filterable and their minimum size allows them to pass through the filters without difficulty.
3. Biological Treatments: These are substances produced by microorganisms such as molds, among others, that in very small amounts inhibit the development of many microbial pathogens. They are currently obtained artificially by the pharmaceutical industry. They also have the feature of not being harmful to individuals who are administered, making them one of the most commonly used drugs to combat infectious diseases. They are known as antibiotics.
The first known antibiotic was penicillin, discovered by Fleming in 1929. It had a great impact since it was applied to treat bacterial infections in humans and banished antibiotics, the mortality caused by infectious diseases.
However, the marketing of these products has led to their abuse, which leads to the selection of bacterial populations, resulting in new strains resistant to antibiotics. This is also, in our time, the resurgence of infectious diseases that no longer respond to treatment with certain antibiotics.
The pharmaceutical industry produces a large scale using microorganisms, and at present, there are a large number of them, among which are worth mentioning terramycin, streptomycin, baritricina, tetracyclines, cephalosporins, etc.
Viruses, lacking their own metabolism, are unaffected by the action of antibiotics.
An antibiogram is an analytical test that involves determining the appropriate antibiotic for each bacteria. It is performed by placing small disks impregnated with various antibiotics (at different concentrations) on a culture plate infected by bacteria. Bacteriostatic or bactericidal action of different antibiotics can be tested by measuring the protective halo surrounding each disc. The antibiotic present with a greater halo is best suited to combat the infection.
Biotechnology is one of the most innovative and promising fields of microbiology and contemplates the use of microorganisms in large-scale industrial processes.
industrial processes.