Sterilization (Microbiology)

Food Products

Since ancient times, partial sterilization of food was ensured by careful heat treatment during cooking. Heating food and water reduced the number of cases of infectious diseases, increasing life expectancy and working age. Preservation of food in sealed packaging was a logical continuation of this approach to preserving food.

Medicine

In medicine, sterilization refers to the microbial decontamination of inanimate objects. The principle of asepsis involves the exclusion of patient contact with surfaces contaminated with conditionally pathogenic or even pathogenic microbiota. For this purpose, scalpels , needles and other surgical instruments were sterilized. Sterilization also plays an important role in the production of parenteral drugs.

The heating of medical instruments was known even in Ancient Rome , but was forgotten in the Middle Ages , which led to a sharp increase in the number of complications and mortality after surgical operations .

• Thermal: steam and air (dry heat)
• Chemical: gas or chemical solutions (sterilants)
• Plasma (hydrogen peroxide plasma)
• Radiation sterilization - used in industrial version
• The method of membrane filters - is used to obtain a small number of sterile solutions, the quality of which can deteriorate sharply when other sterilization methods are used (bacteriophage, selective nutrient media, antibiotics) ^[1]

Thermal sterilization methods

Advantages of thermal sterilization methods:

• Reliability
• No need to remove sterilants from medical supplies
• The convenience of the staff
• Sterilization is carried out in packages, which allows to maintain sterility for a certain period of time.

Steam Sterilization

It is carried out by supplying saturated water vapor under pressure in steam sterilizers ( autoclaves ).

Steam pressure sterilization is considered the most effective method, since the higher the pressure, the higher the temperature of the steam sterilizing the material; the bactericidal properties of steam are higher than that of air; therefore, supersaturated steam is used for sterilization.

Steam sterilized products are made from textiles (linen, cotton , bandages , suture material), from rubber , glass , some polymeric materials, growth media, and medications .

For steam sterilization, the following packaging materials are used:

• Sterilization box ( Bix ) is simple. Shelf life 3 days after sterilization.
• Sterilization box ( Bix ) with a filter. Shelf life 20 days after sterilization.
• Kraft bags with staples. Shelf life - three days after sterilization.
• Sealing kraft bags. Shelf life - 50 days after sterilization.
• Fabric (calico - EXCEPT MARLEY). Shelf life - three days after sterilization.
• Combined packaging (transparent synthetic film + paper). Shelf life from 180 days to 720 days.

Tindalization

Tyndalization is used to sterilize solutions that are unstable to high temperature. It consists in repeated heating to a temperature of 70-100 ° C at intervals of 24 hours.

Chemical sterilization methods

They are used in the processing of devices, apparatuses, complex optical systems, large-sized products or products from titanium, polymer resins, rubbers.

For gas (cold) sterilization ^[2] , ethylene oxide or airtight containers with vapors of ethylene oxide, formaldehyde or specialized multicomponent systems are used.

For chemical sterilization with solutions, four main groups of substances are used:

• Acid + oxidizing agent (for example, “Pervomur”)
• Aldehyde (e.g. formalin )
• Detergent (e.g. chlorhexidine bigluconate )
• Halogen (e.g. Povidone-iodine )

Concentrations and sterilization times depend on the antiseptic or disinfectant used.

Ionization sterilization

• the radiation method or radiation sterilization with γ-rays is used in special installations for single-use industrial sterilization - polymer syringes, blood transfusion systems, Petri dishes, pipettes and other fragile and heat-sensitive products.
• For a number of years, ultraviolet (UV) (wavelength 253.7 nm) has been used in pharmaceutical technology for sterilization. The sources of UV radiation are mercury quartz lamps. Their powerful bacteriostatic effect is based on the coincidence of the emission spectrum of the lamp and the absorption spectrum of DNA of microorganisms, which may be the reason for their death during prolonged processing by radiation of quartz lamps. When UV is not powerful enough, the processes of light and dark repair are activated in the prokaryotic cell and the cell can recover. The method is used to sterilize supply and exhaust ventilation air, equipment in boxes, and also to sterilize distilled water. ^[3]

• Laminar Box
• Pasteurization

• WHO - Infection Control Guidelines for Transmissible Spongiform Encephalopathies . Retrieved Jul 10, 2010
• Ninemeier J. Central Service Technical Manual . - 6th. - International Association of Healthcare Central Service Materiel Management.
• Control of microbes
• Raju GK, Cooney CL. Media and air sterilization // Biotechnology, 2E, Vol. 3, Bioprocessing / Stephanopoulos G. - Weinheim: Wiley-VCH, 1993. - P. 157–84. - ISBN 3-527-28313-7 .
• Innovative Technologies for the Biofunctionalization and Terminal Sterilization of Medical Devices