Disinfection: Types and Physical Methods
The term originates from the French des (removal) and the Latin infectio (infection). Unlike sterilization, disinfection destroys only the bulk of pathogenic microorganisms, whereas bacterial spores and particularly resistant forms may survive.
Depending on the epidemiological situation, three types of disinfection are distinguished:
- Prophylactic — performed regularly to prevent the emergence of diseases even if no patients are nearby.
- Current (focal) — carried out at the bedside of an infected patient to reduce the concentration of pathogens in the environment.
- Terminal — necessary for complete cleaning of the focus after the source of infection has been eliminated (e.g., after hospitalization, recovery, or death).
For decontamination, thermal methods are widely used: boiling, treatment with hot steam in washing machines, and calcination (dry heat). For liquid food products, pasteurization is used—short-term heating at various temperature regimes (from 61.5 °C to 150 °C). In medical and industrial premises, bactericidal lamps are actively used. They generate ultraviolet radiation that effectively cleanses the air and working surfaces.
Chemical Disinfection
If an object cannot tolerate high temperatures (heat-labile instruments, skin, room surfaces, water), chemical substances are used. They dissolve lipid cell membranes or destroy microbial proteins and nucleic acids.
According to the mechanism of microbial cell damage, four groups of disinfectants are distinguished:
- Destructive — cause dissolution (lysis) or denaturation of proteins.
- Oxidizing — act through active oxygen or halogens (hydrogen peroxide, potassium permanganate).
- Membrane-attacking — disrupt the permeability of cell walls (these include detergents).
- Antienzymatic — block the internal enzyme systems of bacteria (heavy metal salts, 8-hydroxyquinolines).
For volumetric decontamination of equipment and apparatus, gas mixtures can be used (e.g., ethylene oxide with methyl bromide).
Asepsis: Prevention of Infection
Asepsis is understood as a system of measures that prevent microorganisms from penetrating (contaminating) a wound, patient tissues, or medical devices. This is critically important in surgery, microbiological production, and the food industry.
Asepsis is implemented through a set of barriers:
- Maintenance of sterility — the use of exclusively sterile linen, instruments, and dressings.
- Disinfection measures — thorough processing of personnel hands and the surgical field.
- Barrier protection — wearing masks, gloves, and specialized clothing.
- Organizational solutions — separation of rooms (compartmentalization), installation of specialized ventilation systems.
Antisepsis: Combating in the Focus
Antisepsis is a set of therapeutic actions aimed at destroying microbes that have already penetrated the body, wound, or pathological focus.
Depending on the approach, antisepsis is divided into four types:
- Mechanical — physical removal of dead (necrotic) tissues, infected areas, and foreign bodies from the wound.
- Physical — ensuring the outflow of infected contents using drains, tampons, and hygroscopic dressings.
- Biological — the use of enzymes to break down non-viable tissues, as well as the use of specific agents (antibiotics, bacteriophages) for the direct destruction of the pathogen.
- Chemical — the use of antimicrobial drugs (antiseptics) to drastically reduce the microbial population. This includes halogens (iodine and chlorine preparations), oxidizers, acids and alkalis, alcohols, dyes (e.g., brilliant green), and detergents (chlorhexidine).
Briefly: answers to topical questions
What are the modes of steam sterilization under pressure?
Modes of steam sterilization under pressure (autoclaving) vary depending on pressure, temperature, and exposure time. The following parameters are used in medical practice:
- Gentle mode — 120 °C at a pressure of 1.1 atm for 45 minutes.
- Standard mode — 121 °C at 2 atm for 15–20 minutes (ensures the death of spores).
- Rigid mode — 130 °C at 2 atm for 20 minutes (for surgical linen, the temperature may be 132.9 °C).
- Short-term high-temperature mode — 134 °C for 3–5 minutes.
- Prion inactivation modes — 121 °C for 4 hours or 134 °C for 30 minutes.
Which specific preparations belong to halogen-containing antiseptics?
Halogen-containing antiseptics include iodine and chlorine preparations.
- Iodine preparations: 5% alcoholic iodine solution, Lugol's solution, iodoform, iodinol, iodopyron, iodonate.
- Chlorine preparations: chloramines, including chloramine B, and chlorites.
A 5% alcoholic iodine solution is used for treating the skin, Lugol's solution for mucous membranes, iodopyron for local treatment of infected wounds and burns, as well as for treating the surgeon's hands and the surgical field. Chloramine B is used for disinfecting premises, care items, and interior furnishings; it is not used for washing wounds.
Remembering the difference between the terms is simple: Asepsis is the 'shield' (preventing microbes from entering before contact), and Antisepsis is the 'sword' (destroying microbes when they are already in the wound).
Class and exam questions
What is the main difference between disinfection and sterilization?
During disinfection, the majority of pathogenic microbes are killed, but bacterial spores and some resistant microorganisms may survive. Sterilization, on the other hand, implies the complete destruction of all forms of life.
What are the pasteurization modes?
There are three main regimes: low-temperature (61.5 °C for 30 minutes or 71 °C for 15 seconds), high-temperature (80–85 °C for several seconds), and ultra-high-temperature (130–150 °C).
Why are preservatives used in pharmaceuticals?
They are added to dosage forms to prevent the proliferation of microbes there. Guanidine derivatives, organic acids, aldehydes, and mercury compounds can be used as preservatives.
What else to study on this topic
- Classification of chemical antiseptics by structural groups (halogens, alcohols, detergents)
- Use of heavy metals and dyes in surgical practice
- Features of mechanical and physical wound antisepsis
- Mechanisms of action of chemical disinfectants at the cellular level
- Organizational and planning measures in the asepsis system of medical institutions
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