When disinfecting (sterilization), in addition to paying attention to the nature and characteristics of the disinfection method itself, it is also necessary to pay attention to the influence of the use method and external factors on the disinfection effect. Regardless of the toxic method used, the disinfection effect will be affected by many factors. The mastery and utilization of these factors can improve the disinfection effect, and vice versa will affect the disinfection effect or lead to disinfection failure. The main influencing factors are the following.
1. Disinfected dose
The disinfecting dose is the basic condition for killing microorganisms, which includes both disinfection intensity and time. The disinfection intensity refers to the temperature when it is thermally disinfected; when it is chemically disinfected, it refers to the concentration of the substance; when it is disinfected by ultraviolet rays, it refers to the intensity of ultraviolet radiation. In general, increasing the intensity of the disinfection treatment can increase the speed of disinfection (sterilization); while reducing the time of disinfection can also reduce the disinfection effect. Of course, if the disinfection intensity is reduced to a certain extent, even if the time is extended, the disinfection purpose is not achieved.
2. Species and quantity of microbial contamination
Different types of organisms have different effects on their disinfection. In addition, the amount of microorganisms also affects the disinfection effect, so the type and amount of microbial contamination should be considered before disinfection. In general, the stronger the resistance of microorganisms, the more serious the pollution, and the more difficult it is to disinfect.
3. Temperature effect
In addition to thermal disinfection relies entirely on temperature to kill microorganisms, various other disinfection methods are also affected by temperature changes. In general, the temperature is better as it is in physical disinfection or disinfectant. The extent of the effect of temperature changes on the disinfection effect often varies with the method of disinfection, the type of drug and the type of microorganism, and is generally expressed by the temperature coefficient.
4. Relative temperature
The influence of the relative humidity of the disinfection environment on the gas disinfection and fumigation disinfection is very obvious. If the temperature is too high or too low, the disinfection effect will be affected, and even the disinfection failure will be caused. The relative humidity of indoor air formaldehyde fumigation should be 80–90%, the relative humidity of small ethylene oxide disinfection treatment should be 40–60%, and the large disinfection (>0.15 cubic meters) should be 50%–80%. . In addition, the ultraviolet light has a strong bactericidal power below 60% relative humidity, and the sterilizing power is reduced by 30%-40% at 80%-90%, because the relative humidity increases to affect the penetration of the ultraviolet ray.
5. PH (pH)
Changes in pH can directly affect the effectiveness of certain sterilization methods. On the one hand, the effect of pH on the disinfectant itself reduces or increases the activity of the disinfectant; on the other hand, the effect of pH on the microorganisms. For example, when glutaraldehyde is raised from 3 to 8, the bactericidal effect is gradually enhanced; while in hypochlorite solution, when the pH is increased from 3 to 8, the bactericidal effect is gradually decreased; chlorhexidine and quaternary ammonium compounds The bactericidal effect is large in an alkaline environment.
6. Organic matter
Organic substances in the disinfection environment can often inhibit or reduce the sterilization ability of disinfection factors, especially the sterilization ability of chemical disinfectants. This is because on the one hand, the organic matter is surrounded by microorganisms, which protects the microorganisms and hinders the penetration of the disinfection factor. On the other hand, in the chemical disinfectant, the organic matter itself can also consume a part of the chemical disinfectant through the chemical reaction. Various disinfectants are affected by organic substances. For example, in the presence of organic substances, the bactericidal effect of chlorine-containing disinfectants is significantly reduced; the disinfection of quaternary ammonium salts, biguanides and peroxy compounds is also affected by organic matter. However, disinfectants such as ethylene oxide and glutaraldehyde are less affected by organic substances. If organic matter is present, the amount of disinfectant should be increased.
7. Antagonistic substance
For chemical disinfection methods, attention should be paid to the neutralization and interference of antagonistic substances. For example, the action of quaternary ammonium disinfectants can be neutralized by soap or anionic detergents; acidic or alkaline disinfectants can be neutralized by alkaline or acidic substances, reducing their disinfection.
When the item is sterilized, the bactericidal factor must act directly on the microorganism itself to sterilize. Different disinfection factors have different penetrating powers. For example, dry heat sterilization is inferior to wet heat penetration; formaldehyde steam sterilization is less penetrating than ethylene oxide; UV disinfection can only act on microorganisms on the surface of objects and shallow liquids, and a piece of paper can make it bactericidal. Reduce by more than 95%.