The difference between disinfection and sterilization: everything you need to know

In hospitals and laboratories, disinfection, sterilization and cleaning are part of the daily routine. Although these terms are often mentioned together, the differences between the actual procedures are great. Here we have compiled a detailed list of the exact differences between disinfection and sterilization, which definitions are relevant in each case, and which procedures, methods and areas of application are differentiated.

Overview: Difference between disinfection and sterilization and cleaning.

Even an initial superficial examination reveals significant differences between the processes of disinfection, sterilization and cleaning. These concern not only the work areas in which the methods are used, but also the procedures themselves.

Already here, the cleaning falls behind the other two. This is because cleaning is much less effectiveand microorganisms cannot be killed with it. Germ reduction is also only 50-80 percent. Therefore, this step is rather used as a preparatory step before disinfection or sterilization. The main differences there are the following:

• Disinfection allows germ reduction, while sterilization provides complete sterility.
• While sterilization can be performed by steam, hot air or a chemical process, disinfection is primarily performed chemically.
• Besides bacteria, disinfection also kills some viruses. However, sterilization kills all microorganisms and even stubborn spores, which is why it is considered much more aggressive.
• The main areas of application for disinfection are human skin, surfaces and instruments. In the case of sterilization, it is primarily medical instruments and laboratory components (such as scalpels, syringes or culture media).

Definition of disinfection: rendering pathogens harmless

When disinfection is mentioned, it is a process designed toreduce disease-causing microorganisms. Thus, the goal is to ensure that disinfected surfaces, objects or materials no longer pose a risk of infection. This also applies to the skin – for example, before medical procedures. By the way, there are also different types of disinfectants for this purpose.

The germ reduction during disinfection is between 84 % and 99.9 %. The germs are both reduced in number and inactivated so that they can no longer cause infections. This is one of the reasons why this procedure is mandatory in hospitals and medical facilities as well as in the food industry.

Procedure

In order to achieve the greatest possible effect during disinfection, various procedures are used. Here, too, there is a difference between disinfection and sterilization, as these processes are much less standardized. For disinfection there are mainly these methods:

• Spraying: When spraying, the disinfected surface is completely wetted with the disinfectant, which should be done with a certain distance between the spray head and the surface. However, the distance should also not be too great – because then there will be excessive pollution of the breathing air in the room. The spraying method is therefore used more for small areas.

• Wiping:Wiping also involves mechanical cleaning, as dirt particles are also removed – which is one of the reasons why this procedure is preferred to spraying. The surface must be completely wetted and dried. To prevent the spread of germs, the wipe must be highly absorbent.

• Immersion bath: If objects are to be completely covered, the immersion bath is the final option. This is made with cold water and covered to prevent the disinfectant from evaporating. A daily renewal is mandatory.

Intended use

Not only different procedures, but alsodifferent purposes can be mentioned for disinfection. The following uses in particular represent the core area of this process:

• Skin and mucous membrane disinfection: If the skin has to be injured in the course of an intervention (think of a blood sample, for example), pathogens lying on the skin must not be allowed to enter the organism. Therefore, thoroughly disinfected beforehand. This is followed by a short exposure time of 15 to 30 seconds to ensure the death of harmful microorganisms. Mucosal disinfection, on the other hand, is performed before bladder catheterizations.

• Hand disinfection: Hand disinfection is also intended to reduce possible pathogens on the skin and render them harmless. However, the focus here is on the transmission factor: viruses and bacteria, for example, should not be carried around on the hands in order to be transmitted to other people.

• Disinfection of objects and instruments: The so-called “wet disposal”, by which the disinfection of objects and instruments is meant, is also intended to counteract the spread of germs. Medical instruments, for example, are placed in an immersion bath immediately after use.

• Disinfection of surfaces: Disinfection of surfaces should be carried out not only at regular intervals, but also when there is visible contamination with infectious material (think, for example, of sputum or urine). It is particularly elementary in areas with a high risk of infection, which includes surfaces in a hospital or laboratory.

Ingredients and active ingredient classes

Different active ingredients are used for different areas of application – not least because of this, various ingredients are also found in disinfectants. The classes of active ingredients can be divided as follows for chemical disinfection:

Methods

Not all disinfection is the same - so it is also possible to distinguishthree methods by which such disinfection can be carried out. Particularly in the private sector and in the usual hospital routine, a chemical approach is used, although this can also be supplemented by a physical or chemothermal variant:

• Physical approach: Here, the safe application and good environmental compatibility are definitely an advantage. The physical approach is either by radiation (with UV rays) or by dry or moist heat. The jets are used primarily to disinfect the air in the room, while heat-resistant materials are the focus for dry heat. For pillows and mattresses, the application of moist heat is optimal. Boiling can also be counted as physical disinfection.

• Chemical procedure:Chemical disinfection uses special disinfectants to target pathogenic agents. These must comply with the guidelines of the DGHM (German Society for Hygiene and Microbiology) and act in various ways, e.g. enzyme inhibition, destruction of cell protein or disruption of the cell wall function of the microorganisms.

• Chemothermal procedure:Finally, chemothermal disinfection combines both procedures, as both chemical agents and elevated temperatures of 50 °C to 60 °C are used here. However, mechanical chemothermal processes are only used if, for example, there is a material incompatibility for a purely chemical process (such as in the reprocessing of endoscopes).

Procedure

The methods and procedures already show that several procedures can be used. These are identified by impact areas from category A to Dto indicate effectiveness. Unlike sterilization, however, it is not possible to achieve 100% sterility.

While area A procedures kill vegetative bacteria, fungi, fungal spores and mycobacteria, according to the Robert Koch Institute (RKI), area B also inactivates viruses. C also kills anthrax spores, and D adds spores of gas edema and tetanus pathogens. The procedures are divided as follows:

Definition sterilization: germ-free and pure

In order to be able to explain the difference between disinfection and sterilization, the specifics of the second procedure must of course also be addressed. In sterilization, both methods and procedures are distinguished from each other, although they are less extensive than in disinfection.

According to DIN EN 556, sterilization is defined by the fact that this process results in 100 percent sterility by killing and inactivating microorganisms of all kinds (such as bacteria, viruses, prions and spores). This applies to all stages of development, so that even extremely stubborn representatives are killed. Generally, the number of all microorganisms still alive is reduced to ^{≤ 10-6}per unit of sterilized material. Therefore, sterilization is also called sterilization.

Methods

In contrast to disinfection, sterilization is only differentiated between physical and chemical sterilization. This is simply because the other previously mentioned methods could not achieve complete sterility.

• Physical sterilization: Physical sterilization can be divided into hot air sterilization, steam sterilization and radiation sterilization and is characterized by the fact that heat leads to irreversible destruction of microorganisms. In these, the protein of the cells decomposes so that they become harmless.

• Chemical sterilization:Chemical sterilization is a cold sterilization process performed with the aid of gas. The toxicity of these gases causes all microorganisms to denature and die.

Procedure

Different processes are used not only for disinfection but also for sterilization - here, too, there is a difference between disinfection and sterilization. These are primarily based on the material and the thermostabilityof those items that need to be sterilized. The most common procedures include these in particular:

• Sterilization by steam:Steam sterilization involves the application of moist heat, which is introduced into a so-called steam sterilizer or autoclave at approximately 134 °C for 5 minutes or also at 121 °C for 20 minutes. An overpressure of 2-3 bar prevails there, so that a water vapor-saturated atmosphere is created. Sterilization by steam, i.e. autoclaving, is mainly used for textiles, instruments, heat-resistant plastics and rubber.

• Hot air sterilization:Hot air sterilization belongs to the dry heat category and usually takes place at around 180 °C for about 30 minutes. The device used is a so-called hot air sterilizer, which allows hot air to completely flow around the item to be sterilized. However, due to the large amount of heat generated, only heat-resistant objects can be considered, which include metal, glass and anhydrous liquids.

Sterilization by UV, X-ray, beta or gamma rays:Radiation sterilization used exclusively in an industrial setting, as it is equal parts time-consuming and expensive. The ionizing radiation used for this destroys the nucleic acids in the cells of the microorganisms. The advantage of this is that the material is not exposed to heat, which is why dressings and catheters, for example, can be sterilized using this method.

• Sterilization by plasma:Plasma sterilization is also suitable for thermolabile items such as plastic syringes and infusion sets. In this process, plasma discharges are induced by high-frequency waves and microwaves, which is why even problematic prions can be killed.

• Sterilization by gas:Finally, gas sterilization is a possibility, which is primarily carried out with ethylene oxide, ozone or formaldehyde. In this process, the sterile material is aerated with the toxic gas for between 30 minutes and 6 hours, so that the protein of the microorganisms is irreversibly altered.

Difference between disinfection & sterilization: areas of application

If we look at the difference between disinfection and sterilization, we can say that several areas are involved at once. These range from the different approaches and methods to the different areas of application. But at the top of the list, of course, is the effectiveness, which is much higher in a sterilization process. If we summarize all these aspects with regard to the possible fields of work, the following overview results:

The difference between disinfection and sterilization is essential

Although the difference between disinfection and sterilization is primarily due to the actual killing of germs, it is also determined by the different procedures, methods and areas of application. Theingredients of disinfectantsare also important in the differentiation. Depending on the materials or objects involved and the environment in which germ reduction is carried out, disinfection or sterilization is more appropriate.

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