The efficacy categories of disinfectants: What you need to know

Illustration of a hand with an outstretched thumb.

From limited virucidal to sporicidal – disinfectants are available for all different efficacy spectra. What are these? Do I need a different disinfectant depending on the situation? How do I find the right product? We explain the different efficacy spectra and what this means for both the healthcare sector and the private sphere.

Bacteria on the door handle, molds in the changing room or viruses on the lift button – infectious pathogens are all around. Especially in winter, we are particularly exposed to potential pathogens like flu viruses. It’s reassuring that you can use disinfectants to help protect yourself against infection. However, when looking at products such as Sterillium®, laypersons are quickly overwhelmed by the many technical terms. Very few people know the meaning of words like yeasticidal, mycobactericidal, or virucidal. Fortunately, the topic is not as complicated as it first seems.

Classifying disinfectants

One of the most important criteria for classifying a disinfectant is the type of pathogen it is intended to combat. No product effectively eliminates all conceivable germs – from spores to bacteria [1]. The renowned Robert Koch Institute (RKI) in Germany has therefore developed the following categories of disinfectants [2]:

A: Disinfectants suitable for killing vegetative bacteria, including mycobacteria, and fungi, including fungal spores.

B: Disinfectants suitable for inactivating viruses.

C: Disinfectants suitable for killing spores of the anthrax-causing pathogen.

In other words, we distinguish between disinfectants that primarily combat fungi, bacteria, viruses, or other pathogens. Within these superordinate categories, however, we make further distinctions, which brings us to the spectrum of efficacy found on the labels of disinfectants such as Sterillium®.

Illustration of germ transmission when shaking hands. — Disinfectants are classified according to the pathogens they combat.

"Fungicide" and "bactericide": Controlling fungi and bacteria

Let's start with the differences between fungi and bacteria. In the case of the former, the term "fungicidal" is particularly important. It means that the disinfectant is effective against all fungi, fungal spores and yeasts. This includes, for example, the well-known moulds. If a product is labelled "yeasticidal", it is only effective against yeasts, such as the Candida albicans strain.

A "bactericidal" disinfectant kills bacteria, including all bacteria except the so-called mycobacteria. Mycobacteria are a genus of mostly rod-shaped bacteria, including, for example, leprosy or tuberculosis pathogens. The tuberculosis bacterium therefore has its own category - "tuberculocidal". However, there is also a superordinate label "mycobactericidal", which includes all mycobacteria including the tuberculosis strain.

And there is another special feature within category A: Contrary to what its name suggests, disinfectants with a "sporicidal" spectrum of action do not act against fungal spores, but against bacteria spores. This applies, for example, to bacteria such as Clostridioides difficile, which can trigger gastrointestinal inflammation with diarrhoea and are transmitted via a smear infection [3].

Closeup of bacteria in a Petri dish. — Disinfectants labelled "bactericidal" are effective against most bacteria.

Enveloped vs. non-enveloped: Combating viruses

Category B (viruses) also contains different efficacy spectra. This is mainly due to the difference between enveloped and non-enveloped viruses. Even if it sounds illogical, enveloped viruses are actually easier to combat. Although the lipid layer of enveloped viruses gives them a certain stability against environmental influences, this envelope is also their greatest weakness, as it can easily be destroyed by alcohol-based disinfectants. Even if the inside of the virus remains intact, breaking the lipid layer inactivates the pathogen. Non-enveloped viruses differ in that regard. Their central capsid is significantly more resistant to physical and chemical processes and therefore not as easy to combat.

Analogous to these differences in terms of sensitivity, there are three different efficacy spectra: While a disinfectant with the label "virucidal activity against enveloped viruses" is sufficient for enveloped viruses such as influenza and coronaviruses, less sensitive non-enveloped viruses require the "virucidal" spectrum of efficacy. This includes, for example, the enterovirus or the hepatitis A virus. Exceptions among the non-enveloped viruses are noro-, adeno-, and rotaviruses, as they are easier to inactivate than other members of the group of non-enveloped viruses. The spectrum labelled "limited spectrum virucidal activity" also works on this virus type.

Good to know: Many disinfectants combine several efficacy categories, which protects users against many pathogens. The classic Sterillium®, for example, is bactericidal, yeasticidal, mycobactericidal, tuberculocidal, and provides the label “virucidal activity against enveloped viruses”.

Illustration of viruses. — Non-enveloped viruses are significantly more resilient than enveloped viruses.

How are the efficacy categories determined?

Various methods are used to test a disinfectant’s spectrum of efficacy. One of the most common is the practical, or in vitro test, in which a disinfectant is tested in a test tube to see how it reacts to the corresponding pathogens with the addition of organic matter such as blood or protein. For each spectrum of efficacy, there are specifically defined test pathogens. In the case of “limited spectrum virucidal activity”, these are the adenovirus and the murine norovirus.

After a precisely defined period of time, one millilitre of the mixture of organic matter, disinfectant, and the test pathogen is removed from the test tube for further analysis. Laboratories use this procedure to determine whether the disinfectant can fight the test viruses or not. The respective disinfectant must inactivate a certain number of pathogens to be effective on a certain spectrum of efficacy.

A laboratory worker examines a sample. — The in vitro test tests how well disinfectants fight certain pathogens.

How do I find the right disinfectant?

With all the different efficacy spectra, it is not easy for a layperson to know which product is best for their own requirements. If you only use disinfectants for private purposes – for example to disinfect your hands after a bus ride – a classic, alcohol-based disinfectant such as Sterillium® is a good choice. It comprehensively protects you against bacteria, yeasts, and enveloped viruses and thus arms you against most pathogens found in everyday life. Since Sterillium® also provides the label "limited spectrum virucidal activity", you also have effective protection against noroviruses.

When choosing the right disinfectant, it is always good to know which pathogen you are dealing with. This is especially true in the health sector. When hospital or nursing home employees know which viruses or bacteria their patients are confronted with, they can better target infections. This means they don’t have to use disinfectants with the broadest spectrum of efficiency. In this way, outbreaks within clinics, hospitals and nursing homes can be better prevented overall [4].

A man takes disinfectant from a dispenser. — A classic, alcohol-based disinfectant protects against many everyday pathogens.

What about personal preferences?

Besides the type of pathogen, other subjective factors also play a role in the choice of disinfectant. Those who value an odourless product can choose Sterillium® classic pure – the fragrance-free version of Sterillium®. The type of active ingredient can also influence the choice. For some people, for example, a propanol-based product like Sterillium® feels better on the hands. Others, however, prefer an ethanol-based disinfectant like Sterillium® med.

But no matter what your preferences are, the Sterillium® product family provides the right disinfectant for everyone. You can find a good overview of the different Sterillium® products here.