A little biology
In nature there are countless microorganisms, usually unicellular microscopic living beings, most of which are harmless, beneficial, and even essential for human existence. They help in the absorption of food, prevent the proliferation of pathogens, produce essential vitamins, or intervene in the fermentation of foods such as beer, wine, bread, or dairy products.
But in nature we also find other families of microorganisms that are not harmless, causing infectious diseases, having been responsible for some of the greatest annihilations throughout human History. Diseases such as cholera, typhus or tuberculosis are caused by bacteria. Their control is therefore crucial for human health.
The generic concept of microorganism encompasses different families of microscopic living beings: from bacteria, fungi, molds, algae, also including organisms such as amoebae (protozoa), to microanimals such as mites.
The terms microbe and bacteria are often used interchangeably. But are they the same? Bacteria and microbes are equivalent?
No, not really. By bacteria we only understand prokaryotic unicellular organisms (lacking a nucleus) while microbe, a broader concept, encompasses both bacteria and eukaryotic unicellular beings (that have a cell nucleus) such as molds, fungi and algae.
Viruses by definition are not living things. They are simpler entities than a bacterium, they are considered obligate intracellular parasites, that is, they are incapable of surviving independently, and they need to infect a host (a prokaryotic or eukaryotic cell) in order to replicate their RNA or DNA sequences, and to be able to multiply. They use the cellular machinery and their biochemical resources to synthesize their structures and replicate their genetic material, subsequently assembling each of these parts and giving rise to a new viral particle.
Like bacteria, there are countless different classes of viruses, most of which are harmless to humans, but some others cause mild illnesses such as the flu (influenzavirus), or serious diseases such as AIDS (HIV), herpes (herpesvirus), or Atypical pneumonia such as SARS, MERS or more recently SARS Cov-2, the cause of Covid-19.
Just as the terms bacterium, microbe or virus, refer to microorganisms that can be both beneficial (commensal) and harmful, to encompass and distinguish the latter it is preferable to use the concept of pathogen.
What are antimicrobial agents?
When we speak of antibacterial, we refer to substances that act specifically and only against bacteria.
The more generic term antimicrobial is applied to those substances with a broader field of activity, capable of inhibiting growth or even eliminating both bacteria and algae, molds and even certain viruses.
The antimicrobial active principles constitute a wide spectrum of chemical substances that, although they must be harmless to humans, act by interfering in one or more of the cellular or biochemical mechanisms essential for the activity and survival of pathogens. These mechanisms of inhibition or interference are called antimicrobial targets. Some of the main known targets of action are:
Antimicrobial additives can induce the degradation of the genetic material of pathogenic microorganisms, preventing their ability to replicate and / or reverse transcription or transcription, and therefore, their viability
Antimicrobial agents can also increase the oxidation rate of some cellular metabolic reactions, resulting in irreversible internal damage, preventing the viability of the microorganism.
Damage to the
Likewise, antimicrobial agents can induce the degradation of the cell membrane, cell wall or viral envelope, causing its collapse, generating irreversible structural damage and consequently the destruction of the pathogen and the loss of its viability
Inhibition of protein synthesis and / or degradation
Finally, some antimicrobial agents can damage some proteins, deactivating their functionality and causing damage to fundamental metabolic processes in organisms.
The range of active ingredients with antimicrobial activity is very wide and complex, each with a specific spectrum of action, benefits, and limitations of use. From inorganic substances such as some metals, to organic substances such as phenolic molecules, quaternary ammonium compounds or sulfur derivatives.
How the effectiveness of antimicrobial agents is verifieds?
Each type of pathogenic microorganism offers a different resistance to different antimicrobial agents. It is therefore crucial to test the resistance of the microorganism in question to the antimicrobial agent.
At Supersum we start from the basis of this concept, and we work with differentiated, broad spectrum or specific antimicrobial agents that can interact with most of the pathogens that we can find: from bacteria, fungi and molds, protozoa, algae, to several of the viruses, mainly RNA viruses such as SARS COV-2 (COVID-19) or the influenza virus (inluenzavirus).
There are different standardized regulations to study the response of microorganisms to different antimicrobial agents. The most widespread methods in Europe are:
• ISO 22196:2011, antibacterial effectiveness test
• ISO 16869:2008, antifungal effectiveness test
• ISO 846:2019, antibacterial and antifungal effectiveness test
• ISO 21702:2019, antiviral effectiveness test
ISO 22196:2011. Antibacterial activity of plastic and non-porous materials
Briefly, the method checks the antibacterial efficacy of a compound or additive introduced in a plastic matrix or other non-porous material. At a technical level, the behavior of a known bacterial inoculum that is deposited on reference pieces and pieces with antimicrobial treatments is studied. An incubation of the initial inoculum is carried out on each one of these pieces for 24 hours at 35 / 36ºC and a relative humidity of not less than 85/90%. Subsequently, a count is made by different methods and the result is expressed in terms of CFU (colony forming units), comparing the evolution between reference samples (without antimicrobial agent) versus others that contain it. Quantitative values are taken to "R" values (logarithmic reduction) and to percentage of net cell death (%). The higher the R value, the smaller the volume of microorganisms detected in the sample under study, and, consequently, the greater the effect of the antimicrobial agent. It is homologous to JIS Z 2801: 2010.
ISO 16869:2008. Antifungal activity in plastic materials (and porous foams)
Briefly, the method checks the antifungal efficacy of a compound or additive introduced or adhered to a plastic matrix. At a technical level, the behavior of a known fungal inoculum (mixture of 5 fungi) that is deposited on reference pieces and pieces with antimicrobial treatments, embedded in a semi-solid medium (agar), is studied. An incubation of the initial inoculum is carried out on each of these pieces for 21 days at 24 / 25ºC and a relative humidity of not less than 85%. After the incubation period, the result is visually checked and classified into different growth levels (0.1 and 2). This degree of growth or no growth observed will determine the different resistance and / or antifungal activity of the tested materials.
ISO 846:2019, The methodologies are quite similar to the previous two, since this standard generally brings together the measurement of the antibacterial and / or antifungal efficacy of various materials. It is broader in the matrix of types of materials to be tested but the methodologies, tools and classification tables do not differ much from ISO 22196 or ISO 16869. At the normative level, it is homologous to some American ASTM standards, such as G21 in the case of fungi.
ISO 21702: 2019. Antiviral activity on plastics and other non-porous surfaces
Briefly, the method tests the antiviral efficacy of plastic materials and other non-porous surfaces. At a technical level, it is fundamentally based on the basic methodologies used in ISO 22196 but with the pertinent modifications required by the use and manipulation of viruses, introducing control parameters based on the viability or susceptibility to the virus of the support cells used, cytotoxicity intrinsic characteristics of the materials, as well as the methods of titration or counting of the viruses (TCID50) and the method of detection of their degree of replication or multiplication within cells (cytopathic effect). The standard specifies that the test must be carried out at 25ºC for 24 hours at a humidity not lower than 90%, but these requirements can be modified at the customer's request.
At a technical level, a known viral titer or suspension is deposited on the surface of pieces with antiviral treatments and pieces of the same material without antiviral treatment.
After the determined time, the viral extension of the surface is collected and inoculated on viable eukaryotic cells in order to incubate them and observe the cytopathic effect in order to be able to calculate a crude viral titration method (TCID50 or PFU) and determine the antiviral activity value on a logarithmic scale (R) and the percentage of net reduction (% viral death). These calculations are carried out in a very similar way to those indicated in ISO 22196.