Antimicrobials: Improving Microbial Control
The Microbial Rule of 3….
The “Rule of Three” simply stated is – Does the system have Water, Temperature, and Carbon? If ‘yes’ then the product or system will be challenged by microorganisms. This first assessment defines if organisms can grow in your system. Biologically it is a bit more involved, but in many industrial settings and the standard environments of most consumer products, the rule of three is essentially fact. All living organisms need water but even humidity can provide enough moisture for microorganisms. All living organisms are limited by ranges of temperature, microorganisms are particularly adaptive to extremes but like to grow in temperatures we find comfortable. For nutrients, carbon is the basic component of organic molecules that microorganisms can use as nutrients. Again due to their adaptability, microorganisms can use virtually any carbon source as a nutrient source. Once microorganisms have become established, the challenge of controlling their effects is much greater. For some environments, this situation may be OK, but for others the material damage may require the elimination/replacement of the material or product.
When discussing microbial control the typical operative terms are as followed: preservation, sterilization, disinfection, sanitization, the “anti’s” (antimicrobial, antibacterial, antifungal, antialgal…etc), the “-stat’s” (bacteriostatic, fungistatic, algaestatic) and the “-cide’s” (microbicide, bactericide, fungicide, and algaecide…etc). As the terminology indicates the scope and application of an antimicrobial additive is tremendous. As likely users of antimicrobial products, it can be helpful to understand why they are needed and some best practices for effective implementation of their use. The principle function of antimicrobial testing is to help in this determination, and in establishing an effective quality control program that minimizes the cost, time and risk associated with unmanaged microbial control issues.
There are many misconceptions regarding the appropriate use of antimicrobials. For many products and applications, the use of antimicrobials is simply required to prevent the material from either spoiling or decaying. The challenge of material decay is not limited to microorganisms; for example, UV light, heat, and weathering also cause similar types of damage, which can lead to significant financial costs and safety issues. But unlike standard environmental conditions, microbes are adaptive in that they can change or acclimate to an infinite number of variables, exacerbating product degradation. This adaptability can create additional degradation issues, such as far reaching odors and potentially detrimental health effects.
Restating the question — ” Why are antimicrobials used?” From the Rule of 3 – if a product or system has the three critical components, be assured that environmental conditions are permissive to the growth of microorganisms.
Determining the appropriate test for antimicrobial performance, requires an good understanding of the additive used, the microorganisms of concern and an understanding of product manufacturing, intended use and durability. Many industrial test methods are available such as those from ASTM, ISO, or AATCC, but at time an optimized method will be better suited to the needs product development.