Sani Marc Group’s virtual magazine

Microorganism Resistance to Sanitization: Myth or Fact?


Much more fact than myth! When it comes to preventing bacterial outbreaks in the food industry, proper cleaning and sanitization are obviously essential to keep bacterial populations under control.

What is sanitization?

In any given bacterial population, the bacteria do not all react in the same way toward a specific dose of sanitizer. The most common sanitizers are chlorine and its derivatives, iodine derivatives, quaternary ammoniums, hydrogen peroxide, anionic acids and peracetic acids. Under normal exposure conditions, a sanitizer is capable of destroying 99.999% of bacteria present – the equivalent of a 5 log reduction. In other words, an initial population of one million bacteria per cm2 prior to sanitization can be expected to be reduced to 10 bacteria per cm2 following sanitization. The role of the sanitizer therefore is to reduce the bacterial population to a safe level to ensure food is safe for consumption and to preserve its organoleptic properties. These properties include aspects such as the colour, smell, appearance and texture of the food.

The phenomenon of bacterial resistance

The 10 bacteria that were not destroyed during sanitization could potentially withstand subsequent sanitization and become the source of future contamination. Because they were not destroyed, these remaining bacteria therefore have the capacity to proliferate, especially when exposed to food. When this occurs, the bacterial population no longer responds to the normal dose of sanitizer. The food plant now faces a problem because its routine sanitization process no longer works.

Although the risk of microorganism resistance is much lower with disinfectants than with antibiotics due to the fact that the mode of action of disinfectants involves a broad spectrum of activity, such resistance does occur from time in time. For example, the outer membrane of Gram-negative bacteria contain constituents that form a barrier against certain molecules such as quaternary ammoniums, resulting in bacterial resistance to this type of sanitizer. This resistance effect can be countered, however, by varying the nature of the sanitizer used.

Bacterial resistance through biofilm

The most common mode of bacterial resistance lies in biofilm formation. Certain bacteria secrete a polysaccharide that forms a matrix and traps the bacteria inside, thereby shielding them from the onslaught of sanitizers. Even though they are trapped inside the biofilm, the bacteria can nevertheless contaminate food that comes into contact with its surface. To reach the bacteria, the biofilm has to be destroyed – a task that’s more complicated than it seems because biofilm can be very difficult to remove from surfaces. However, studies conducted by Sani Marc have shown that periodic treatment with BioDestroy can effectively destroy the biofilm and the bacteria trapped inside.

Overcoming resistance

No matter how resistant the bacteria may be, they have be eliminated to completely resolve the contamination problem. The solution? A high dose of an alternative sanitizer. Peracetic acid is the ideal choice for effectively eliminating contamination.
In light of the evidence that microorganisms can acquire a certain level of tolerance or resistance to environmental stressors, a rigorous cleaning and sanitization plan for all equipment must be adhered to in order to effectively monitor possible cases of contamination. Normally, such operations are undertaken only after all cleaning and sanitization requirements have been fully met.


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