Food pathogens on fresh foods and equipment surfaces are scary. You probably have been told that you can easily spray wash pathogens from a surface and for extra security you can use a sanitizer and a brush. This scenario is partially true. In many cases no amount of washing and scrubbing seems to remove the contamination. As it turns out, the vast numbers of pathogens on fresh produce and equipment are tightly packed into biofilms and the biofilms are tightly adhering to food and equipment surfaces. Pathogens do not live as solitary cells (“planktonic”) but in moist communities consisting of more than one species encased in extracellular, glue like matrix called biofilm slime. What’s this about?
Planktonic cells weakly attach to damp surfaces like plant and animal tissue, glass, stainless steel, rollers, plastics, rubber, and any damp surface using weak, reversible bonds. These cells may be washed off. However, if the surface is allowed to condition and cells attach to a conditioned surface a biofilm develops. Cells anchor and encase themselves by secreting extracellular polymeric substances (“EPS”). The EPS holds cells onto the surface, acts as a magnet for other floating cells, and protects cells. Imagine the biofilm slime to be a fortress less than 1000th of an inch to visible to the naked eye.
The story gets more complicated as biofilm slimes grow. Many different cell species may attach and the biofilm slime responds to these new intruders. The net result is that all the cells in a biofilm slime work toward self-preservation creating a safer habitat for all slime members. Nutrients diffuse into the biofilm and waste diffuses out. In distances measured in less than 1000th of an inch cells can become inactive (dormant) because of limited nutrient access. The combination of slow diffusion, cellular inactivity and diversity make biofilm slimes highly resistant to chemical applications. Once slimes develop they are nearly impossible to remove.
Biofilm slimes grow and at certain times shed free floating cells and pieces of biofilm slime into the environment. The free floating cells can colonize a new surface or instantly adhere to an existing biofilm slime. In the same manner, drifting biofilm slime, weather released or sheared off by a boot, wheel, or by equipment can immediately stick and anchor to any moist surface. What does this mean for food safety? You need to prevent biofilm slimes from starting. Sanitizers need to be used to prevent surface conditioning and this requires multiple interventions.