Decontamination of knives used in a slaughterhouse by a commercial non-thermal UV-C treatment.

To assess the antimicrobial effect of a commercial UV-C system, knives inoculated with and as well as naturally contaminated and collected from the wet and clean area of a slaughterhouse knives were examined. For inoculated knives, UVC treatment for 30 s reduced mean counts by 5.1 log CFU cm and mean counts by 4.5 log CFU cm. The presence of blood lowered mean reductions to 3.4 log CFU cm for and to 2.5 log CFU cm for . The presence of fat had a greater negative impact on the efficacy of the UV-C treatment resulting in mean reductions <1.8 log CFU cm. For naturally contaminated knives from a slaughterhouse, total viable counts (TVC) before UV-C treatment varied considerably (wet area: 2.0-6.0 log CFU cm, clean area: 1.0-3.0 log CFU cm). UV-C treatment for 30s reduced mean TVC by 0.8 log CFU cm (wet area) and 0.6 log CFU cm (clean area), but the effect varied greatly between individual knives. Thus, under commercial conditions, the antibacterial effect of UV-C for the decontamination of knives is affected by the presence of additional contaminations like blood or fat. The adequate cleaning of the knives prior to UV-C decontamination is therefore of central importance.