Assessment of Organic Materials and Microbial Components on Hygienic Surfaces

Abstract

The presence of the inert components of organic soil on hygienic surfaces provides a challenge for cleaning procedures, and may affect the survival of any microorganisms, afford protection from disinfection, enhance attachment to the surface, and potentially provide nutrient. Substratum coupons are frequently re-used in fouling and cleaning experiments. When used stainless steel (2B finish) substrata were stained using fluorescent dye, organic material was detected, and the surface topography of the substratum was reduced as the accumulating soil filled grain boundaries, indicating different behaviour of microorganisms and organic material on the surface. Few attempts have been made to assess the presence of both microorganisms and other material on hygienic surfaces, although for reasons given above, this should certainly be considered. Differential fluorescent staining and assessment of the contribution of both components to surface coverage provides a relatively simple method. The effect of a protein film (bovine serum albumin; BSA) on the retention on and removal of Staphylococcus aureus from titanium surfaces with defined topographical features (pits 0.2μ–2.0μ diameter) was monitored. Surfaces were spray-cleaned with sodium dodecyl sulphate (SDS). Cells were more easily removed from surfaces than organic material. For features which were larger than the S. aureus cells (i.e. 2 ?m diameter), cells were easily removed by cleaning, but in the presence of BSA, cells were retained at significant levels. The presence of organic material on surfaces alters their cleanability and should be monitored along with the presence of microbial cells during cleaning and sanitising regimes.