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Chapter 6
model. The combination of surfaces was chosen with a view to ensuring
that the findings were relevant to food processing environments.
Chapter two presents an evaluation of the ability of S. enterica strains to
form biofilm on glass, stainless steel, polycarbonate plastic, glazed tile and
concrete after 48 hours and the density of the biofilm formed. Tile
supported more dense biofilm formation than any of the other surfaces.
This finding was consistent throughout the experiments as the number of
cells recovered from the tile surface was higher than all other surfaces
across all 13 strains tested and in each repeated test. Furthermore, when a
biofilm was developed for an extended time of 168 hours, as discussed in
chapter three, the association of increased biofilm density on tile was also
evident.
Further research in this area may help to clarify the relationship between
biofilm density and substrata. Previous research into the properties of
biofilm substrata has suggested that surface roughness may play an
important role in bacterial attachment [102, 164]. As described in chapter
2, when surface roughness was examined with atomic force microscopy
(AFM) glass was the least rough followed by tile, steel, polycarbonate and
concrete. It appeared that in general substrata with greater surface
roughness were associated with greater mean log density of cells
recovered from the surfaces. The exception was tile. Tile was more rough
than glass but less rough than other surfaces however by AFM although it
supported the most dense biofilm formation. This suggests there may be a
general relationship between surface roughness and density of biofilm
formed however other factors such as polarity may also contribute to initial
bacterial attachment to the surfaces [100], which may contribute to biofilm
formation. This or other properties may account for exceptional density of
biofilm formed on tile.
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