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Chapter 2
allowed increased removal after disinfection in comparison to the woven
materials with a higher surface area [67]. The aforementioned projects
each examined different finishes of a single surface material of steel [103],
glass [102] and synthesised plastic materials [67].
2.1.2. Strains/ Serovars
Rodrigues et al. confirmed that S. Enteritidis strains were able to form a
biofilm on kitchen surfaces such as silestone (impregnated with triclosan),
granite, marble and steel [98]. Through the use of staining and viable plate
counts Rodrigues et al. found that four of the five strains tested were more
adherent to marble than any other surface. Rodrigues also suggested that
there may be strain variability as in most instances the food isolate and
control isolate formed more dense biofilm than clinical isolates in a 6 well
microtitre plate model. The researchers incorporated multiple surfaces into
the biofilm model, however, all of the strains tested were S. Enteritidis. It
may have been of value to also investigate whether there was any interserovar
variation in the density of biofilm formed on the surfaces which has
been suggested elsewhere [56, 76, 165]. The authors did not incorporate
any sheer stress into the biofilm model design used. This may be
significant as the introduction of sheer stress has been identified as an
important variable in biofilm formation [116-117, 166].
2.1.3. Origin of strains
The source of origin of strains may have an impact on the ability of the
organisms to form a biofilm. Castelijn and colleagues reported that the
density of biofilm formed in altered concentrations of nutrient-rich typtone
soy broth (TSB) was related to the origin or source of the 51 S.
Typhimurium strains examined [32]. Both strains, traced to outbreaks and
to contaminated retail products resulted in dense biofilm formation at 25°C
and 37°C in the nutrient-rich and diluted media. However the isolates
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