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Chapter 2
although S. Senftenberg was the serovar most frequently isolated from the
Norwegian food processing plants investigated, it persisted in the
environment for a shorter period of time than the other serovars studied.
Therefore the authors concluded that the frequent isolation of S.
Senftenberg may be due to presence in raw material and not relating to its
ability to form a biofilm [56]. This research provided by Vestby et al.
suggests that the S. Senftenberg recovered from the surface may have
been in a planktonic form on the surface while the other strains recovered
were more representative of dense biofilm formers due to repeated
isolation of specific strains from the environment [56].
Rodrigues et al. suggested that S. Enteritidis biofilm formation may be
strain dependent but that the volume of biofilm formed may also be
surface or substratum dependent. Rodrigues et al. reported that isolates
recovered from food and reference isolates formed a less dense biofilm
than clinical isolates of S. Enteritidis using the microtitre plate based
system [98]. These findings correspond with Castelijn’s hypothesis that
clinical isolates may have a higher propensity to form a more dense biofilm
than strains associated with food or food processing environments [32].
Other studies were unable to confirm a relationship between source or
origin of isolates and ability to form a biofilm/density of biofilm formed [96,
111]. However given the small test sample size, such as a total of five S.
Enteritidis isolates used by Rodrigues et al.[98] incorporating only 1 food
isolate it is difficult to determine if this trend would be still be evident with
a larger sample size. As a result, it may be more accurate to conclude that
the biofilm density is more likely to be strain dependent than source
dependent.
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