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Chapter 1
The S. Typhimurium strains studied have an antigenic structure 4,5,12;i:2
and its monophasic variant 4,5,12;i:- [1]. Together these antigenic
classifications accounted for 35% of all cases of Salmonella submitted to
the NSLRL in 2009 for typing [59]. In recent years there has been a
dramatic increase in the reported cases of the monophasic serovar
4,5,12:i:-, this phenomenon has also been seen in many other member
states in Europe [60]. Two strains of S. Typhimurium studied in this
research have a PFGE profile STYMXB.0131, this PFGE profile has been
implicated in numerous outbreaks throughout Europe with the number of
reported cases increasing by 321% in the UK and 414% in France over a 4-5
year period [60]. In a collaborative report of EU states, Hopkins et al.
identified the PFGE profile STYMXB.0131 in 28% of monophasic
Typhimurium strains assessed (n=114). This PFGE profile was previously
associated with S. Typhimurium with the definitive phage type DT193 and
phage type PT507 in Finland, the Netherlands and the UK [60]. The
monophasic S. Typhimurium was initially traced to pork products, however
it has also been found in poultry, cattle, non-domestic birds, broilers and
humans [61]. Due to the rapid dissemination of monophasic S.
Typhimurium the research described in this thesis also investigated if this
variant had distinctive properties that enhanced biofilm formation on
contact surfaces, although it is deemed as typically very similar to S.
Typhimurium at a molecular level [61]. The PFGE profile for the two
STYMXB.0131 strains is also provided courtesy of the NSSLRL (see Appendix
3).
1.14. Salmonella enterica serovar Enteritidis
Salmonella Enteritidis has the antigenic structure of 1,9,12 g, m –; [1].
Although S. Enteritidis has been reported in poultry as far back as 1930’s,
up until the 1970s, there were relatively few reports in poultry, eggs or in
human cases [6]. As previously discussed, it is suspected that vaccination
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