4. Discussion
The isolation of STEC from foods remains a challenge because STEC are
very often present with other non-pathogenic E. coli or Enterobacteriaceae
and no selective condition has been identified which is unique to the
STEC pathotype of E. coli. Since no unique differential characteristic
has been identified, other than verotoxin expression, this means that
isolation requires that potentially large numbers of colonies must be
screened individually for VT genes or expression. Diverse STEC have
been successfully isolated from foods, by identifying VT positive colonies
grown on a relatively permissive agar medium by colony immunoblot
(Atalla et al., 2000) or colony hybridization (Barlow et al., 2006). But
the lack of uptake of these methods reflects the technical challenges in
adopting these methods outside of a research laboratory.
Alternatively, isolation media for specific subgroups of STEC
have been developed which are based on selective or differentia