Thirty-eight strains of Shiga toxin-producing Escherichia coli
(STEC) were characterised in terms of biochemical
properties, enterohaemolysin production and plasmid carriage. A wide variation in the biochemical properties was
observed among the STEC, with 14 distinct biotypes identified. Biotype 1 was the most common, found in 29% of the strains. Enterohaemolysin
production was detected in 29% of the strains. Most of the bacterial strains (95%) carried one or more plasmids and considerable heterogeneity
in size and combinations was observed. Seven distinct plasmid profiles were identified. The most common profile, characterised by the presence
of a single plasmid of ~90 kb, was found in 50% of these strains. These data indicate extensive diversity among STEC strains. No correlation
was found among biotype, serotype, enterohaemolysin production and plasmid profile.