Methods available for the sub-typing of Escherichia coli O157

The epidemiological investigation of Escherichia coli O157 is complicated b y the lack of heterogeneity between strains responsible for the majority of cases of infection. As a consequence it is difficult to reliably cluster t ogether an outbreak strain and differentiate it from other sporadically occ urring isolates. The methods available for the subtyping of E. coli O157 va ry in their speed, technical complexity, cost and ability to discriminate r eliably between strains, with many of the recently developed methods target ing the genome to provide differentiation. No single typing method is indiv idually superior, and ideally a combination of techniques should be employe d depending on the level of discrimination required and time or resources a vailable. The aim of this review is to consider the relative merits of the available typing methodologies with particular emphasis on those which may find application in a diagnostic laboratory.