STX2 and infection: Infection with strains producing Stx2a may lead to extraintestinal complications, although the cause of the latter is likely to be multi-factorial and can include the constitutive regulation of stx gene expression; antibiotic usage during the prodromal diarrheal phase, inducing the phage-mediated lytic cycle; the presence or absence of additional E. coli virulence factors; and variations in host responses to toxins, which all contribute to the outcome of infection.