IS inactivation of vtx2 in O157:H7 from Swedish cattle. O157_IS_vtx2_SVA

Verotoxigenic E. coli (VTEC, a.k.a. STEC) O157:H7 is a major zoonotic pathogen with asymptomatic ruminants as the main reservoir. Swedish cattle isolates of O157:H7 were found to surprisingly often have IS629 class III insertion sequences in the gene encoding verotoxin 2, the primary VTEC virulence factor. This is likely to cause inactivation of vtx2 and thereby loss of virulence. Sequencing was performed to investigate the patterns of insertion, and the extent of deletions likely to have been caused by IS element activity.