IncHI1 plasmids are epidemic vectors that mediate transmission of tet (X4) in Escherichia coli isolated from China.

The widespread dissemination of tigecycline-resistant is a major threat to public health. This data suggests careful use of tetracycline on farms is important to limit spread of resistance to tigecycline. Multiple mobile elements carrying (X4) are in circulation with IncHI1 plasmids the dominant vector in this setting.