Comparison of the novel 78-kb PAI reported in this study, with the 89-kb PAI reported in epidemic strains from two outbreaks in China. The key factors for virulence of epidemic strains are indicated in green, including SalKR, NisKR, a Type IV-Like Secretion System and a Tn916 element. The antibiotic-resistance genes are shown in red. Three regions in the 89-kb PAI are absent from the 78-kb PAI. No virulence-related genes were found within these regions. 