**4.5 The EAF plasmid**

Typical EPEC strains possess a large virulence plasmid called the EPEC adherence factor (EAF) plasmid [9], which varies in sequence among different EPEC strains but is somewhat conserved [12]. The EAF plasmid pMAR2 is found among strains of the EPEC1 lineage, whereas pB171 is more common among EPEC2 strains [50, 51]. Two sets of genes located on the EAF plasmid are important for pathogenicity: the *bfp* gene cluster encoding BFP [38] and the *per* locus encoding a transcriptional activator called plasmid-encoded regulator (Per) [51]. Both BFP and PerA have been shown to contribute to virulence in human volunteers [52]. Between pMAR2 and pB171, the *bfp* and *per* loci share 99% sequence similarity [50]. Studies of comparison genomics of the EAF plasmids from varied EPEC phylogenomic lineages demonstrated significant plasmid diversity among isolates within the same phylogenomic lineage [53].
