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English: Genetic events contributing to the evolution of EIEC from ancestral commensal E. coli. The acquisition of the pINV by HGT is a major evolutionary event toward pathogenicity. This can be accompanied by the sporadic acquisition of entire or incomplete SHI-1 PAI and incomplete SHI-2 and SHI-3 PAIs. Rarely, also incomplete SRL PAI are acquired by EIEC genomes. The absence of ompT and the loss of cadaverine synthesis (usually resulting from cadC silencing) counterbalance the gain of virulence-associated determinants. The inactivation of speG (involved in spermidine acetylation) and nad (involved in NAD biosynthesis) is regarded as emergent pathoadaptive mutations in EIEC.