Distribution of serine protease autotransporters of Enterobacteriaceae in typical and atypical enteroaggregative Escherichia coli.

Enteroaggregative Escherichia coli (EAEC) is an agent of acute and persistent diarrhea worldwide, categorized in typical or atypical subgroups. Some EAEC virulence factors are members of the serine protease autotransporters of Enterobacteriaceae (SPATE). The presence of SPATE-encoding genes of different E. coli pathotypes was searched in a large collection of EAEC strains, and a possible association between SPATEs and E. coli phylogroups was investigated. Among 108 typical and 85 atypical EAEC, pic was the most prevalent gene, detected in 47.1% of the strains, followed by sat (24.3%), espI (21.2%), pet (19.2%), sepA (13.5%), sigA (4.1%), eatA (4.1%), vat (1.0%), espP and tsh, detected in one strain (0.5%) each; while epeA and espC were not detected. Phylogenetic analysis demonstrated that 39.9% of the strains belonged to group A, 23.3% to B1, 10.9% to B2, 7.8% to D, 8.8% to E and 1.5% to F. The majority of the SPATE genes were distributed in typical and atypical strains without association with any phylogroup. In addition, pic and pet were strongly associated with typical EAEC and sepA was detected in close association with atypical EAEC. Our data indicate that SPATEs may represent important virulence traits in both subgroups of EAEC.