Objective To investigate the whole genomic characteristics and phylogenetic relationships of clinical isolates of enteroaggregative Escherichia coli (EAEC) in diarrhea outpatients in Pudong New Area, Shanghai.

Methods Based on the diarrheal disease surveillance network in Pudong New Area, Shanghai, whole-genome sequencing was performed on a total of 55 EAEC strains isolated from fecal samples of the diarrhea outpatients from January 2015 to December 2019. The genome analyses based on raw sequencing data encompassed genome size, coding genes, dispersed repeat sequences, genomic islands, and protein coding regions, and pan-genome analyses were conducted simultaneously. Contigs sequences assays were performed to analyze molecular characteristics including serotypes, antibiotic resistance genes, and virulence factors. The phylogenetic clusters and multilocus sequence typing (MLST) were identified, and a phylogenetic tree was constructed.

Results EAEC exhibited an open pan-genome. The predominant serotype of EAEC in diarrhea outpatients in Pudong New Area was O130:H27, and the carriage rate of β-lactam resistance genes was the highest (67.27%, 37/55). A total of 29 virulence factors and 106 virulence genes were identified, phylogenic group B1 was the predominant group, and clonal group CC31 was the dominant clonal group. The strain distribution was highly heterogeneous.

Conclusion The genomic characteristics of EAEC displayed significant strain polymorphism. It is necessary to develop effective strategies for differential diagnosis and improve detection capabilities for infection with EAEC of different serotypes and genotypes.