Comparative genomics of Chinese and international isolates of Escherichia albertii: population structure and evolution of virulence and antimicrobial resistance
Authors: Luo Lijuan , Wang Hong , Payne Michael , Liang Chelsea , Bai Li , Zheng Han , Zhang Zhengdong , Zhang Ling , Zhang Xiaomei , yan Guodong , Zou Nianli , Chen Xi , Wan Ziting , Xiong Yanwen , Lan Ruiting , Li Qun 
Published: February 2021

Escherichia albertii is a newly recognized species in the genus Escherichia that causes diarrhea. The population structure, genetic diversity and genomic features has not been fully examined. Here, 169 E. albertii isolates from different sources and regions in China were sequenced and combined with 312 publicly available genomes for phylogenetic and genomic analyses. The E. albertii population was divided into 2 clades and 8 lineages, with lineage 3 (L3), L5 and L8 more common in China. Clinical isolates were observed in all clades/lineages. Virulence genes were found to be distributed differently among lineages: subtypes of the intimin encoding gene eae and the cytolethal distending toxin (Cdt) gene cdtB were lineage associated, the second type three secretion system (ETT2) island was truncated in L3 and L6. Seven new eae subtypes and 1 new cdtB subtype (cdtB-VI) were found. Alarmingly, 85.9% of the Chinese E. albertii isolates were predicted to be multidrug resistant (MDR) with 35.9% harboured genes capable of conferring resistance to 10 to 14 different drug classes. By in silico multi-locus sequence typing, majority of the MDR isolates belonged to 4 STs (ST4638, ST4479, ST4633 and ST4488). Thirty-four intact plasmids carrying MDR and virulence genes, and 130 intact prophages were identified from 17 complete E. albertii genomes. Ten plasmid replicon types were found to be significantly associated with MDR. The 130 intact prophages were clustered into 5 groups, with group 5 prophages harbouring more virulence genes. Our findings provided fundamental insights into the population structure, virulence variation and MDR of E. albertii.

Impact statement

E. albertii is newly recognized foodborne pathogen causing diarrhea. Elucidation of its genomic features is important for surveillance and control of E. albertii infections. In this work, 169 E. albertii genomes from difference sources and regions in China were collected and sequenced, which contributed to the currently limited genomic data pool of E. albertii. In combination with 312 publicly available genomes from 14 additional countries, the population structure of E. albertii was defined. The presence and subtypes of virulence genes in different lineages were significantly different, indicating potential pathogenicity variation. Additionally, the presence of multidrug resistance (MDR) genes was alarmingly high in the Chinese dominated lineages. MDR associated STs and plasmid subtypes were identified, which could be used as sentinels for MDR surveillance. Moreover, the subtypes of plasmids and prophages were distributed differently across lineages, and were found to contribute to the acquisition of virulence and MDR genes of E. albertii. Altogether, this work reveals the diversity of E. albertii and characterized its genomic features in unprecedented detail.

Data Summary

All newly sequenced data in this work were deposited in National Center for Biotechnology Information (NCBI) under the BioProject of PRJNA693666, including 6 complete genomes and raw reads of 164 E. albertii isolates.