Complete genome of Escherichia coli sequence type 73 with acquired blaTEM-1 and high genotypic virulence load identified in human saliva

Objectives

Escherichia coli sequence type (ST) 73 is a pandemic lineage of the ExPEC (Extraintestinal Pathogenic E. coli) family associated with conserved virulence. We report the complete genome of a genomically hypervirulent E. coli ST73 strain isolated from the oral cavity of a patient with a diagnosis of treatment resistant schizophrenia and receiving clozapine treatment.

Methods

E. coli strain GABEEC132 underwent second and third generation sequencing with Illumina and Oxford-Nanopore-Technologies (ONT) platforms. Antibiotic resistance genes (ARGs) and virulence factors (VFs) were bioinformatically identified using the NCBI-AMR-Finder-Plus database and Virulence-Factors-database (VFDB), respectively. To contextualize the genome within a broader epidemiological framework, phylogenetic analysis was conducted using representative genomes of E. coli ST73 O6:H1 (n = 55).

Results

E. coli strain GABEEC132 was identified as possessing the O6:H1 serotype and classified within the B2 phylogroup. The strain exhibited a high genomic virulence load, encoding for 194 VFs. Additionally, it encoded three ARGs, including an acquired blaTEM-1 located on a rep_cluster_2350 8 237 Kb mobilisable plasmid, presenting phenotypic resistance to ampicillin and piperacillin.

Conclusion

This report provides novel insights into the oral prevalence of genotypically hypervirulent and drug-resistant E. coli ST73, a pandemic lineage.