Dissemination of Verona Integron-encoded Metallo-β-lactamase among clinical and environmental Enterobacteriaceae isolates in Ontario, Canada

Abstract

Surveillance data from Southern Ontario show that a majority of Verona Integron-encoded Metallo-β-lactamase (VIM)-producing Enterobacteriaceae are locally acquired. To better understand the local epidemiology, we analysed clinical and environmental bla_VIM-positive Enterobacteriaceae from the area. Clinical samples were collected within the Toronto Invasive Bacterial Diseases Network (2010-2016); environmental water samples were collected in 2015. We gathered patient information on place of residence and hospital admissions prior to the diagnosis. Patients with and without plausible source of acquisition were compared regarding risk exposures. Microbiological isolates underwent whole-genome sequencing (WGS); bla_VIM carrying plasmids were characterized. We identified 15 patients, thereof 11 with bla_VIM-1-positive Enterobacter hormaechei within two genetic clusters based on WGS. Whereas no obvious epidemiologic link was identified among cluster I patients, those in cluster II were connected to a hospital outbreak. Except for patients with probable acquisition abroad, we did not identify any further risk exposures. Two bla_VIM-1-positive E. hormaechei from environmental waters matched with the clinical clusters; plasmid sequencing suggested a common ancestor plasmid for the two clusters. These data show that both clonal spread and horizontal gene transfer are drivers of the dissemination of bla_VIM-1-carrying Enterobacter hormaechei in hospitals and the aquatic environment in Southern Ontario, Canada.

Figure 1

Single nucleotide polymorphisms (SNP) analysis for bla_VIM-1-carrying Enterobacter hormaechei.

Figure 2

Inpatient and outpatient healthcare contacts in the Toronto Invasive Bacterial Diseases Network surveillance area as well as hospital admissions abroad of patients with bla_VIM-1-positive Enterobacteriaceae. Each black or grey bar represents a hospital visit or admission with the different hospitals represented by different letters, and out-patient visits only marked with an asterisk.

Figure 3

Comparison of IncR plasmids between bla_VIM-1 carrying E. hormaechei isolates from cluster I (environmental isolate Eho-E1 and clinical isolate Eho-5) and cluster II (clinical isolate Eho-7); for more information about IncR plasmids, see Supplementary Figs. 2–6.