Agrobacterium species in bacteraemias, Switzerland, 2008 to 2019: a molecular epidemiological study

Background: Agrobacterium spp. are infrequent agents of healthcare-associated outbreaks with bloodstream infections from a common point source. It is unclear, however, if outbreaks also occur on a national level. Our aim was to investigate potential Agrobacterium spp. clusters within Switzerland by whole genome sequencing.Methods: Nationwide descriptive study of cases in Switzerland, based on a prospective surveillance system (Swiss Centre for Antibiotic Resistance, anresis.ch), from 2008 to 2019. All patients with Agrobacterium spp. isolated from blood cultures were identified. A survey sent to the laboratories collected epidemiologic parameters of the patients, susceptibility testing, and additional cases. Whole genome sequencing (WGS) of the clinical isolates available was performed, and their relatedness investigated by SNP variant calling analysis.Results: We identified 36 cases of Agrobacterium spp. from blood samples. Besides one previously identified cluster, no further clusters at healthcare institution level were identified. WGS-based typing of 22 isolates showed no close clonal relationship between the cases besides the one previously established cluster.Conclusion and Relevance: Healthcare-associated Agrobacterium spp. bacteraemias from a point source may occur but seem to be an exception. There was no hint for an inter-institutional transmission. Multiple cases of invasive Agrobacterium spp. at one healthcare institution should prompt an outbreak investigation.