Abstract
BackgroundA number of episodes of nosocomial Agrobacterium spp. bacteremia (two cases per year) were observed at Bern University Hospital, Switzerland, from 2015 to 2017. This triggered an outbreak investigation.MethodsCases of Agrobacterium spp. bacteremias that occurred between August 2011 and February 2017 were investigated employing line lists, environmental sampling, rapid protein- (MALDI-TOF MS), and genome-based typing (pulsed field gel electrophoresis and whole genome sequencing) of the clinical isolates.ResultsWe describe a total of eight bacteremia episodes due to A. radiobacter (n = 2), Agrobacterium genomovar G3 (n = 5) and A. pusense (n = 1). Two tight clusters were observed by WGS typing, representing the two A. radiobacter isolates (cluster I, isolated in 2015) and four of the Agrobacterium genomovar G3 isolates (cluster II, isolated in 2016 and 2017), suggesting two different point sources. The epidemiological investigations revealed two computer tomography (CT) rooms as common patient locations, which correlated with the two outbreak clusters. MALDI-TOF MS permitted faster evaluation of strain relatedness than DNA-based methods. High resolution WGS-based typing confirmed the MALDI-TOF MS clustering.ConclusionsWe report clinical and epidemiological characteristics of two outbreak clusters with Agrobacterium. spp. bacteremia likely acquired during CT contrast medium injection and highlight the use of MALDI-TOF MS as a rapid tool to assess relatedness of rare gram-negative pathogens in an outbreak investigation.
Highlights
A number of episodes of nosocomial Agrobacterium spp. bacteremia were observed at Bern University Hospital, Switzerland, from 2015 to 2017
For Enterococcus faecium and Staphylococcus aureus, it is more controversially discussed whether the discriminatory power of MALDI-TOF MS is sufficient for strain typing [24, 29, 30], indicating that the applicability of this technique may depend on the bacterial species
We investigated a series of nosocomial Agrobacterium spp. bacteremia episodes observed at Bern University Hospital, Switzerland, and used MALDI-TOF MS-based typing as first-line method to determine relatedness of the isolates, which was subsequently confirmed by highresolution whole genome sequencing (WGS)-based typing
Summary
A number of episodes of nosocomial Agrobacterium spp. bacteremia (two cases per year) were observed at Bern University Hospital, Switzerland, from 2015 to 2017. Bacteria of the genus Agrobacterium are environmental gram-negative rods, present in soil and plants They are rare opportunistic human pathogens, with the majority of infections reported in immunocompromised hosts, such as oncology patients, the elderly, and neonates [1,2,3]. We investigated a series of nosocomial Agrobacterium spp. bacteremia episodes observed at Bern University Hospital, Switzerland, and used MALDI-TOF MS-based typing as first-line method to determine relatedness of the isolates, which was subsequently confirmed by highresolution WGS-based typing
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