Agrobacterium spp. nosocomial outbreak assessment using rapid MALDI-TOF MS based typing, confirmed by whole genome sequencing.
Background
A 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.


Methods
Cases 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.


Results
We 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.


Conclusions
We 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.
['Casanova|Carlo|C|0000-0002-7888-6329', 'Lo Priore|Elia|E|', 'Egli|Adrian|A|', 'Seth-Smith|Helena M B|HMB|', 'Räber|Lorenz|L|', 'Ott|Daniel|D|', 'Pflüger|Valentin|V|', 'Droz|Sara|S|', 'Marschall|Jonas|J|', 'Sommerstein|Rami|R|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D060054:Agrobacterium D015373:Bacterial Typing Techniques D003428:Cross Infection D004196:Disease Outbreaks D016521:Electrophoresis, Gel, Pulsed-Field D005260:Female D016680:Genome, Bacterial D005858:Germany D016905:Gram-Negative Bacterial Infections D006801:Humans D008297:Male D008875:Middle Aged D010802:Phylogeny D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization D062606:Tertiary Care Centers D000073336:Whole Genome Sequencing D055815:Young Adult
Agrobacterium Nosocomial outbreak MALDI-TOF MS Whole genome sequencing Rhizobium