Biotyping reveals loss of motility in two distinct Yersinia ruckeri lineages exclusive to Norwegian aquaculture

Abstract

The Gram-negative bacterium Yersinia ruckeri causes yersiniosis, also known as enteric redmouth disease, predominantly in farmed

Pan-genome survey of the fish pathogen Yersinia ruckeri links accessory- and amplified genes to virulence

“…This includes CC2 found globally in rainbow trout [ 12 ], CC5 from Australian salmon [ 7 ] as well as those of non-O1 serotypes such as strains BigCreek74 and SC09. Lineage A also contains all disease-associated Norwegian isolates, belonging respectively to the currently dominating CC1 and to CC10 from the late 1980s [ 1 , 18 ], as well as the mildly virulent CC3 (serotype O2). Two notable exceptions to the association between virulence and affiliation to lineage A are CC7 and CC9, which in Norway are associated with biofilms in salmon rearing facilities and egg-fluid of apparently healthy salmon.…”

“…SDS phenotype was assessed on TSA agar plates with 1% SDS prepared according to Furones, Gilpin & Munn [ 33 ], with colonies surrounded by crystalline deposits after 48h incubation at 22°C interpreted as a positive result. MLVA typing was performed according to Gulla, Mohammad & Colquhoun [ 76 ] or data derived from previous work [ 12 , 18 ]. Serotypes were derived from previously published data or typed using in-house polyclonal rabbit antisera for Yersinia ruckeri O1, O2 and O5 with the slide agglutination technique.…”

qPCR screening for Yersinia ruckeri clonal complex 1 against a background of putatively avirulent strains in Norwegian aquaculture

“…Species verification was performed with MALDI‐TOF (Biotyper Microflex LT; Bruker Daltonics). Isolates of uncertain taxonomic status were classified and confirmed as non‐ Y. ruckeri by whole‐genome‐based analyses (Figure S1) as described previously (Riborg et al, 2022). For spiking experiments, Y. ruckeri CC1 strain NVI‐10705 was cultured in Tryptic Soy Broth at 22°C with shaking until mid‐log phase, from which a dilution series was prepared with sterile phosphate‐buffered saline (PBS) chilled on ice and enumerated by plating on 5% bovine blood agar (BA) in triplicate.…”

“…The CC1‐specific locus was identified by alignment of genomes in Mauve (development version 20,150,226) (Darling et al, 2010), comparing Y. ruckeri CC1 and non‐CC1 MlVA genotypes identified previously (Riborg et al, 2022), followed by BLAST searches (Altschul et al, 1997) on local and public databases with candidate sequences to identify CC1‐specific targets suitable for PCR analysis. An intergenic region between the class C beta‐lactamase (acc.…”

“…Isolates of uncertain taxonomic status were classified and confirmed as non-Y. ruckeri by whole-genome-based analyses (Figure S1) as described previously (Riborg et al, 2022).For spiking experiments, Y. ruckeri CC1 strain NVI-10705 was cultured in Tryptic Soy Broth at 22°C with shaking until mid-log phase, from which a dilution series was prepared with sterile phosphate-buffered saline (PBS) chilled on ice and enumerated by plating on 5% bovine blood agar (BA) in triplicate. For the challenge trials, Y. ruckeri NVI-10705 was grown in Brain Heart Infusion Broth at 15°C with shaking for 20 hr, harvested by centrifugation and re-suspension in PBS, followed by enumeration on a cell counter (Casy Inovatis; Roche Diagnostics) and by plating of a 10-fold dilution series on BA.…”