Isolation of a novel ‘atypical’ Brucella strain from a bluespotted ribbontail ray (Taeniura lymma)

Abstract

A pleomorphic Gram-negative, motile coccobacillus was isolated from the gills of a wild-caught bluespotted ribbontail ray after its sudden death during quarantine. Strain 141012304 was observed to grow aerobically, to be clearly positive for cytochrome oxidase, catalase, urease and was initially identified as "Brucella melitensis" or "Ochrobactrum anthropi" by Matrix-assisted laser desorption/ionization-time of flight mass spectrometry and VITEK2-compact, respectively. Affiliation to the genus Brucella was confirmed by bcsp31 and IS711 PCR as well as by Brucella species-specific multiplex PCR, therein displaying a characteristic banding pattern recently described for Brucella strains obtained from amphibian hosts. Likewise, based on recA sequencing, strain 141012304 was found to form a separate lineage, within the so called 'atypical' Brucella, consisting of genetically more distantly related strains. The closest similarity was detected to brucellae, which have recently been isolated from edible bull frogs. Subsequent next generation genome sequencing and phylogenetic analysis confirmed that the ray strain represents a novel Brucella lineage within the atypical group of Brucella and in vicinity to Brucella inopinata and Brucella strain BO2, both isolated from human patients. This is the first report of a natural Brucella infection in a saltwater fish extending the host range of this medically important genus.

The role of ‘atypical’Brucellain amphibians: are we facing novel emerging pathogens?

“…At that time, bacterial isolates were identified by API 20NE as Ochrobactrum anthropi , while recent genetic analyses clearly demonstrated that they belong into the ‘atypical’ Brucella group (Eisenberg et al . ).…”

“…Beside isolates that are very similar and with respect to recA gene sequences indistinguishable from B. inopinata , four additional novel clusters exist within the extended Brucella group (Eisenberg et al . , Scholz et al . unpublished).…”

“…All isolates represent novel members of the ‘atypical’ Brucella group (Eisenberg et al . ). Furthermore, six isolates associated with spinal arthropathy in free‐ranging cane toads in Australia (Shilton et al .…”

“…) and formerly identified as Ochrobactrum were taxonomically reclassified as novel ‘atypical’ Brucella by recent genetic analyses (Eisenberg et al . ). Further evidence exists that brucellae from amphibian hosts are much more common than previously thought (Fischer et al .…”

Extended Multilocus Sequence Analysis to Describe the Global Population Structure of the Genus Brucella: Phylogeography and Relationship to Biovars

“…These groups are often described as “atypical” in the literature reflecting their genetic separation from classical species. A number of other isolates that await formal taxonomic description originating from sources as diverse as humans, frogs, fish, and additional rodents will likely extend diversity within both the classical group and newly emerging “atypical” Brucella in the near future (Tiller et al, 2010a,b; Godfroid et al, 2011; Eisenberg et al, 2012; Scholz and Vergnaud, 2013; Whatmore et al, 2015; Eisenberg et al, 2016). …”