Characterization of Novel Brucella Strains Originating from Wild Native Rodent Species in North Queensland, Australia

Abstract

We report on the characterization of a group of seven novel Brucella strains isolated in 1964 from three native rodent species in North Queensland, Australia, during a survey of wild animals. The strains were initially reported to be Brucella suis biovar 3 on the basis of microbiological test results. Our results indicated that the rodent strains had microbiological traits distinct from those of B. suis biovar 3 and all other Brucella spp. To reinvestigate these rodent strains, we sequenced the 16S rRNA, recA, and rpoB genes and nine housekeeping genes and also performed multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA). The rodent strains have a unique 16S rRNA gene sequence compared to the sequences of the classical Brucella spp. Sequence analysis of the recA, rpoB, and nine housekeeping genes reveals that the rodent strains are genetically identical to each other at these loci and divergent from any of the currently described Brucella sequence types. However, all seven of the rodent strains do exhibit distinctive allelic MLVA profiles, although none demonstrated an amplicon for VNTR 07, whereas the other Brucella spp. did. Phylogenetic analysis of the MLVA data reveals that the rodent strains form a distinct clade separate from the classical Brucella spp. Furthermore, whole-genome sequence comparison using the maximal unique exact matches index (MUMi) demonstrated a high degree of relatedness of one of the seven rodent Brucella strains (strain NF 2653) to another Australian rodent Brucella strain (strain 83-13). Our findings strongly suggest that this group of Brucella strains isolated from wild Australian rodents defines a new species in the Brucella genus.Brucella species are facultative intracellular Gram-negative members of the Alphaproteobacteria class capable of causing brucellosis in a range of animal hosts, including domesticated livestock, wildlife, marine mammals, and humans (1,5,7,29,32,33,36,47). Brucellosis is the most prevalent zoonotic disease worldwide, causing spontaneous abortion and fetal death in animals and severe flu-like symptoms, focal complications, and often, chronic disease in humans (7,11,22,27,40,41,49,50). Brucella species are typically transmitted to humans through consumption of unpasteurized dairy products or exposure to fluids or tissues from infected animals (45, 49). Animals are primary hosts of all Brucella spp., which include Brucella abortus (cattle), B. canis (dogs), B. melitensis (goats, cows, and sheep), B. suis (swine), B. ovis (rams), and B. neotomae (desert rats) (3,7,8). Recently, three additional Brucella species have been recognized: B. pinnipedialis (seals), B. ceti (dolphins) (5), and B. microti. B. microti was initially isolated from the common vole in the Czech Republic (33, 35). In the mid-1980s, DNA-DNA hybridization studies demonstrated a very high level of genetic similarity (98.5%) among the Brucella spp., which led to the adoption of a monospecies concept for the Brucella genus, with all the species at that time renamed as biovars of ...

Brucellosis at the animal/ecosystem/human interface at the beginning of the 21st century

“…The use of multilocus sequence analysis (MLSA) opens the way to detailed characterization of the global population structure of Brucella (Whatmore et al, 2007). These analyses confirmed the status of the classical species as distinct genetic entities, began to index intra-species diversity and relate this to historical biovar designations, and provided a framework for the placement of atypical or emerging Brucella isolates Schlabritz-Loutsevitch et al, 2009;Tiller et al, 2010). Further, these analyses and the availability of more robust phylogenetic histories, allowed the identification of canonical single nucleotide polymorphisms (SNPs) that could be exploited as the basis of rapid diagnostic tests.…”

“…To date the genus Brucella consists thus of 10 species. Prospective Brucella species have also been isolated from three native rat species in Australia, but not yet been included in the genus (Tiller et al, 2010) as well as in association with two cases of stillbirth in non-human primates (Schlabritz-Loutsevitch et al, 2009). The preferential hosts and the pathogenicity for humans of the 10 recognized Brucella species are depicted in Table 1.…”

Brucella vulpis sp. nov., isolated from mandibular lymph nodes of red foxes (Vulpes vulpes)

“…Within the last few years, potential novel species of Brucella have been isolated from various sources, including rodents (Tiller et al, 2010), different frog species (Eisenberg et al, 2012;Fischer et al, 2012;Whatmore et al, 2015), red foxes (Hofer et al, 2012) and a blue dotted ray (T. Eisenberg and H. C. Scholz, unpublished data), and are awaiting final genus affiliation. Although genome similarities of these potential novel species of Brucella are still above 90 % compared with classical species (Wattam et al, 2009;this study), the majority of these novel candidates carries genetic information not found in classical species but similar to genetic information found in other soil-living bacteria, such as Ochrobactrum, Paracoccus denitrificans, Agrobacterium and Sinorhizobium.…”

Comparisons of brucellosis between human and veterinary medicine

“…Zoonotic potential is classified as pathogenicity and virulence in human hosts. Original citation indicates the original publication where the species was characterized.SpeciesNatural hostZoonotic Potential [8]Original Citation B. melitensis Sheep, goats, and camelsYes – High[5] B. abortus Cattle, elk, and bisonYes – High[6] B. suis Pigs, hare, reindeer/caribouYes – High[122] B. canis Dogs (domestic and wild)Yes – Moderate[123] B. ovis SheepNo reported infections[124] B. neotomae Desert wood ratsNo reported infections[125] B. ceti CetaceansYes – Low[126] B. pinnipedialis PinnipedsYes – Low B. microti Red foxes and common volesNo reported infections[127] B. inopinata UnknownYes – High[2,128] B. papionis Non-Human PrimatesNo reported infections[129,130] B. vulpis Red foxNo reported infections[131,132] Brucella NFXXXX Australian ratNo reported infections[133,134]…”