Molecular typing divides marine mammal strains of Brucella into at least three groups with distinct host preferences

Abstract

In order to investigate the genetic relationships within Brucella isolated from marine mammals, two genome-based typing methods, variable number of tandem repeats (VNTR) typing and multilocus sequence analysis (MLSA), were applied to a selection of 74 marine mammal isolates. All isolates were examined by VNTR and data were compared with multilocus sequencing data from a subset of 48 of these. Marine mammal brucellae are distinct from classically recognized species by these methods and appear to correspond to three major genetic groups, which reflect distinct preferred hosts. One group contains isolates predominantly found in pinnipeds (seals) and corresponds to the previously proposed species 'Brucella pinnipediae'. However, isolates corresponding to the previously proposed species 'Brucella cetaceae' fall into two distinct groups that appear to have different preferred cetacean hosts (porpoises and dolphins). Furthermore, these two groups appear less closely related to each other than either group is to 'B. pinnipediae' isolates. The groups identified by VNTR typing and MLSA are completely congruent. The relevance of these findings to current proposals to recognize two species of marine mammal Brucella is discussed. INTRODUCTIONThe genus Brucella contains Gram-negative, facultatively intracellular pathogens that can infect many species of animals of economic importance, such as cattle, sheep, goats and pigs . Humans usually become infected through ingestion of unpasteurized dairy products or via occupational activities such as veterinary work, farming and butchery. Whilst animal brucellosis can present few symptoms and infection is often only recognized on abortion, in humans the disease causes flulike symptoms, including recurrent fever, chills, night sweats and nausea, as well as chronic fatigue and depression if the infection is not cleared early.Brucella can also infect wild animals (Davis, 1990), and in recent years it has also been isolated from various marine mammal species. In 1994, two reports described the first isolation of Brucella from marine mammals. These strains originated from four common seals (Phoca vitulina), two harbour porpoises (Phocoena phocoena) and a common dolphin (Delphinus delphis) in Scotland (Ross et al., 1994), and a captive bottlenose dolphin (Tursiops truncatus) in California, USA (Ewalt et al., 1994). Since these initial isolations, marine mammal Brucella have been isolated from a range of animals, including Atlantic white-sided dolphins (Lagenorhynchus acutus), striped dolphins (Stenella coeuleoalba), grey seals (Halichoerus grypus), hooded seals (Cystophora cristata), European otters (Lutra lutra) (Foster et al., 1996), Pacific harbour seals (Phoca vitulina richardsi) (Garner et al., 1997), minke whales (Balaenoptera acutorostrata) (Clavareau et al., 1998), harp seals (Phoca groenlandica), ringed seals (Phoca hispida) (Forbes et al., 2000) and whitebeaked dolphins (Lagenorhynchus albirostris) (Foster et al., 2002).Six Brucella species are currently recognized based on pheno...

Marine MammalBrucellaGenotype Associated with Zoonotic Infection

“…When comparing profi les at 6 loci with a relatively slow evolutionary speed, previously shown to be useful for dividing Brucella isolates into species groups (8), we determined that F5/99 and the 3 naturally acquired human isolates share a unique profi le not seen in any of >1,400 isolates of marine or terrestrial Brucella species examined to date. In contrast, the strain associated with laboratory-acquired infection (4) was not a member of ST27 but belonged to ST23, a genotype that is predominantly associated with porpoises (9).…”

A multiplex real-time polymerase chain reaction assay with two internal controls for the detection of Brucella species in tissues, blood, and feces from marine mammals

“…11 Other genetic studies support 3 distinct lineages with associated host preferences for pinnipeds, dolphins, and porpoises, although host specificity is not absolute. 13 Information about exposure and disease prevalence in potentially vulnerable marine mammal populations is growing; however, many questions have yet to be answered, including the specifics of transmission, pathogenicity, and susceptibility.…”

Epidemiologic Relatedness between Brucella abortus Isolates from Livestock and Wildlife in South Korea

“…Some investigators reported that MLVA could classify Brucella isolates in accordance with different host origin (Groussaud et al, 2007), geographic region (Kattar et al, 2008), and species (Whatmore et al, 2006). In clustering and traceback analysis, B. abortus isolates from wild animals were included in the same group as isolates from livestock, suggesting that direct or indirect horizontal transfer may occur and that brucellosis in wildlife reservoirs may pose a threat to humans and domestic animals.…”

“…The MLVA typing assay has been recommended by many researchers to analyze the genetic diversity and to trace the origins of infection (Whatmore et al, 2006;Al Dahouk et al, 2007;Groussaud et al, 2007;Her et al, 2009;Kang et al, 2009;Abril et al, 2011). Seventeen markers (16 loci and HOOF-3) used previously were available for follow-up (Bricker et al, 2003;Her et al, 2009).…”

“…Because of the high degree of sequence homology (over 90%) among Brucella species (Vizcaíno et al, 2000;Halling et al, 2005), a powerful molecular typing method was required to clarify the epidemiologic relationships among Brucella infections. Multilocus variable-number tandem repeats analysis (MLVA) is useful in tracing the epidemiology of disease outbreaks (Le Flè che et al, 2006;Whatmore et al, 2006;Groussaud et al, 2007;Kattar et al, 2008;Kang et al, 2009;Abril et al, 2011).…”