Characterisation of North American Brucella isolates from marine mammals

[Zoonotic potential of brucellosis in marine mammals]

Introduction

Brucellosis in marine mammals (cetacean and pinnipeds) has emerged in a very significant way during the last two decades. Currently Brucella ceti and Brucella pinnipedialis are the two recognized species in marine mammals, but available information is still limited. Several genotypes have been identified, and studies on the relationship between sequence type (ST) and organ pathogenicity or tropism have indicated differences in pathogenesis between B. ceti sequences in cetaceans. The zoonotic potential of this disease is based on the identification of the main sources of introduction and spread of Brucella spp. in the marine environment as well as on the factors of exposure of marine mammals and humans to the bacteria.

Bibliographic review

This article is a bibliographical review on marine mammal brucellosis, including the features, sources and transmission modes of each Brucella species, as well as their potential pathogenicity in animals and humans.

Conclusion

Different genotypes of marine Brucella spp have been isolated from marine mammal species but without any evidence of pathology induced by these bacteria. Associated lesions are variable and include subcutaneous abscesses, meningo-encephalomyelitis, pneumonia, myocarditis, osteoarthritis, orchitis, endometritis, placentitis and abortion. The isolation of marine B. spp from marine mammal respiratory parasites associated to lung injury has raised the intriguing possibility that they may serve as a vector for the transmission of this bacterium.The severity of marine B. spp remains unknown due to the lack of an estimate of the prevalence of this disease in marine mammals. The number of suspected human cases is still very limited. However, by analogy with other germs of the genus Brucella responsible for abortion in ruminants and for a febrile and painful state in human beings, prevention measures are essential. The significant increase in the number of strandings coupled with a high seroprevalence in certain species of marine mammals must be considered for people in direct or indirect contact with these animals. Ongoing epidemiological monitoring combined with extensive post-mortem examinations (necropsy, bacteriology and sequencing) of all species of stranded marine mammals would deepen knowledge on the zoonotic potential of marine Brucella species.

Brucella infection in rough-toothed dolphin (Steno bredanensis) with severe orchitis stranded on the Pacific coast of Japan

In the western North Pacific, prominent granulomatous testes have been detected in many Brucella-infected common minke whales (Balaenoptera acutorostrata), but there have been no reports in toothed cetaceans. We found severe orchitis with granulomatous lesions in a rough-toothed dolphin (Steno bredanensis) stranded on the Pacific coast of Japan in 2011. Histopathological examination revealed leukocyte infiltration of the lesions. DNA from the lesion was analyzed by PCR and it showed molecular biological similarities with those of Brucella-infected common minke whales and Brucella ceti of sequence-type 27 (ST27). These results suggest that the type of Brucella ceti that infected the dolphin was ST27, which may have caused severe orchitis. This study adds to our understanding of Brucella infections in marine mammals.

New insights into the pathogenesis and transmission of Brucella pinnipedialis: systemic infection in two bottlenose dolphins (Tursiops truncatus)

IMPORTANCE

Brucella spp. are zoonotic pathogens that can affect both terrestrial and marine mammals. Brucella ceti has been identified in various cetacean species, but only one sequence type (ST27) has been reported in humans. However, it is important to conduct surveillance studies to better understand the impact of marine Brucella species on marine mammals, a typically understudied host group. Here, we describe a systemic infection by two related strains of Brucella pinnipedialis (ST25) in a couple of live-stranded bottlenose dolphins, with more severe lesions in the younger animal. Furthermore, B. pinnipedialis was first detected in milk from a female cetacean that stranded with its offspring. Our study reveals novel insights into the epidemiology and pathological consequences of B. pinnipedialis infections in cetaceans, emphasizing the crucial importance of ongoing surveillance and accurate diagnosis to understand the impact of this pathogen on marine mammal populations.

Brucella ceti Infection in Striped Dolphins from Italian Seas: Associated Lesions and Epidemiological Data

Brucella ceti infections have been increasingly reported in cetaceans. In this study, we analyzed all cases of B. ceti infection detected in striped dolphins stranded along the Italian coastline between 2012 and 2021 (N = 24). We focused on the pathogenic role of B. ceti through detailed pathological studies, and ad hoc microbiological, biomolecular, and serological investigations, coupled with a comparative genomic analysis of the strains. Neurobrucellosis was observed in 20 animals. The primary histopathologic features included non-suppurative meningoencephalitis (N = 9), meningitis (N = 6), and meningoencephalomyelitis (N = 5), which was also associated with typical lesions in other tissues (N = 8). Co-infections were detected in more than half of the cases, mostly involving Cetacean Morbillivirus (CeMV). The 24 B. ceti isolates were assigned primarily to sequence type 26 (ST26) (N = 21) and, in a few cases, ST49 (N = 3). The multilocus sequence typing (cgMLST) based on whole genome sequencing (WGS) data showed that strains from Italy clustered into four genetically distinct clades. Plotting these clades onto a geographic map suggests a link between their phylogeny and the topographical distribution. These results support the role of B. ceti as a primary neurotropic pathogen for striped dolphins and highlight the utility of WGS data in understanding the evolution of this emerging pathogen.

Pathogen Exposure in White Whales (Delphinapterus leucas) in Svalbard, Norway

The Svalbard white whale (Delphinapterus leucas) population is one of the smallest in the world, making it particularly vulnerable to challenges such as climate change and pathogens. In this study, serum samples from live captured (2001−2016) white whales from this region were investigated for influenza A virus (IAV) antibodies (Abs) (n = 27) and RNA (n = 25); morbillivirus (MV) Abs (n = 3) and RNA (n = 25); Brucella spp. Abs; and Toxoplasma gondii Abs (n = 27). IAV Abs were found in a single adult male that was captured in Van Mijenfjorden in 2001, although no IAV RNA was detected. Brucella spp. Abs were found in 59% of the sample group (16/27). All MV and T. gondii results were negative. The results show that Svalbard white whales have been exposed to IAV and Brucella spp., although evidence of disease is lacking. However, dramatic changes in climate and marine ecosystems are taking place in the Arctic, so surveillance of health parameters, including pathogens, is critical for tracking changes in the status of this vulnerable population.

Brucella ceti and Brucella pinnipedialis genome characterization unveils genetic features that highlight their zoonotic potential

The Gram-negative bacteria Brucella ceti and Brucella pinnipedialis circulate in marine environments primarily infecting marine mammals, where they cause an often-fatal disease named brucellosis. The increase of brucellosis among several species of cetaceans and pinnipeds, together with the report of sporadic human infections, raises concerns about the zoonotic potential of these pathogens on a large scale and may pose a threat to coastal communities worldwide. Therefore, the characterization of the B. ceti and B. pinnipedialis genetic features is a priority to better understand the pathological factors that may impact global health. Moreover, an in-depth functional analysis of the B. ceti and B. pinnipedialis genome in the context of virulence and pathogenesis was not undertaken so far. Within this picture, here we present the comparative whole-genome characterization of all B. ceti and B. pinnipedialis genomes available in public resources, uncovering a collection of genetic tools possessed by these aquatic bacterial species compared to their zoonotic terrestrial relatives. We show that B. ceti and B. pinnipedialis genomes display a wide host-range infection capability and a polyphyletic phylogeny within the genus, showing a genomic structure that fits the canonical definition of closeness. Functional genome annotation led to identifying genes related to several pathways involved in mechanisms of infection, others conferring pan-susceptibility to antimicrobials and a set of virulence genes that highlight the similarity of B. ceti and B. pinnipedialis genotypes to those of Brucella spp. displaying human-infecting phenotypes.

Serological Detection of Marine Origin Brucella Exposure in Two Alaska Beluga Stocks

Simple Summary

Brucellosis, the disease caused by Brucella bacteria, is of emerging concern in marine-mammal populations worldwide due to its potential link to reproductive failure, yet is less well-studied than in terrestrial animals, such as cattle. To understand Brucella exposure and disease in two populations of beluga, in Bristol Bay and the eastern Chukchi Sea, Alaska, USA, this study screened animals for the presence of antibodies against the bacterium (serology), as well as tested for the direct presence of bacterial DNA or bacterial growth from tissue samples. More than half of all animals tested, from both populations, were positive for the presence of antibodies, providing evidence of exposure to Brucella. Few animals, however, were positive for the direct detection of Brucella DNA and none resulted in successful bacterial growth, suggesting a lack of active clinical disease. The high rate of exposure in these populations supports the need for long-term monitoring of beluga populations, particular those that are threatened or endangered, such as the Cook Inlet belugas.

Abstract

Among emerging threats to the Arctic is the introduction, spread, or resurgence of disease. Marine brucellosis is an emerging disease concern among free-ranging cetaceans and is less well-studied than terrestrial forms. To investigate marine-origin Brucella sp. exposure in two beluga stocks in Alaska, USA, this study used serological status as well as real-time polymerase chain reaction (rtPCR) and bacterial culture. In total, 55 live-captured–released belugas were tested for Brucella exposure in Bristol Bay (2008–2016) and 112 (8 live-captured; 104 subsistence-harvested) whales were tested in the eastern Chukchi Sea (2007–2017). In total, 73% percent of Bristol Bay live captures, 50% of Chukchi Sea live captures, and 66% of Chukchi Sea harvested belugas were positive on serology. Only 10 of 69 seropositive belugas were rtPCR positive in at least one tissue. Only one seropositive animal was PCR positive in both the spleen and mesenteric lymph node. All animals tested were culture negative. The high prevalence of seropositivity detected suggests widespread exposure in both stocks, however, the low level of rtPCR and culture positive results suggests clinical brucellosis was not prevalent in the belugas surveyed. Continued detection of Brucella exposure supports the need for long-term monitoring of these and other beluga populations.

Brucella ceti sequence type 23, 26, and 27 infections in North American cetaceans

Brucella ceti infection is associated with a variety of disease outcomes in cetaceans globally. Multiple genotypes of B. ceti have been identified. This retrospective aimed to determine if specific lesions were associated with different B. ceti DNA sequence types (STs). Characterization of ST was performed on 163 samples from 88 free-ranging cetaceans, including common bottlenose dolphin Tursiops truncatus (T.t.; n = 73), common short-beaked dolphin Delphinus delphis (D.d.; n = 7), striped dolphin Stenella coeruleoalba (n = 3), Pacific white-sided dolphin Lagenorhynchus obliquidens (n = 2), sperm whale Physeter macrocephalus (n = 2), and harbour porpoise Phocoena phocoena (n = 1), that stranded along the coast of the US mainland and Hawaii. ST was determined using a previously described insertion sequence 711 quantitative PCR. Concordance with 9-locus multi-locus sequence typing was assessed in a subset of samples (n = 18). ST 26 was most commonly identified in adult dolphins along the US east coast with non-suppurative meningoencephalitis (p = 0.009). Animals infected with ST 27 were predominately perinates that were aborted or died shortly after birth with evidence of in utero pneumonia (p = 0.035). Reproductive tract inflammation and meningoencephalitis were also observed in adult T.t. and D.d. with ST 27, though low sample size limited interpretation. ST 23 infections can cause disease in cetacean families other than porpoises (Phocoenidae), including neurobrucellosis in D.d. In total, 11 animals were potentially infected with multiple STs. These data indicate differences in pathogenesis among B. ceti STs in free-ranging cetaceans, and infection with multiple STs is possible.

Anti-Brucella antibodies in seals at coastal locations of Hokkaido, Japan, with focus on life stages

The enzyme-linked immunosorbent assay (ELISA) was applied to detect antibodies against Brucella abortus in serum samples from four seal species at nine coastal locations of Hokkaido, Japan. These antibodies were detected in 27% (32/118) of Western Pacific harbor seals (Phoca vitulina stejnegeri) at Cape Erimo. The antibodies were observed in spotted seals (P. largha) in one out of six at Nemuro, in two out of three at Rebun Island, in one out of two at Bakkai, and in examined one at Soya. They were also found in respective examined one ribbon seal (Histriophoca fasciata) and one ringed seal (Pusa hispida) at Akkeshi. Harbor seals that tested positive were mostly yearlings (35%, 20/57) and juveniles (45%, 10/22), while only one pup (1/13) and one subadult (1/5) tested positive with low titers of the antibody; no antibodies were observed in adults (n=21). These results suggest that Brucella mainly infected harbor seals from the environment while weaning, and the bacteria were cleared during the early life stage of the seals. In spotted seals, however, antibodies were also detected in adults, suggesting that spotted seals could become infected with Brucella even as adults. It is also possible that a different, more persistent strain of Brucella may have infected the spotted seals.

Brucella Infection Investigation in Cetaceans and Manatees in Northeast Brazil

Among the bacterial infections that impair the health status of marine mammals, those caused by Brucella spp. are the most reported worldwide. Brucella infections in marine mammals can result in acute or chronic disease and are associated with variable clinical outcomes, depending on the organ involved during the infectious process, infection route, host immunity, and strain pathogenicity. Asymptomatic infections may also occur. The current study expands the investigation of Brucella infection in northeast Brazil by analyzing 19 dead, stranded cetaceans and 52 Antillean manatees Trichechus manatus manatus. The manatees included 8 dead, captive manatees and 44 live specimens, of which 10 were analyzed only after reintroduction into the wild as part of a rehabilitation program, 9 were analyzed both while in captivity or semi-captivity and after reintroduction, 20 were sampled only in captivity or semi-captivity, and 5 were free-living manatees. Serological tests were used to screen for antibodies against smooth Brucella spp. Whole blood, swabs, and tissue samples were screened for Brucella spp. DNA by PCR. Samples with positive PCR results were cultured for Brucella spp. isolation. All manatees yielded negative results in serological and molecular tests. Brucella spp. DNA was detected in the kidney of one adult Guiana dolphin Sotalia guianensis exhibiting necrosis in the liver. No growth of Brucella spp. was observed via microbiological culturing. This study is the first report of Brucella spp. DNA detection in cetaceans in the state of Pernambuco, and it highlights the importance of conducting systematic monitoring for the presence of Brucella infection in marine mammals along the Brazilian coast, especially in the northeast region, where several cases have been reported.

First confirmed reports of the isolation of Brucella ceti from a Risso's dolphin Grampus griseus and a killer whale Orcinus orca

Brucella ceti has been recovered from a number species of cetaceans worldwide over the last 25 yr. Here we report, for the first time, the recovery of B. ceti from a Risso's dolphin Grampus griseus and a killer whale Orcinus orca. Recovery from an abdominal mass in the dolphin provides further evidence of the systemic pathogenic potential for B. ceti infection in cetaceans. The isolation of B. ceti ST23 (porpoise cluster) from a killer whale from a group known to eat other marine mammals raises the possibility of infection via ingestion. This report takes the number of cetacean species in UK coastal waters from which B. ceti has been isolated to 11 and highlights the value of routine, comprehensive and specific screening for significant pathogens such as Brucella sp. by strandings networks.

Brucella sp. sequence-type 27 associated with abortion in dwarf sperm whale Kogia sima

A dwarf sperm whale Kogia sima stranded alive along the Central Pacific Coast of Costa Rica. The whale, handled by tourists and local inhabitants, was weak, had buoyancy difficulties, and eventually aborted and died, showing severe necrotizing placentitis and other pathological signs. Both the mother and the fetus had antibodies against Brucella lipopolysaccharide. Brucella organisms were isolated from various tissues of both animals and were characterized. The bacterium genome corresponded to sequence-type 27 (ST27) and clustered together with other Brucella ST27 isolated in humans and cetaceans.

Meningoencephalitis in a common minke whale Balaenoptera acutorostrata associated with Brucella pinnipedialis and gamma-herpesvirus infection

Fatal marine Brucella infections with histologic lesions specific to the central nervous system (CNS), known as neurobrucellosis, have been described in 5 species of odontocete cetaceans in the UK: striped dolphins Stenella coeruleoalba, Atlantic white-sided dolphins Lagenorhynchus acutus, short-beaked common dolphins Delphinus delphis, long-finned pilot whale Globicephala melas and Sowerby's beaked whale Mesoplodon bidens. To date, these CNS lesions have only been associated with Brucella ceti ST26 and not with B. pinnipedialis, which is rarely isolated from cetaceans and, although commonly found in various seal species, has never been associated with any pathology. This paper describes the first report of neurobrucellosis in a common minke whale Balaenoptera acutorostrata which was associated with the isolation of Brucella pinnipedialis ST24 and co-infection with Balaenoptera acutorostrata gamma-herpesvirus 2. This is the first report of neurobrucellosis in any species of mysticete and the first report of Brucella pinnipedialis in association with any pathology in any species of marine mammal, which may be due to co-infection with a herpesvirus, as these are known to be associated with immunosuppression.

Emerging diversity and ongoing expansion of the genus Brucella

Remarkable genetic diversity and breadth of host species has been uncovered in the Brucella genus over the past decade, fundamentally changing our concept of what it means to be a Brucella. From ocean fishes and marine mammals, to pond dwelling amphibians, forest foxes, desert rodents, and cave-dwelling bats, Brucella have revealed a variety of previously unknown niches. Classical microbiological techniques have been able to help us classify many of these new strains but at times have limited our ability to see the true relationships among or within species. The closest relatives of Brucella are soil bacteria and the adaptations of Brucella spp. to live intracellularly suggest that the genus has evolved to live in vertebrate hosts. Several recently discovered species appear to have phenotypes that are intermediate between soil bacteria and core Brucella, suggesting that they may represent ancestral traits that were subsequently lost in the traditional species. Remarkably, the broad relationships among Brucella species using a variety of sequence and fragment-based approaches have been upheld when using comparative genomics with whole genomes. Nonetheless, genomes are required for fine-scale resolution of many of the relationships and for understanding the evolutionary history of the genus. We expect that the coming decades will reveal many more hosts and previously unknown diversity in a wide range of environments.

Serological screening for Brucella spp. and Leptospira spp. antibodies in southern elephant seals Mirounga leonina from Elephant Island, Antarctica, in 2003 and 2004

Brucella spp. and Leptospira spp. antibodies were surveyed in 35 southern elephant seals (SESs) Mirounga leonina at Elephant Island (South Shetland Islands), western Antarctic peninsula, in the Austral summer of 2003 and 2004. The rose Bengal test and a commercial competitive ELISA (c-ELISA) were used to detect Brucella spp. exposure, and the microscopic agglutination test (MAT) with 22 live serovars was used to determine anti-Leptospira spp. antibodies. We found evidence of Brucella spp. exposure in 3 of 35 (8.6%) SESs tested via the c-ELISA displaying high percentage inhibition (PI), similar to other studies in pinnipeds in which Brucella spp. antibodies have been determined. Two of the 3 positives were pups (PI = 70.4 and 86.6%), while the third was an adult female (PI = 48.8%). The 3 c-ELISA positive SESs were additionally tested via the serum agglutination test but were found to be negative. All individuals were negative for antibodies against 22 Leptospira spp. serovars by MAT. These results contribute to the knowledge and monitoring of zoonotic pathogens with epizootic potential in Southern Ocean pinnipeds. Given the potential impact that pathogens may have on the abundance of wild (sometimes threatened and endangered) populations, constant monitoring and surveillance are required to prevent pathogen spread, particularly under forecast climate change scenarios.

Neurobrucellosis due to Brucella ceti ST26 in Three Sowerby's Beaked Whales (Mesoplodon bidens)

Fatal meningoencephalitis due to Brucella ceti infection has been described in striped dolphins (Stenella coeruleoalba), Atlantic white-sided dolphins (Lagenorhynchus acutus), short-beaked common dolphins (Delphinus delphis) and long-finned pilot whales (Globicephala melas), which are all within the family Delphinidae. We report B. ceti-associated neurobrucellosis in three juvenile male Sowerby's beaked whales (Mesoplodon bidens) that all had typical lesions of lymphocytic meningoencephalitis, which increased in severity from rostral to caudal regions of the brain. In two cases there was loss of ependymal cells lining the cerebral ventricular system, with large numbers of lymphocytes in the underlying neuropil. This finding suggests that B. ceti gains access to, and multiplies in, the cerebrospinal fluid, and confirms that this is the sample of choice for bacteriological recovery of the causative organism. These findings expand the increasing range of cetaceans susceptible to neurobrucellosis to members of the family Ziphiidae.

Draft Genome Sequence of Brucella ceti Isolated in the Western Pacific Ocean

In 2018, Brucella ceti was isolated from a bottlenose dolphin from the western Pacific Ocean. Here, we report a draft genome sequence of the isolate BD1442 of sequence type 27, which is the only sequence type known to have been isolated from human clinical cases.

In 2018, Brucella ceti was isolated from a bottlenose dolphin from the western Pacific Ocean. Here, we report a draft genome sequence of the isolate BD1442 of sequence type 27, which is the only sequence type known to have been isolated from human clinical cases.

Molecular characterization of Brucella ceti from a bottlenose dolphin (Tursiops truncatus) with osteomyelitis in the western Pacific

Although the presence of Brucella spp. in the western Pacific has been suggested by epidemiological studies on cetaceans, it has not been confirmed by bacterial isolation. Here, for the first time, we report that a marine Brucella strain was isolated in the western Pacific from a bottlenose dolphin with osteomyelitis. The isolate from the lesion was confirmed to be B. ceti of sequence type 27 by multilocus sequence typing and Bruce-ladder PCR. Infrequent-restriction-site PCR and omp2 gene sequencing revealed that molecular characteristics of this isolate were similar to those of Brucella DNA previously detected from minke whales in the western North Pacific. These results suggest that genetically related Brucella strains circulate in cetacean species in this region.

Detection of Brucella ceti in Two Indo-Pacific Finless Porpoises (Neophocaena Phocaenoides) Stranded in Hong Kong

Brucella ceti has been detected in several species of free-ranging odontocetes, in several geographic areas but it has not been reported in Indo-Pacific finless porpoises (Neophocaena phocaenoides) nor in any odontocetes in waters in the South China Sea. Sampling of odontocetes stranded in Hong Kong Special Administrative Region, People's Republic of China, was carried out as part of a stranding monitoring program to evaluate the pathogens harbored by these threatened species. A real-time PCR method targeting the Brucella genus-specific 31kDa Brucella cell surface salt extractable (bcsp31) gene, gene sequencing, and phylogenetic characterisation produced three PCR products of the expected size and sequence, from two stranded Indo-Pacific finless porpoises. The PCR products were obtained from brain tissue from of a neonate and from mammary fluid from a sexually mature female. Further testing for this pathogen should be performed to determine whether Brucella ceti might have a detrimental effect on reproduction and calf survival in Indo-Pacific finless porpoises and pose a threat to the conservation of this species. The importance of biosafety and biosecurity measures when handling cetaceans or their tissues and products in the South China Sea is also highlighted.

Brucellosis associated with stillbirth in a bottlenose dolphin in Australia

A captive adult female bottlenose dolphin presented with stillbirth. The placenta appeared oedematous. No other gross lesions were evident in the placenta or the stillborn calf. Histopathology revealed mild multifocal placentitis and foetal encephalitis. Brucella sp. was isolated from lung, liver, spleen and kidney. Sequence and phylogenetic analysis demonstrated this organism to be most similar to Brucella ceti sequence type (ST) 27. Brucella sp. DNA was detected in formalin-fixed paraffin-embedded placenta and brain by real-time PCR using primers targeting the IS711 gene. Immunohistochemical staining revealed Brucella sp. antigen in placental inflammation. This is the first report of isolation of Brucella sp. from a marine mammal in the Southern Hemisphere and the first report of marine Brucella-associated disease in Australia.

Pathological findings and survey for pathogens associated with reproductive failure in perinatal Steller sea lions Eumetopias jubatus

Steller sea lions (SSLs) Eumetopias jubatus experienced a population decline in the 1960s, leading to the listing of the western stock as endangered and the eastern stock as threatened under the US Endangered Species Act. A decrease of births in the western stock beginning in the late 1960s indicates that reproductive failure may have contributed to the decline. We evaluated the role pathogens play in spontaneous abortions, premature births and neonatal deaths in SSLs. Archived tissues from carcasses (n = 19) collected in Alaska from 2002 to 2015 were tested by PCR for Coxiella burnetii, Brucella spp., Chlamydia and morbilliviruses. Animals examined included 47% premature pups, 32% aborted fetuses, 11% neonates and 11% intrauterine fetuses. Gross necropsy and histology findings were summarized in the context of the PCR findings. Tissues were negative for Chlamydia and C. burnetii. Brucella spp. were detected in the lung tissues of 3 animals, including 1 positive for the ST27 strain, the first detection of Brucella spp. DNA in SSLs. Phocine distemper virus was detected in 3 animals in 2 skin lesions and 1 placenta by hemi-nested diagnostic qRT-PCR. Both skin and the placental lesions had vesiculoulcerative changes, and 1 skin lesion contained inclusion bodies in syncytia and upon histologic examination, suggesting that the lesions may be associated with an infection reminiscent of phocine distemper virus, the first in SSLs. We highlight the continuing need for disease surveillance programs to improve our understanding of the prevalence and potential population impacts of these infectious disease agents for pinnipeds in Alaskan waters.

Fluorescence signal amplification assay for the detection of B. melitensis 16M, based on peptide-mediated magnetic separation technology and a AuNP-mediated bio-barcode assembled by quantum dot technology

Members of the Brucella spp. are facultative intracellular bacteria that can cause global brucellosis, a zoonotic disease. Herein, a novel fluorescence signal amplification (FSA) method for the rapid detection of B. melitensis 16M was developed based on peptide-mediated magnetic separation (PMS) technology and Au nanoparticle (AuNP)-mediated bio-barcode assay technology assembled by quantum dots (QDs). The PMS technology was used to specifically capture and isolate B. melitensis 16M from food. The immunomagnetic bead-B. melitensis 16M bioconjugates (IMBs-B. melitensis 16M) were then identified by IgY on the surface of AuNPs and the oligonucleotide chains on the surface of the gold nanoparticles were hybridized with bio-barcodes assembled by quantum dots (QD-probe2). The IMB/B. melitensis 16M/IgY-AuNP-probe1/QD-probe2 bioconjugates were concentrated by magnetic separation. Therefore, as the concentration of B. melitensis 16M in the sample increased, the unbound QD-probe2 in the supernatant reduced, and the B. melitensis 16M in the sample could be indirectly measured by detecting the fluorescence in the supernatant. This FSA method can detect B. melitensis 16M concentration in the range of 10 to 106 cfu ml-1 without pre-enrichment, and the limit of detection (LOD) is as low as 10 cfu ml-1 with high specificity. Furthermore, the proposed method for the detection of B. melitensis 16M has a LOD of 1.07 × 102 cfu ml-1 and a linear range from 102 to 107 cfu ml-1 in milk, and a LOD of 1.72 × 102 cfu ml-1, and a linear range from 102 to 106 cfu ml-1 in lamb leach. In addition, this method takes less than 3 h to perform. Thus, the assay that was developed in this study shows promise for rapid, sensitive, and specific detection of B. melitensis 16M.

Molecular, serological, pathological, immunohistochemical and microbiological investigation of Brucella spp. in marine mammals of Brazil reveals new cetacean hosts

Brucella-exposure and infection is increasingly recognized in marine mammals worldwide. To better understand the epidemiology and health impacts of Brucella spp. in marine mammals of Brazil, molecular (conventional PCR and/or real-time PCR), serological (Rose Bengal Test [RBT], Competitive [c]ELISA, Serum Agglutination Test [SAT]), pathological, immunohistochemical (IHC) and/or microbiological investigations were conducted in samples of 129 stranded or by-caught marine mammals (orders Cetartiodactyla [n = 124], Carnivora [n = 4] and Sirenia [n = 1]). Previous serological tests performed on available sera of 27 of the 129 animals (26 cetaceans and one manatee), indicated 10 seropositive cetaceans. Conventional PCR and/or real-time PCR performed in cases with available organs (n = 119) and/or blood or swabs (n = 10) revealed 4/129 (3.1%) Brucella-infected cetaceans (one of them with positive serology; the remaining three with no available sera). Pathological, IHC and/or microbiological analyses conducted in PCR/real-time PCR and/or seropositive cases (n = 13) revealed Brucella-type lesions, including meningitis/meningoencephalitis, pneumonia, necrotizing hepatitis, pericarditis and osteoarthritis in some of those animals, and positive IHC was found in all of them (excepting two live-stranded animals without available organs). Brucella spp. culture attempts were unsuccessful. Our results demonstrated exposure, asymptomatic, acute and chronic Brucella sp. infection in several cetacean species in the Brazilian coast, highlighting the role of this pathogen in stranding and/or death, particularly in Clymene dolphin (Stenella clymene) and short-finned pilot whale (Globicephala macrorhynchus) off Ceará State. Novel hosts susceptible to Brucella included the franciscana (Pontoporia blainvillei), the Guiana dolphin (Sotalia guianensis) and the spinner dolphin (Stenella longirostris). Additionally, three coinfection cases involving Brucella spp. and cetacean morbillivirus, Edwarsiella tarda and Proteus mirabilis were detected. To the best of our knowledge, this is the first long-term and large-scale survey of Brucella spp. in marine mammals of South America, widening the spectrum of susceptible hosts and geographical distribution range of this agent with zoonotic potential.

Isolation and identification of pathogenic Aeromonas veronii from a dead Yangtze finless porpoise

Diseases caused by Aeromonas veronii in freshwater fish have been widely reported, but other species such as aquatic mammals have probably been overlooked. Here, we identified one isolate of A. veronii from a Yangtze finless porpoise Neophocaena asiaeorientalis asiaeorientalis exhibiting disease and mortality, and subsequently confirmed its virulence in artificial infection of BALB/c mice. The bacterial isolate was identified as A. veronii based on physiological, biochemical, and phenotypic features, and homology of the 16S rRNA, cpn60, rpoB, dnaJ and gyrB genes. Our results expand the known host spectrum of A. veronii, which is of great importance for the etiology of porpoise, dolphin, and other cetacean diseases.

Brucella pinnipedialis in lungworms Parafilaroides sp. and Pacific harbor seals Phoca vitulina richardsi: proposed pathogenesis

Brucella spp. were first isolated from marine mammals in 1994 and since have been described in numerous pinniped and cetacean species with nearly global distribution. Microscopic, electron microscopic, or culture results have shown lungworms in harbor seals to be infected with brucellae, suggesting that the lungworms may serve a role in this infection. In this study, we reviewed archived and more recent case material from 5 Pacific harbor seals from Washington State (USA) with evidence of B. pinnipedialis infection in the lungworm Parafilaroides sp. Twenty-two sections of lung containing approximately 220 Parafilaroides sp., stained with an immunohistochemical technique using antibody to B. abortus, showed approximately 80 (36%) infected nematodes. A few brucellae were also present in lung parenchyma in proximity to nematodes. Infection was present in the first- and fourth-stage larvae in the seal lung and intestines, as well as in the male and female reproductive organs of adult nematodes. Infected sperm deposits in the nematode uterus were suggestive of venereal transmission between lungworms. Massive infection of some degenerate adult lungworms and evidence of degeneration of some developing larvae in utero were observed. Based on these observations, we suggest that Parafilaroides sp., rather than the Pacific harbor seal Phoca vitulina richardsi, is the preferred host of B. pinnipedialis infection.

A MALDI-TOF MS database with broad genus coverage for species-level identification of Brucella

Brucella are highly infectious bacterial pathogens responsible for a severely debilitating zoonosis called brucellosis. Half of the human population worldwide is considered to live at risk of exposure, mostly in the poorest rural areas of the world. Prompt diagnosis of brucellosis is essential to prevent complications and to control epidemiology outbreaks, but identification of Brucella isolates may be hampered by the lack of rapid and cost-effective methods. Nowadays, many clinical microbiology laboratories use Matrix-Assisted Laser Desorption Ionization–Time Of Flight mass spectrometry (MALDI-TOF MS) for routine identification. However, lack of reference spectra in the currently commercialized databases does not allow the identification of Brucella isolates. In this work, we constructed a Brucella MALDI-TOF MS reference database using VITEK MS. We generated 590 spectra from 84 different strains (including rare or atypical isolates) to cover this bacterial genus. We then applied a novel biomathematical approach to discriminate different species. This allowed accurate identification of Brucella isolates at the genus level with no misidentifications, in particular as the closely related and less pathogenic Ochrobactrum genus. The main zoonotic species (B. melitensis, B. abortus and B. suis) could also be identified at the species level with an accuracy of 100%, 92.9% and 100%, respectively. This MALDI-TOF reference database will be the first Brucella database validated for diagnostic and accessible to all VITEK MS users in routine. This will improve the diagnosis and control of brucellosis by allowing a rapid identification of these pathogens.

Brucella are bacteria that mainly infect animals. They can also be transmitted to humans and cause a serious disease called brucellosis. Half the world's population is considered exposed, especially in the poorest rural areas. Experts agree that prompt identification of Brucella isolates is essential to provide appropriate treatment to patients and to control epidemiological outbreaks. Mis-identification of these highly infectious pathogens may lead to delays in diagnosis, but also to increased risks of accidental exposure for laboratory workers. MALDI-TOF mass spectrometry is now the first line of bacterial identification in many routine diagnostic laboratories. However, not all clinical mass spectrometers can identify Brucella. In this work, we updated a database with Brucella spectra to improve the performance of MALDI-TOF mass spectrometers. These instruments will now be able to identify accurately Brucella isolates. This will greatly improve the diagnosis of brucellosis.

First isolation of Brucella pinnipedialis and detection of Brucella antibodies from bearded seals Erignathus barbatus

Brucella species infecting marine mammals was first reported in 1994 and in the years since has been documented in various species of pinnipeds and cetaceans. While these reports have included species that inhabit Arctic waters, the few available studies on bearded seals Erignathus barbatus have failed to detect Brucella infection to date. We report the first isolation of Brucella pinnipedialis from a bearded seal. The isolate was recovered from the mesenteric lymph node of a bearded seal that stranded in Scotland and typed as ST24, a sequence type associated typically with pinnipeds. Furthermore, serological studies of free-ranging bearded seals in their native waters detected antibodies to Brucella in seals from the Chukchi Sea (1990-2011; 19%) and Svalbard (1995-2007; 8%), whereas no antibodies were detected in bearded seals from the Bering Sea or Bering Strait or from captive bearded seals.