Brucella species are responsible for brucellosis, a worldwide zoonotic disease causing abortion in domestic animals and Malta fever in humans. Based on host preference, the genus is divided into six species. Brucella abortus, B. melitensis, and B. suis are pathogenic to humans, whereas B. ovis and B. neotomae are nonpathogenic to humans and B. canis human infections are rare. Limited genome diversity exists among Brucella species. Comparison of Brucella species whole genomes is, therefore, likely to identify factors responsible for differences in host preference and virulence restriction. To facilitate such studies, we used the complete genome sequence of B. melitensis 16M, the species highly pathogenic to humans, to construct a genomic microarray. Hybridization of labeled genomic DNA from Brucella species to this microarray revealed a total of 217 open reading frames (ORFs) altered in five Brucella species analyzed. These ORFs are often found in clusters (islands) in the 16M genome. Examination of the genomic context of these islands suggests that many are horizontally acquired. Deletions of genetic content identified in Brucella species are conserved in multiple strains of the same species, and genomic islands missing in a given species are often restricted to that particular species. These findings suggest that, whereas the loss or gain of genetic material may be related to the host range and virulence restriction of certain Brucella species for humans, independent mechanisms involving gene inactivation or altered expression of virulence determinants may also contribute to these differences.Brucellosis is a zoonotic disease endemic in many areas of the world and is characterized by chronic infections, abortion, and sterility (7). In humans, brucellosis is a systemic, febrile illness resulting in osteoarthritis, endocarditis, and several neurological disorders (7,53). Brucellosis is caused by many species belonging to the genus Brucella that are aerobic facultative intracellular bacteria. Brucella species are closely related to intracellular symbionts and pathogens of plants and animals and are classified as ␣ 2 -proteobacteria based on rRNA sequence comparison (36).The genus Brucella consists of six species, designated on the basis of host preference, antigenic and biochemical characteristics as Brucella melitensis (goats and sheep), B. abortus (cattle), B. suis (pigs), B. canis (dogs), B. ovis (sheep), and B. neotomae (wood rats) (6). B. abortus, B. melitensis, and B. suis can all infect humans with similar serious disease consequences (7). B. melitensis, originally isolated as a pathogen of goats and sheep, is highly pathogenic and a frequent cause of human brucellosis. In contrast, human infections of B. ovis and B. neotomae have not been reported, and B. canis rarely causes infection in humans. Human brucellosis occurs via contact with infected animals or animal products and is common in countries where the disease is endemic in domestic animals (13). Brucella also can be readily dispersed through aerosol...

Despite progress in mouse models of brucellosis, much remains unknown regarding Brucella dissemination and tissue localization. Here, we report the dynamics of Brucella infection in individual mice using bioluminescent Brucella melitensis. Bioluminescent imaging of infected interferon regulatory factor-1 knockout (IRF-1(-/-)) mice identified acute infection in many tissues. Brucella was found to replicate in the salivary glands of IRF-1(-/-) and wild-type C57BL/6 mice suggesting a previously unknown tissue preference. Establishing a niche in this region may have relevance in humans where infection can result from ingestion of few bacteria. Sublethal infection of IRF-1(-/-) mice resulted in chronic Brucella localization in tail joints, an infection parallel to osteoarticular brucellosis in humans. Importantly, bioluminescent imaging rapidly identified attenuated EZ::TN/lux mutants in infected mice and revealed differences in dissemination, thereby defining the contribution of Brucella genes to virulence and tissue localization. Surprisingly, a virB mutant, though defective in persistence, disseminated similarly to virulent Brucella, suggesting bacterial spread is independent of VirB proteins that are important for intracellular survival. Together, our results reveal kinetics of acute and chronic Brucella infection in individual mice that parallels human infection as well as readily identified attenuated bacteria. Our approach facilitates identifying virulence determinants that may control tissue specific replication and may help develop therapeutics to overcome Brucella-induced chronic debilitating conditions.

In vivo bioluminescence imaging is a persuasive approach to investigate a number of issues in microbial pathogenesis. Previously, we have applied bioluminescence imaging to gain greater insight into Brucella melitensis pathogenesis. Endowing Brucella with bioluminescence allowed direct visualization of bacterial dissemination, pattern of tissue localization, and the contribution of Brucella genes to virulence. In this report, we describe the pathogenicity of three attenuated bioluminescent B. melitensis mutants, GR019 (virB4), GR024 (galE), and GR026 (BMEI1090-BMEI1091), and the dynamics of bioluminescent virulent bacterial infection following vaccination with these mutants. The virB4, galE, and BMEI1090-BMEI1091 mutants were attenuated in interferon regulatory factor 1-deficient (IRF-1 ؊/؊ ) mice; however, only the GR019 (virB4) mutant was attenuated in cultured macrophages. Therefore, in vivo imaging provides a comprehensive approach to identify virulence genes that are relevant to in vivo pathogenesis. Our results provide greater insights into the role of galE in virulence and also suggest that BMEI1090 and downstream genes constitute a novel set of genes involved in Brucella virulence. Survival of the vaccine strain in the host for a critical period is important for effective Brucella vaccines. The galE mutant induced no changes in liver and spleen but localized chronically in the tail and protected IRF-1 ؊/؊ and wild-type mice from virulent challenge, implying that this mutant may serve as a potential vaccine candidate in future studies and that the direct visualization of Brucella may provide insight into selection of improved vaccine candidates.Brucella species are important zoonotic pathogens affecting a wide variety of mammals. In agriculturally important domestic animals, these bacteria cause abortion and infertility and are of serious economic concern worldwide (6). In humans, Brucella species constitute potential biowarfare agents, and the infection results in undulant fever, which if untreated, can manifest as orchitis, osteoarthritis, spondylitis, endocarditis, and neurological disorders (12, 46). Currently, no vaccine exists to protect against human brucellosis. Treatment of brucellosis requires a prolonged combination of antibiotic therapy and remains problematic because of potential relapse.Identifying Brucella virulence factors has been of great interest in understanding Brucella pathogenesis and immune evasion. Smooth lipopolysaccharide (LPS) was the first identified virulence factor (25). Brucella LPS has minimal endotoxic effect, blocks complement activation, and protects against bactericidal cationic peptides (28). The O-chain of LPS is also important for the entry of Brucella suis into macrophages through lipid rafts, which permits the Brucella-containing vacuole (BCV) to avoid interaction with the classical endocytic pathway (32, 39). After entry into macrophages, the BCV acidifies and then transiently interacts with EEA-and LAMP1-positive vesicles. After an endosome-like stage, the BCV e...

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Epidemiological evidence suggests that a high intake of dietary fibre is associated with numerous health benefits. Our interest is the potential therapeutic application of dietary fibre manipulation in the context of renal disease and its associated high cardiovascular risk. The relationship between blood pressure and the risk of cardiovascular mortality is well established. In addition uncontrolled hypertension is strongly linked with an increased rate of progression of renal disease. There are studies dating back over 20 years which suggest that modification of fibre intake may have beneficial effects on renal function and blood pressure.