Morphological analysis of the sheathed flagellum of Brucella melitensis

<p>Abstract</p> <p>Background</p> <p>It was recently shown that <it>B. melitensis </it>is flagellated. However, the flagellar structure remains poorly described.</p> <p>Findings</p> <p>We analyzed the structure of the polar sheathed flagellum of <it>B. melitensis </it>by TEM analysis and demonstrated that the Ryu staining is a good method to quickly visualize the flagellum by optical microscopy. The TEM analysis demonstrated that an extension of the outer membrane surrounds a filament ending by a club-like structure. The Δ<it>ftcR</it>, Δ<it>fliF</it>, Δ<it>flgE </it>and Δ<it>fliC </it>flagellar mutants still produce an empty sheath.</p> <p>Conclusions</p> <p>Our results demonstrate that the flagellum of <it>B. melitensis </it>has the characteristics of the sheathed flagella. Our results also suggest that the flagellar sheath production is not directly linked to the flagellar structure assembly and is not regulated by the FtcR master regulator.</p

Global Analysis of Quorum Sensing Targets in the Intracellular Pathogen Brucella melitensis 16 M

Many pathogenic bacteria use a regulatory process termed quorum sensing (QS) to produce and detect small diffusible molecules to synchronize gene expression within a population. In Gram-negative bacteria, the detection of, and response to, these molecules depends on transcriptional regulators belonging to the LuxR family. Such a system has been discovered in the intracellular pathogen Brucella melitensis, a Gram-negative bacterium responsible for brucellosis, a worldwide zoonosis that remains a serious public health concern in countries were the disease is endemic. Genes encoding two LuxR-type regulators, VjbR and BabR, have been identified in the genome of B. melitensis 16 M. A DeltavjbR mutant is highly attenuated in all experimental models of infection tested, suggesting a crucial role for QS in the virulence of Brucella. At present, no function has been attributed to BabR. The experiments described in this report indicate that 5% of the genes in the B. melitensis 16 M genome are regulated by VjbR and/or BabR, suggesting that QS is a global regulatory system in this bacterium. The overlap between BabR and VjbR targets suggest a cross-talk between these two regulators. Our results also demonstrate that VjbR and BabR regulate many genes and/or proteins involved in stress response, metabolism, and virulence, including those potentially involved in the adaptation of Brucella to the oxidative, pH, and nutritional stresses encountered within the host. These findings highlight the involvement of QS as a major regulatory system in Brucella and lead us to suggest that this regulatory system could participate in the spatial and sequential adaptation of Brucella strains to the host environment.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

The genus Brucella and clinical manifestations of brucellosis

Infection with bacteria of the genus Brucella results in major economic and political impact by causing reproductive diseases in a significant number of domestic animal species. Moreover, it has a great social significance, since many species are capable of causing human infection, with severe consequences. Dissemination of knowledge on a specific disease is an essential step for its control. Considering that brucellosis is still the most prevalent zoonosis in the world, information about taxonomy, clinical signs in domestic animals and humans are crucial for attempting to reduce the prevalence of this disease. The recent isolation and characterization of non-classical species of Brucella indicates that a lot remains to be discovered about this genus. Nevertheless, due to the social-economic importance of brucellosis, this review aims to clarify points related to taxonomy of the genus and describe the clinical relevance of infection in humans and domestic animals

Exploring the Diversity of Field Strains of Brucella abortus Biovar 3 Isolated in West Africa

Brucellosis is one of the most widespread bacterial zoonotic diseases in the world, affecting both humans and domestic and wild animals. Identification and biotyping of field strains of Brucella are of key importance for a better knowledge of the epidemiology of brucellosis, for identifying appropriate antigens, for managing disease outbreaks and for setting up efficient preventive and control programmes. Such data are required both at national and regional level to assess potential threats for public health. Highly discriminative genotyping methods such as the multiple locus variable number of tandem repeats analysis (MLVA) allow the comparison and assessment of genetic relatedness between field strains of Brucella within the same geographical area. In this study, MLVA biotyping data retrieved from the literature using a systematic review were compared using a clustering analysis and the Hunter-Gaston diversity index (HGDI). Thus, the analysis of the 42 MLVA genotyping results found in the literature on West Africa [i.e., from Ivory Coast (1), Niger (1), Nigeria (34), The Gambia (3), and Togo (3)] did not allow a complete assessment of the actual diversity among field strains of Brucella. However, it provided some preliminary indications on the co-existence of 25 distinct genotypes of Brucella abortus biovar 3 in this region with 19 genotypes from Nigeria, three from Togo and one from Ivory Coast, The Gambia, and Niger. The strong and urgent need for more sustainable molecular data on prevailing strains of Brucella in this sub-region of Africa and also on all susceptible species including humans is therefore highlighted. This remains a necessary stage to allow a comprehensive understanding of the relatedness between field strains of Brucella and the epidemiology of brucellosis within West Africa countries

Genotyping and strain distribution of Mycobacterium avium subspecies hominissuis isolated from humans and pigs in Belgium, 2011-2013

&lt;p&gt;Mycobacterium avium represents a health concern for both humans and pigs. The characterisation of its subspecies is an important step improving the understanding of the epidemiology and the control of this pathogen. Ninety-two human M. avium strains were selected for a retrospective study. Subspecies determination by rpoB sequencing and IS1245/IS901 analysis showed that 98.9% of Belgian human M. avium strains belong to the subspecies hominissuis (MAH). Some of these MAH strains present particular IS1245/IS901 profiles (absence of IS1245 and false IS901 detection provoked by the presence of ISMav6). In addition, 54 MAH strains isolated from submandibular lymph nodes of Belgian pigs with lymphadenitis were included in this study. Genotyping of human and porcine isolates was performed using multispacer sequence typing (MST). In total, 49 different MST types were identified among pig (n = 11) and human (n = 43) MA isolates, with only five shared by both hosts. Among these MST types, 34 were newly identified. Our findings demonstrate the extensive genetic diversity among MAH isolates. Some genotypes were more prevalent in human or pigs but no correlation was observed between MST type and place of residence or the farm of origin for human and porcine isolates respectively, suggesting an environmental source of infection.&lt;/p&gt;</p

Coxiella burnetii, agent de la fièvre Q

&lt;p&gt;Q fever is a zoonosis of worldwide distribution with the exception of New Zealand. It is caused by an&lt;br /&gt; intracellular bacterium, Coxiella burnetii. The disease often goes underdiagnosed because the main manifestation&lt;br /&gt; of its acute form is a general self-limiting flu-like syndrome. The Dutch epidemics renewed attention to this&lt;br /&gt; disease, which was less considered before. This review summarizes the description of C. burnetii (taxonomy,&lt;br /&gt; intracellular cycle, and genome) and Q fever disease (description, diagnosis, epidemiology, and pathogenesis).&lt;br /&gt; Finally, vaccination in humans and animals is also considered&lt;/p&gt;</p