Muriel Vayssier-Taussat

Genomic analysis of Bartonella identifies type IV secretion systems as host adaptability factors

The bacterial genus Bartonella comprises 21 pathogens causing characteristic intraerythrocytic infections. Bartonella bacilliformis is a severe pathogen representing an ancestral lineage, whereas the other species are benign pathogens that evolved by radial speciation. Here, we have used comparative and functional genomics to infer pathogenicity genes specific to the radiating lineage, and we suggest that these genes may have facilitated adaptation to the host environment. We determined the complete genome sequence of Bartonella tribocorum by shotgun sequencing and functionally identified 97 pathogenicity genes by signature-tagged mutagenesis. Eighty-one pathogenicity genes belong to the core genome (1,097 genes) of the radiating lineage inferred from genome comparison of B. tribocorum, Bartonella henselae and Bartonella quintana. Sixty-six pathogenicity genes are present in B. bacilliformis, and one has been lost by deletion. The 14 pathogenicity genes specific for the radiating lineage encode two laterally acquired type IV secretion systems, suggesting that these systems have a role in host adaptability.

Role of Hippoboscidae Flies as Potential Vectors of Bartonella spp. Infecting Wild and Domestic Ruminants

ABSTRACT The putative role of biting flies in Bartonella transmission among ruminants was investigated. Amplification of the Bartonella citrate synthase gene from 83 Hippoboscidae was detected in 94% of 48 adult Lipoptena cervi flies, 71% of 17 adult Hippobosca equina flies, 100% of 20 adult Melophagus ovinus flies, and 100% of 10 M. ovinus pupae. Our findings suggest that Hippoboscidae play a role in the transmission of Bartonella among ruminants. The vertical transmission of Bartonella in M. ovinus and the presence of Bartonella DNA in all samples suggest a symbiotic association between Bartonella and M. ovinus.

The Trw Type IV Secretion System of Bartonella Mediates Host-Specific Adhesion to Erythrocytes

Bacterial pathogens typically infect only a limited range of hosts; however, the genetic mechanisms governing host-specificity are poorly understood. The α-proteobacterial genus Bartonella comprises 21 species that cause host-specific intraerythrocytic bacteremia as hallmark of infection in their respective mammalian reservoirs, including the human-specific pathogens Bartonella quintana and Bartonella bacilliformis that cause trench fever and Oroya fever, respectively. Here, we have identified bacterial factors that mediate host-specific erythrocyte colonization in the mammalian reservoirs. Using mouse-specific Bartonella birtlesii, human-specific Bartonella quintana, cat-specific Bartonella henselae and rat-specific Bartonella tribocorum, we established in vitro adhesion and invasion assays with isolated erythrocytes that fully reproduce the host-specificity of erythrocyte infection as observed in vivo. By signature-tagged mutagenesis of B. birtlesii and mutant selection in a mouse infection model we identified mutants impaired in establishing intraerythrocytic bacteremia. Among 45 abacteremic mutants, five failed to adhere to and invade mouse erythrocytes in vitro. The corresponding genes encode components of the type IV secretion system (T4SS) Trw, demonstrating that this virulence factor laterally acquired by the Bartonella lineage is directly involved in adherence to erythrocytes. Strikingly, ectopic expression of Trw of rat-specific B. tribocorum in cat-specific B. henselae or human-specific B. quintana expanded their host range for erythrocyte infection to rat, demonstrating that Trw mediates host-specific erythrocyte infection. A molecular evolutionary analysis of the trw locus further indicated that the variable, surface-located TrwL and TrwJ might represent the T4SS components that determine host-specificity of erythrocyte parasitism. In conclusion, we show that the laterally acquired Trw T4SS diversified in the Bartonella lineage to facilitate host-restricted adhesion to erythrocytes in a wide range of mammals.

Bartonella spp. DNA associated with biting flies from California.

Bartonella DNA was investigated in 104 horn flies (Haematobia spp.), 60 stable flies (Stomoxys spp.), 11 deer flies (Chrysops spp.), and 11 horse flies (Tabanus spp.) collected on cattle in California. Partial sequencing indicated B. bovis DNA in the horn fly pool and B. henselae type M DNA in one stable fly.

Effects of Cow Age and Pregnancy on Bartonella Infection in a Herd of Dairy Cattle

ABSTRACT Bartonella spp. are small hemotropic bacteria infecting mammals. Four Bartonella species have been recently described in cattle and wild ruminants. To date, the biology and possible pathogenic role of Bartonella species isolated from ruminants are poorly understood. Therefore, a dairy herd of 448 cows and heifers was surveyed in order to establish the prevalence of Bartonella bovis and B. chomelii infections, the level of bacteremia, and the relationship between bacteremia and age or pregnancy status. The putative impact of Bartonella infection on production performance (individual milk cell count, milk yield) and reproductive status (success of artificial insemination [AI], placental retention, embryonic death, and abortion) was also assessed. The overall mean prevalence of B. bovis bacteremia was 59%, with the highest prevalence in heifers (92.5%). No B. chomelii was isolated, and 95% (114/120) of the B. bovis strains isolated and tested by PCR-restriction fragment length polymorphism belonged to type I. The level of bacteremia was higher in pregnant cows than in nonpregnant cows (P = 0.05), and the level of bacteremia rose during the last two-thirds of gestation (P < 0.001). There was no correlation between bacteremia and milk yield, individual milk cell count, success of first AI, interval between two calvings, or incidence of abortion and embryonic death. The interval from calving to first AI was shorter and the incidence of placental retention was lower in bacteremic animals than in nonbacteremic ones (P = 0.03 and P = 0.01, respectively).

Prevalence of Anaplasma phagocytophilum, Rickettsia sp. and Borrelia burgdorferi sensu lato DNA in Questing Ixodes ricinus Ticks from France

Abstract:u2002 A total of 4701 Ixodes ricinus, collected during the summer of 2003, were analyzed for three pathogens. DNA was detected from the three pathogens. Co‐detection of more than one pathogen was observed.

Identification of mechanisms involved in iron and haem uptake in Bartonella birtlesii: in silico and in vivo approaches.

Beijing Genome Institute, Beijing,ChinaINTRODUCTIONBartonella birtlesii (B. birtlesii), like other Bartonellaspecies, has to face various conditions with regardto the presence of haem in its environments(arthropods, mammals, intra- or extracellular).B. birtlesiihas an intraerythrocytic lifestyle in itsnatural host, the mouse. Inside mice, the extra-cellular free haem concentration is low. In con-trast, when invading and multiplying inside theerythrocyte, B. birtlesii has to challenge toxic highhaem concentrations. Similar to other Bartonellaspecies [1], the B. birtlesii genome does not encodefor the haem biosynthesis pathway. The presenceof a haem uptake system is thus important forBartonellae. Here we investigated the function oftwo components of a putative haem uptakesystem encoded in B. birtlesii, and other Bartonellaegenomes.RESULTS AND DISCUSSIONIn silico identification of B. birtlesii genespotentially involved in iron and⁄or haem uptakeAnalysis of the B. birtlesii genome reveals that,similar to other Bartonella species, this a-proteo-bacterium contains only inner membrane ironABC transporters. Genes encoding for an outermembrane iron transporter or a complete sidero-phore biosynthesis pathway are missing in theB. birtlesii genome. Also, the B. birtlesii genomedoes not encode for iron storage proteins (Ftn,Bfn, Dps). In contrast, Bartonellae genomesencode for a complete putative haem transportsystem (Fig. 1). Similar to other bacteria likeNeisseria meningitidis, Bartonellae could use haemas an iron source after its transport and itsdegradation into the cytoplasm. Regulation of theiron-related processes in could simi-larly to other a-proteobacteria involve Mur⁄Fur,RirA and Irr regulators encoded in its genome.Irr was shown to be involved in the regulation ofan outer membrane haem transporter in Brady-rhizobium japonicum. The modulation of the leveland the activity of the components of the haemuptake machinery might be important for theBartonellae lifestyle. Characterisation of Bartonellatribocorum hutA, tonB and exbB mutants as abac-teriaemic strains also underlines the importanceof the haem uptake process in Bartonellae [2].We undertook a functional characterisation ofB. birtlesii HutA [3] and TonB [4], two compo-nents required for the transport of haem throughthe outer membrane. HutA, already characterisedin Vibrio cholerae, transports haem through theouter membrane and requires energy transmittedby the TonB protein [3].Expression and activity of TonB from B. birtlesiiexpressed in Escherichia coliThe tonB structural gene from B. birtlesii wasamplified and cloned in vector pBAD24 givingpBAD24::tonBB.bir. To test activity of TonB fromB. birtlesii, we introduced plasmid pBAD24::ton-BB.bir in strain C600tonB. The strain C600tonBpBAD24::tonBB.bir was tested for growth on LBplates in the presence of the strong Fe

Tick-borne pathogen detection: what's new?

Ticks and the pathogens they transmit constitute a growing burden for human and animal health worldwide. Traditionally, tick-borne pathogen detection has been carried out using PCR-based methods that rely in known sequences for specific primers design. This approach matches with the view of a single-pathogen epidemiology. Recent results, however, have stressed the importance of coinfections in pathogen ecology and evolution with impact in pathogen transmission and disease severity. New approaches, including high-throughput technologies, were then used to detect multiple pathogens, but they all need a priori information on the pathogens to search. Thus, those approaches are biased, limited and conceal the complexity of pathogen ecology. Currently, next generation sequencing (NGS) is applied to tick-borne pathogen detection as well as to study the interactions between pathogenic and non-pathogenic microorganisms associated to ticks, the pathobiome. The use of NGS technologies have surfaced two major points: (i) ticks are associated to complex microbial communities and (ii) the relation between pathogens and microbiota is bidirectional. Notably, a new challenge emerges from NGS experiments, data analysis. Discovering associations among a high number of microorganisms is not trivial and therefore most current NGS studies report lists of microorganisms without further insights. Anxa0alternative to this is the combination of NGS with analytical tools such as network analysis to unravel the structure of microbial communities associated to ticks in different ecosystems.

Ticks and tick-borne pathogens of the Caribbean: Current understanding and future directions for more comprehensive surveillance

Ticks are obligate hematophagous arthropods of significant importance to human and veterinary medicine. They transmit a vast array of pathogens, including bacteria, viruses, protozoa, and helminths. Most epidemiological data on ticks and tick-borne pathogens (TBPs) in the West Indies are limited to common livestock pathogens such as Ehrlichia ruminantium, Babesia spp. (i.e., B. bovis and B. bigemina), and Anaplasma marginale, and less information is available on companion animal pathogens. Of note, human tick-borne diseases (TBDs) remain almost completely uncharacterized in the West Indies. Information on TBP presence in wildlife is also missing. Herein, we provide a comprehensive review of the ticks and TBPs affecting human and animal health in the Caribbean, and introduce the challenges associated with understanding TBD epidemiology and implementing successful TBD management in this region. In particular, we stress the need for innovative and versatile surveillance tools using high-throughput pathogen detection (e.g., high-throughput real-time microfluidic PCR). The use of such tools in large epidemiological surveys will likely improve TBD prevention and control programs in the Caribbean.

High Throughput Sequencing and Network Analysis Disentangle the Microbial Communities of Ticks and Hosts Within and Between Ecosystems

We aimed to develop a framework, based on graph theory, to capture the ecological meaning behind pure pair comparisons of microbiome-derived data. As a proof of concept, we applied the framework to analyze the co-occurrence of bacteria in either Ixodes ricinus ticks or the spleen of one of their main hosts, the vole Myodes glareolus. As a secondary lymphoid organ, the spleen acts as a filter of blood and represents well the exposure to microorganisms circulating in the blood; including those acquired and transmitted by ticks during feeding. The microbiome of 301 and 269 individual tick and vole samples, respectively, were analyzed using next generation sequencing (NGS) of 16S rRNA. To assess the effect of habitat on ecological communities of bacteria associated to ticks and voles, two different biotopes were included in the study, forest, and ecotone. An innovative approach of NGS data analysis combining network analysis and phylogenies of co-occuring of bacteria was used to study associations between bacteria in individual samples. Of the 126 bacterial genera found in ticks and voles, 62% were shared by both species. Communities of co-occurring bacteria were always more phylogenetically diverse in ticks than in voles. Interestingly, ~80% of bacterial phylogenetic diversity was found in ~20% of ticks. This pattern was not observed in vole-associated bacteria. Results revealed that the microbiome of I. ricinus is only slightly related to that of M. glareolus and that the biotope plays the most important role in shaping the bacterial communities of either ticks or voles. The analysis of the phylogenetic signal of the network indexes across the 16S rRNA-derived tree of bacteria suggests that the microbiome of both ticks and voles has high phylogenetic diversity and that closest bacterial genera do not co-occur. This study shows that network analysis is a promising tool to unravel complex microbial communities associated to arthropod vectors and vertebrate hosts.