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Biomedical subjects

D Raoult

Publications and source records attributed to D Raoult.

At least 91 records · Page 5Linked to original sources
PubMed2000

Isolation in endothelial cell cultures of chlamydia trachomatis LGV (Serovar L2) from a lymph node of a patient with suspected cat scratch disease.

An inguinal lymph node, removed from a 21-year-old Romanian man suspected of having cat scratch disease, was sent to our laboratory for Bartonella culture. Lymph node specimens were inoculated on blood-enriched agar and in an endothelial cell culture system using the centrifugation shell vial technique. Bacteria were grown in cell monolayers and detected as positive with an anti-Bartonella henselae rabbit serum. However, such bacteria were identified as Chlamydia trachomatis biovar LGV serovar L2 by PCR sequencing techniques. Pathological examination of tissue biopsies was compatible with either lymphogranuloma venereum or cat scratch disease. The shell vial system is suitable for isolation of intracellular pathogens responsible for chronic lymphadenopathies, including C. trachomatis, Bartonella species, Francisella tularensis, and mycobacteria. However, care should be taken when identifying Chlamydia spp. and Bartonella spp. using polyclonal antibodies, since species of both genera have common antigens which are responsible for cross-reactions.

Adult↗
PubMed2000

rpoB gene analysis as a novel strategy for identification of spirochetes from the genera Borrelia, Treponema, and Leptospira.

Spirochetes are emerging pathogens for which culture and identification are partly unresolved. In fact, 16S rRNA-based sequencing is by far the most widely used PCR methodology that is able to detect such uncultivable pathogens. However, this assay actually has some limitations linked to potential problems of contamination, which hampers diagnosis. To circumvent this, we have devised a simple PCR strategy involving targeting of the gene encoding the RNA polymerase beta subunit (rpoB), a highly conserved enzyme. The complete sequence of the Leptospira biflexa (serovar patoc) rpoB gene was determined and compared with the published sequences for Borrelia burgdorferi and Treponema pallidum. From the resulting analysis, degenerate nucleotide primers were designed and tested for their ability to amplify a portion of the rpoB gene from various spirochetes. Using two different pairs of these primers, we succeeded in obtaining specific rpoB-amplified fragments for all members of the genera Leptospira, Treponema, and Borrelia tested and no other bacteria. Our findings may have significant implications for the development of a new tool for the identification of spirochetes, especially if clinical samples are contaminated or when the infecting strain is uncultivable.

Borrelia↗
PubMed2000

Genetic classification of "Rickettsia heilongjiangii" and "Rickettsia hulinii," two Chinese spotted fever group rickettsiae.

To determine the phylogenetic position of two new rickettsial strains isolated from ticks in China, 16S ribosomal DNA, gltA, and ompA (apart from the tandem repeat units) genes were amplified by PCR and sequenced. The phylogenetic relationships between these strains and other rickettsiae were inferred from the comparison of sequences of the three genes by the parsimony, neighbor-joining, and maximum-likelihood methods. The results demonstrated that the 054 strain, a rickettsia pathogenic in humans, and the HL-93 strain were related and clustered together with Rickettsia japonica. Significant statistical bootstrap values (100 and 92%) supported the nodes in this cluster. Based on previous genotypic and antigenic data and the phylogenetic analysis presented here, the 054 and HL-93 strains should be considered as new species, and we formally propose that they be named "Rickettsia heilongjiangii" and "Rickettsia hulinii," respectively.

Animals↗
PubMed2000

Quantitative analysis of valvular lesions during Bartonella endocarditis.

Cardiac valve pathology was evaluated in 15 patients with confirmed diagnosis of Bartonella endocarditis. Ten were infected by Bartonella quintana and 5 by Bartonella henselae. Histologic features of these cases, including fibrosis, calcification, vegetation, pattern of inflammation, and vascularization, were compared with those of valves from 25 cases of non-Bartonella endocarditis as controls using a computerized quantitative image analysis. Pathologic and immunohistologic testing for localization of Bartonella species in resected valves included Warthin-Starry stain and polyclonal antibody-based immunodetection. Compared with other cases of infective endocarditis, cases of Bartonella endocarditis are more fibrotic and calcified, less vascularized, with less extensive vegetation and chronic inflammation. These pathologic changes are suggestive of a prolonged infection. Warthin-Starry stain and immunohistologic testing demonstrated the presence of the organism, respectively, in 11 and 10 of the 13 tested valves. Results of both staining methods showed microorganisms in extracellular locations and in regions unaccompanied by inflammation. Pathology and immunohistology may contribute to the etiologic diagnosis of Bartonella endocarditis when serology and molecular techniques are not available.

Adult↗
PubMed2000

Short report: isolation and identification of two spotted fever group rickettsial strains from patients in Catalonia, Spain.

Two rickettsial strains, 16B (previously isolated) and FB1, were isolated from blood from patients with Mediterranean spotted fever in Catalonia, Spain. These are the only 2 human rickettsial isolates of the spotted fever group obtained so far in Spain. These strains were identified by the polymerase chain reaction and sequence analysis of a fragment of the outer membrane protein A (ompA) gene. The partial ompA sequence was found to be 100% identical with that of Rickettsia conorii (Malish 7 strain) for both strains. These results confirm the presence of R. conorii in Catalonia, despite the fact that in a previous study, no R. conorii were isolated, but a new rickettsial strain of the spotted fever group (Bar29) was isolated from dog ticks (Rhipicephalus sanguineus) in Catalonia. Further studies are necessary to get a better knowledge of the epidemiology of rickettsiae in Catalonia.

Bacterial Outer Membrane Proteins↗
PubMed2000

[Determination of Ehrlichia genome size by pulse gel electrophoresis].

Ehrlichia infections are more and more common in the USA and Europe. The genetics and genome organization of Ehrlichia are little studied due to great difficulties in cultivating these bacteria. Pulse gel electrophoresis was first used to determine the sizes of a genome of 3 representatives of the genus Ehrlichia. The sizes of a genome was established for E. sennetsu (881 kb), for E. risticii (867 kb), E. chaffeensis (1,236 kb).

DNA Fragmentation↗
PubMed1999

Subversion of monocyte functions by coxiella burnetii: impairment of the cross-talk between alphavbeta3 integrin and CR3.

Several intracellular pathogens exploit macrophages as a niche for survival and replication. The success of this strategy requires the subversion or the avoidance of microbicidal functions of macrophages. Coxiella burnetii, the agent of Q fever, is a strictly intracellular bacterium that multiplies in myeloid cells. The survival of C. burnetii may depend on the selective use of macrophage receptors. Virulent C. burnetii organisms were poorly internalized but survived successfully in human monocytes, whereas avirulent variants were efficiently phagocytosed but were also rapidly eliminated. The uptake of avirulent organisms was mediated by leukocyte response integrin (alphavbeta3 integrin) and CR3 (alphaMbeta2 integrin), as demonstrated by using specific Abs and RGD sequence-containing peptides. The phagocytic efficiency of CR3 depends on its activation via alphavbeta3 integrin and integrin-associated protein. Indeed, CR3-mediated phagocytosis of avirulent C. burnetii was abrogated in macrophages from integrin-associated protein-/- mice. In contrast, the internalization of virulent C. burnetii organisms involved the engagement of alphavbeta3 integrin but not that of CR3. The pretreatment of monocytes with virulent C. burnetii organisms prevented the CR3-mediated phagocytosis of zymosan particles and CR3 activation assessed by the expression of the 24 neo-epitope. We conclude that the virulence of C. burnetii is associated with the engagement of alphavbeta3 integrin and the impairment of CR3 activity, which probably results from uncoupling alphavbeta3 integrin from integrin-associated protein. This study describes a strategy not previously reported of phagocytosis modulation by intracellular pathogens.

Antigens, CD↗
PubMed1999

Intraspecies diversity of Coxiella burnetii as revealed by com1 and mucZ sequence comparison.

Coxiella burnetii is classified within the gamma subgroup of the Proteobacteria. All strains tested to date have an identical 16S rRNA sequence but 20 different genotypes have been determined by pulsed field gel electrophoresis (PFGE). In this study, intraspecies genetic diversity was investigated by sequence comparison of 715 bp of the Com1 encoding gene (com1) and 774 bp of the MucZ encoding gene (mucZ) in 37 strains isolated from animals and humans with acute or chronic Q fever in Europe, North America and Africa. Five and four groups were established from sequence analysis of com1 and mucZ, respectively. Neither relation of the defined groups to geographical distribution of the isolates was noted nor relation to disease form (acute/chronic). The same isolates were grouped together regardless of the gene being investigated. Comparison of the five proposed groups to previous groups, yielded after digestion by NotI PFGE, allowed for an intermediate classification of C. burnetii isolates between those obtained by using 16S rDNA (one group) and PFGE (20 groups).

Animals↗
PubMed1999

[African Rickettsia infections].

EPIDEMIOLOGY: African rickettsiasis is transmitted by Rickettsia africae, a cattle tick. Amblyomma spp. is an emerging rickettsiasis in sub-sehalian Afric described in 1992. Seroepidemiology studies conducted in Africa show that it is probably the most widespread rickettsiasis in the sorld. In addition, the development of tourist activities in southern African countries has led to an increase in the number of reported cases in subjects returning from endemic areas. A high serprevalence of anti R. africae anticodies has been recently reported in the guadeloupe (French East Indies) population as well as one documented infection. CLINIC: The clinical expression of African tick rickettsiasis includes fevder, headache, inoculation scar, locoredgional node enlargement, and an inconsistent sometimes vesicular rash. The diagnosis is made on the basis of serological findings and cross absorption of anti R. africae and R. conorii antibodies and/or isolation or gene amplification of R. africae from inoculation scar biopsies.

Africa↗
PubMed1999

Hyperendemic focus of Q fever related to sheep and wind.

Q fever is a worldwide zoonosis which is caused by Coxiella burnetii and presents as both acute or chronic cases. The disease can be transmitted from animal reservoirs to humans by the inhalation of infected aerosols. The authors investigated the epidemiology of Q fever in the Bouches-du-Rhône district of southern France. The study area was centered around the small town of Martigues near the cities of Marseille and Aix-en-Provence, where the incidence of the disease seemed higher than in neighboring areas. Epidemiologic data included sheep breeding and wind. Between 1990 and 1995, Q fever was diagnosed in 289 patients, leading to an incidence rate of 35.4 per 100,000 in the study area (range: 6-132), compared with 6.6 in the area of Marseille, and 11.4 in the area of Aix-en-Provence. There was a graphical and statistical relation between the sheep densities, the incidence of the disease, and the strong, local wind known as the Mistral, which blows from the northwest. Although Coxiella burnetii transmission is multifactorial, we may speculate that the high endemicity in the study area is related to a contamination by aerosols because the Mistral blows through the local steppe where 70,000 sheep are bred. This public health problem requires further studies in order to confirm this hypothesis, and to identify more individual and preventable risk factors.

Adolescent↗
PubMed1999

Determination of the genome size of Ehrlichia spp., using pulsed field gel electrophoresis.

Ehrlichiae are obligatory intracellular, Gram-negative bacteria which belong to the alpha subclass of the phylum Proteobacteria and are responsible for infectious diseases of humans. Little is known about genetics and genomic organization of Ehrlichia spp. The genome sizes of four representatives of the genus Ehrlichia were determined for the first time by pulsed field gel electrophoresis. The sizes for E. sennetsu, E. risticii, E. chaffeensis (strain Arkansas and strain 91HE17), and the HGE agent were 878.5 kb, 880.3 kb, 1225.8 kb, 1262.3 kb and 1494 kb respectively.

Animals↗
PubMed1999

[Bartonella infection in humans].

BARTONELLA BACILLIFORMIS: Among the 3 species of Bartonella known to be human pathogens, B. bacilliformis causes Carriun's disease, which manifests an acute phase (Oroya fever) and a chronic phase marked by benign skin eruption with wart like macules of vascular origin. Until 1993, B. bacilliformis was considered to be the only species in Bartonella genus. In 1993, species formally in the Rochalimaea genus were designated as Bartonella species. BARTONELLA QUINTANA: This species causes trench fever. It is also the causal agent in cases of bacillary angiomatosis, septicemia, endocarditis with negative blood cultures, and chronic nodal infections, particularly in immunosuppressed patients. Trench fever is transmitted by body lice and is becoming more prevalent, particularly in the homeless. BARTONELLA HENSELAE: This agent causes bacillary angiomatosis, visceral peliosis, septicemia, endocarditis and cat-scratch disease. Transmitted by cats, and perhaps by lice, cat-scratch disease is one of the most frequent zoonoses. OTHER SPECIES: The spectrum of Bartonella infections has continued to widen these last 5 years. The role of B. elizabethae and C. clarridgeiae as human pathogens remains to be defined [abstract corrected]

Bartonella Infections↗