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D Raoult

Publications and source records attributed to D Raoult.

At least 397 records · Page 22Linked to original sources
PubMed1994

Identification of rickettsiae from ticks collected in the Central African Republic using the polymerase chain reaction.

Spotted fever rickettsiosis have been identified on the African continent since their historical description in 1909. However, only Rickettsia conorii and R. africae have been described in Africa, and the current techniques for the detection of rickettsiae in ticks are difficult to apply in large field studies. We report here a preliminary study using genomic amplification by the polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) analysis directly on 310 crushed ticks (Rhipicephalus, Amblyomma, and Haemaphysalis species) collected in 1985 in the Central African Republic. Among 310 specimen tested, 21.6% were positive. The rate of infection ranged from 0% to 64.3%, depending on the tick species. Based on PCR-RFLP, five different rickettsiae profiles were found: R. conorii and R. africae, previously known in Africa, R. rhipicephali, which has never been described in Africa, and two isolates identical to R. massiliae and Mtu5, previously obtained from Rh. turanicus in southern France. This work shows that PCR-RFLP is a powerful tool to study tick collections, and that it is applicable to samples from developing countries. Further work is needed to confirm the identification of the rickettsiae found in this work, using traditional identification procedures.

Animals↗
PubMed1994

Identification of spotted fever group rickettsiae isolated from Dermacentor marginatus and Ixodes ricinus ticks collected in Switzerland.

When 155 ticks collected in different regions of Switzerland were tested by the hemolymph test, 10.3% were found to contain spotted fever group rickettsiae. Six rickettsial isolates were made from Dermacentor marginatus ticks and three were made from Ixodes ricinus ticks. The polymerase chain reaction followed by restriction fragment length polymorphism analysis showed that the Dermacentor ticks were infected with Rickettsia length polymorphism analysis showed that the Dermacentor ticks were infected with Rickettsia slovaca and the Ixodes ticks were infected with a spotted fever group rickettsia. Microimmunofluorescence serologic type, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins, and Western blot assay with polyclonal mouse antisera confirmed the results and determined that the Ixodes were infected with R. helvetica, the only previously described Swiss rickettsia. However, an additional new strain that could not be isolated was detected in one I. ricinus by hemolymph test and provisionally characterized by enzymatic restriction of its amplified DNA.

Animals↗
PubMed1994

Astrakhan fever rickettsiae: antigenic and genotypic analysis of isolates obtained from human and Rhipicephalus pumilio ticks.

Two spotted fever group rickettsia strains, A-108 and A-167, were isolated from the hemolymph of Rhipicephalus pumilio ticks collected in the Astrakhan region of Russia, which is area endemic for Astrakhan fever. These tick isolates were compared with a strain isolated from a patient suffering from Astrakhan fever and with reference spotted fever group rickettsiae strains. New tick isolates and the human strain were identical in their serologic, antigenic, and genetic characteristics by several methods: microimmunofluorescence, protein gel electrophoresis with immunoblotting, polymerase chain reaction followed by restriction endonuclease fragment length polymorphism analysis, and pulsed-field gel electrophoresis (PFGE). Astrakhan fever rickettsiae were found to be serologically and antigenically similar to Israeli spotted fever rickettsiae. Both of them probably belong to a single Rickettsia conorii pathotype complex. Only PFGE pattern analysis could clearly discriminate Astrakhan fever rickettsiae from other isolates.

Animals↗
PubMed1994

Further evidence for the efficacy of imidocarb dipropionate in the treatment of Ehrlichia canis infection.

Three dogs experimentally infected with Ehrlichia canis developed thrombocytopaenia and high antibody titres to E. canis in indirect fluorescent antibody tests. One dog also became leukopaenic. At Weeks 6 and 8 post-infection, the dogs were treated with imidocarb dipropionate (5 mg kg-1 subcutaneously) and a further dose was administered at Week 12 (5 mg kg-1 intramuscularly). Twelve weeks after the last treatment (post-treatment), all dogs had normal platelet counts which persisted for a further 10 weeks until the end of the experiment. The leukopaenia resolved 20 weeks post-treatment. Although antibody titres (< 1/5) to E. canis could not be detected prior to infection, titres of 1/2 560 to 1/5 120 developed by Week 6. By Week 8 post-treatment titres began to decline and by the end of the experiment were 5- to 6-fold serum dilutions lower (1/80 to 1/320). Sub-inoculation experiments 18 weeks post-treatment, failed to cause disease or stimulate antibody responses in susceptible dogs. Serology and sub-inoculation studies on 2 dogs experimentally infected with E. canis but not treated with imidocarb dipropionate, showed that these animals remained infected for the duration of the experiment. The results of these experiments confirm that imidocarb dipropionate is effective in the treatment of canine ehrlichiosis.

Animals↗
PubMed1994

Genomic identification of Rickettsia slovaca among spotted fever group rickettsia isolates from Dermacentor marginatus in Armenia.

Restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR) amplified genes was used for genomic identification of Armenian isolates of the Spotted fever group (SFG) rickettsiae with unclear taxonomic position. Analysis was performed by using one genus-specific primer pair derived from R. prowazekii citrate synthase gene and two species-specific primer pairs derived from R. rickettsii genes for 190 K and 120 K antigens following AluI, PstI and RsaI digestion of amplicons. All tested rickettsial SFG Armenian isolates from Dermacentor marginatus were identified as R. slovaca. The geographic distribution and genetic homogeneity of R. slovaca strains are discussed.

Animals↗
PubMed1994

Purification of rickettsial cultures contaminated by mycoplasmas.

An experimental biological model is proposed for purification of rickettsiae-infected cell cultures from mycoplasma contamination using intravenous mouse infection and subsequent passages on Vero cell monolayers. Mycoplasma-free rickettsial cultures were obtained in mouse brain or spleen suspension within 3 hrs or 3 days, respectively, after mouse inoculation. Ten strains of spotted fever group rickettsiae were purified from mycoplasmas by this procedure.

Animals↗
PubMed1994

A new pathogenic spotted fever group rickettsia from Africa.

A spotted fever group (SFG) rickettsia was isolated in Zimbabwe from a patient with tick-bite, fever, headache and regional lymphadenopathy. A further six isolates were obtained from Amblyomma hebraeum ticks collected in Zimbabwe. These human and tick isolates were indistinguishable from each other, and from an Ethiopian SFG rickettsia, by microimmunofluorescence (MIF), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blotting and polymerase chain reaction followed by restriction fragment length polymorphism analysis (PCR-RFLP). They were, however, distinguishable from other SFG ricketsiae by MIF serotyping and in the case of the most closely related serotypes, Rickettsia conorii and the Israeli SFG rickettsia, by SDS-PAGE and Western blot. PCR-RFLP failed to distinguish between the Zimbabwean and Israeli SFG rickettsia, though each of these gave different digestion products from R. conorii. The Zimbabwean human and tick isolates and the Ethiopian SFG rickettsiae therefore represent a previously undescribed rickettsial serotype which apparently is pathogenic in human beings. It is proposed that the new serotype be named the agent of African tick-bite fever in order to distinguish it from R. conorii, which until now has been recognized as the only SFG rickettsia to infect man in Africa.

Animals↗
PubMed1993

Phylogenic homogeneity of Coxiella burnetii strains as determinated by 16S ribosomal RNA sequencing.

DNA coding for the 16S rRNA of six strains of the obligate intracellular bacterium Coxiella burnetii was directly amplified from lysed host cells using the polymerase chain reaction. The amplification product was sequenced using a linear-PCR procedure and compared with other published 16S rRNA sequences. The results of this analysis confirm the position of C. burnetii in the gamma subgroup of the proteobacteria. The data show that all of the C. burnetii strains are highly related (> 99%) on the basis of 16S rRNA sequences although they had different geographic origins and phenotypic characteristics. The data support a phylogenetic homogeneity of the genus Coxiella with only one species which is C. burnetii.

Base Sequence↗
PubMed1993

Infections with Babesia canis and Ehrlichia canis in dogs in Zimbabwe.

Of 105 dogs examined at a veterinary hospital in Harare, Zimbabwe, 52 per cent had antibodies reactive with Ehrlichia canis in indirect fluorescent antibody tests, 26 per cent had Babesia canis parasites in peripheral blood smears and 17 per cent had both infections. None of the dogs with serological evidence of ehrlichiosis had typical E canis morulae detectable in blood smears. The infections were regarded as incidental findings not readily related to the reasons for examination in 46 per cent of the dogs with antibodies to E canis and 17 per cent of the dogs with both infections. The most common laboratory abnormalities were anaemia and thrombocytopenia and the prevalence and severity of these in concurrent infections were intermediate to those found in individual infections. There were no pathognomonic clinical signs or laboratory abnormalities which could be used to distinguish between individual and concurrent infections. However, there was a significantly higher prevalence of non-regenerative anaemia in dogs with antibodies to E canis than in dogs with both infections. The prevalence of thrombocytopenia was significantly higher in dogs with babesiosis than in dogs with antibodies to E canis and the prevalence of hyperglobulinaemia was significantly higher in dogs with both infections than in dogs with antibodies to E canis.

Anemia↗
PubMed1993

Demonstration of Rickettsia conorii-induced endothelial injury in vivo by measuring circulating endothelial cells, thrombomodulin, and von Willebrand factor in patients with Mediterranean spotted fever.

The endothelial cell (EC) is the primary target for Rickettsia conorii (RC) in Mediterranean spotted fever (MSF). Clinical manifestations such as thrombosis and vasculitis are mediated by pathologic changes localized in blood vessels. To study the in vivo endothelial injury induced by RC, markers of endothelial damage, including circulating EC (CEC), plasmatic thrombomodulin (TM), and von Willebrand factor (vWF), were investigated in 12 patients with MSF. CEC were counted in whole blood by a new immunomagnetic separation assay using a specific anti-EC antibody, S-Endo 1. Plasmatic TM and vWF antigens were measured by enzyme-linked immunosorbent assay. High levels of CEC and cell fragments were found in patients with a severe or malignant form of MSF. Sequential studies of CEC showed a decrease from 162 +/- 454 cells/mL before treatment to 6 +/- 7 cells/mL during treatment and recovery. Mean plasma TM and vWF levels that were also elevated before therapy (TM, 106 +/- 27 ng/mL; vWF, 420% +/- 164%) decreased progressively (TM, 55 +/- 43 ng/mL; vWF, 148% +/- 26%) during treatment. The measurement of cellular and molecular markers of vascular damage such as CEC, plasmatic TM, and vWF contributes to the definition of the Rickettsia-induced endothelial injury in vivo.

Antibodies, Monoclonal↗
PubMed1993

Determination of genome size and restriction pattern polymorphism of Rickettsia prowazekii and Rickettsia typhi by pulsed field gel electrophoresis.

Pulsed field gel electrophoresis (PFGE) of SmaI, MluI and SalI digested DNA was used to estimate genome size and perform restriction fragment length polymorphism analysis for Rickettsia prowazekii and Rickettsia typhi. We concluded that the genome of R. prowazekii and R. typhi consisted of a single chromosomal DNA. The total length of DNA of R. prowazekii was 1,106 +/- 54 kb and of R. typhi was 1,133 +/- 44 kb. It was possible to differentiate two strains of R. prowazekii, Breinl and EVir, by PFGE analysis after SalI digestion. Restriction fragment length polymorphism analysis did not reveal intraspecies differences between three human isolates and one Xenopsilla cheopis isolate of R. typhi.

DNA Restriction Enzymes↗
PubMed1993

Lack of pathotype specific gene in human Coxiella burnetii isolates.

Human Q fever, due to the obligate intracellular bacterium Coxiella burnetii may be acute or chronic. The acute form is rarely fatal, although the chronic form, mostly represented by chronic Q fever endocarditis, is severe and usually fatal in lack of appropriate treatment. A correlation between the human disease state and plasmid types has been described, and specific DNA sequences unique to each plasmid type and which would code for specific pathotypes have been characterized. Because this gene specificity of the pathogenesis was hypothesized only on a small number of isolates, we evaluated seven reference isolates and 30 recent C. burnetii isolates from France for which all clinical data were available using the polymerase chain reaction by employing two specific primer sets. Our studies indicate that the previously described CbhE' plasmid-gene is not unique to C. burnetii isolates associated with acute disease, which would mean that the hypothesis of the correlation between gene specificity and pathotype has to be revised.

Acute Disease↗
PubMed1993

Proteinase K-sensitive and filterable phagosome-lysosome fusion inhibiting factor in Afipia felis.

Afipia felis is one of the putative agents of cat scratch disease (CSD). Its intracellular location was previously demonstrated in tissue sections. It has been recently grown in human monocytes and in HeLa cells. We report that A. felis may infect human macrophages and the P 388 D1 murine macrophage cell line, yet is unable to grow in the cell-free culture medium. In both human macrophages and P 388 D1, the organisms multiply in a vacuole after active inhibition of phagosome-lysosome fusion (P-L) as demonstrated with cationized ferritin-labeled lysosomes. This P-L fusion inhibition is diffusable and is due to a filterable factor which is inactivated by protease digestion. The pathogenic role of A. felis in CSD may result from its ability to invade and multiply in macrophages.

Animals↗
PubMed1993

Comparison of western blot and microimmunofluorescence as tools for Lyme disease seroepidemiology.

Sera from a population of 212 farmers of the Puy de Dôme (Midlands of France) who are in close contact with Ixodes ricinus, the vector of Lyme disease in Europe, and sera from 100 urban blood donors from the nearly city of Clermont Ferrand were examined by microimmunofluorescence (MIF) for antibodies reacting with Borrelia burgdorferi. The results showed a higher seroprevalence of IgG > 1/100 in farmers (25%) than in blood donors (10%). Using western blot with antibody at a 1/200 dilution, and regarding sera as being positive if they contained IgG reactive with more than 5 bands, 93/212 farmers (44%) and 20% of blood donors were positive. Reactions with specific protein bands (94, 73, 30 and 21 KDa) by western blot were demonstrated in 83/212 sera from farmers (39%) and 16% of blood donors. Both methods showed a higher seroprevalence in the farmer population. Western blot is a sensitive and specific test for seroepidemiology but, in highly endemic areas, it is not diagnostic for active Lyme borrelliosis.

Adult↗
PubMed1993

Proposed tests for the routine identification of Rochalimaea species.

A study was conducted to establish tests for the routine identification of Rochalimaea species. Strains used were reference strains of Rochalimaea vinsonii and Rochalimaea quintana, and a type strain and six human isolates of Rochalimaea henselae. Rochalimaea species were confirmed to be gram-negative, oxidase-negative, non-motile, urease-negative, indole-negative, catalase-negative, glucose-nonfermenting organisms which failed to grow on MacConkey agar. Further testing of the organisms in a commercial identification system with the addition of hemin (100 micrograms/ml) to the medium revealed biochemical reactivity of the organisms not previously observed. The Voges-Proskauer reaction, tests for hydrolysis of hippurate and esculin, leucine arylamidase activity and the lactose test allowed identification and differentiation of the three species. Rochalimaea henselae was the only species with a positive lactose test and Rochalimaea quintana was the only species with a positive Voges-Proskauer reaction. Further studies are needed to confirm the validity of these tests for identification of Rochalimaea species.

Bacterial Typing Techniques↗