Biomedical subjects

D Raoult

Publications and source records attributed to D Raoult.

At least 271 records · Page 15Linked to original sources

PubMed1997

Exposure of cats in southern Africa to Coxiella burnetii, the agent of Q fever.

Recently, the domestic cat has been implicated in numerous outbreaks of Q fever in humans. To determine if cats in southern Africa are infected with the agent of Q fever we tested sera from cats in South Africa and Zimbabwe by indirect fluorescence for antibodies reactive with phase II Coxiella burnetii antigen (Nine Mile strain). Reactive antibodies were detected at titres of > or = 1/40 in sera from cats in South Africa (1/52, 2%) and Zimbabwe (15/119, 13%). Our results indicate that cats in southern Africa are infected with C. burnetii and should be considered as sources of infection for humans.

Animals↗

PubMed1997

Domestic cats as indicators of the presence of spotted fever and typhus group rickettsiae.

Using indirect immunofluorescence assays, sera from cats in Zimbabwe (n = 119) and South Africa (n = 52) were found to contain antibodies reactive with Rickettsia conorii (34% and 19% respectively) and R. typhi (7% and 10% respectively). These results indicate that cats may become infected with members of the spotted fever and typhus groups of rickettsiae and that cats can, therefore, be used as indicators of the presence of these organisms.

Animals↗

PubMed1997

Study of the 16S-23S ribosomal DNA internal spacer of Coxiella burnetii.

The complete 16S-23S ribosomal DNA (rDNA) internal transcribed spacer (ITS) of 22 isolates of the obligate intracellular bacterium Coxiella burnetii, the agent of Q fever, were amplified by the polymerase chain reaction (PCR) and sequenced using an automated laser fluorescent DNA sequencer. The ITS measured 497 base pairs (bp) and encoded isoleucine-tRNA and alanine-tRNA. The comparison of the sequence alignments of the 22 C. burnetii strains revealed very high levels of sequence similitary (> 99%) although they had different geographic origins and phenotypic characteristics. Sequencing of the 16S-23S rDNA ITS of C. burnetii could be utilized for identification of the bacterium but is not applicable to studies of epidemiology, virulence and taxonomy.

Animals↗

PubMed1997

rpoB sequence analysis as a novel basis for bacterial identification.

Comparison of the sequences of conserved genes, most commonly those encoding 16S rRNA, is used for bacterial genotypic identification. Among some taxa, such as the Enterobacteriaceae, variation within this gene does not allow confident species identification. We investigated the usefulness of RNA polymerase beta-subunit encoding gene (rpoB) sequences as an alternative tool for universal bacterial genotypic identification. We generated a database of partial rpoB for 14 Enterobacteriaceae species and then assessed the intra- and interspecies divergence between the rpoB and the 16S rRNA genes by pairwise comparisons. We found that levels of divergence between the rpoB sequences of different strains were markedly higher than those between their 16S rRNA genes. This higher discriminatory power was further confirmed by assigning 20 blindly selected clinical isolates to the correct enteric species on the basis of rpoB sequence comparison. Comparison of rpoB sequences from Enterobacteriaceae was also used as the basis for their phylogenetic analysis and demonstrated the genus Klebsiella to be polyphyletic. The trees obtained with rpoB were more compatible with the currently accepted classification of Enterobacteriaceae than those obtained with 16S rRNA. These data indicate that rpoB is a powerful identification tool, which may be useful for universal bacterial identification.

DNA-Directed RNA Polymerases↗

PubMed1997

Use of amplification and sequencing of the 16S rRNA gene to diagnose Mycoplasma pneumoniae osteomyelitis in a patient with hypogammaglobulinemia.

A splenectomized patient with hypogammaglobulinemia who was hospitalized because of a high-grade fever subsequently developed osteomyelitis. Although pus cultures were repeatedly sterile, polymerase chain reaction (PCR) analysis with use of 16S rRNA gene primers with a broad specificity detected bacterial DNA in pus samples. Subsequent nucleotide base determination of the amplified DNA demonstrated that the detected DNA was derived from Mycoplasma pneumoniae. The results were confirmed by a PCR assay with use of M. pneumoniae-specific primers. Our findings confirm the usefulness of 16S rRNA gene amplification and analysis in the rapid and specific diagnosis of infectious osteomyelitis and reaffirm the role of such methods in detecting fastidious or uncultivable pathogens.

Adult↗

PubMed1997

A focus of tick-borne relapsing fever in southern Zaire.

Relapsing fevers occur worldwide and are characterized by recurrent episodes of fever and spirochetemia. In central, eastern, and southern Africa, the disease is often caused by Borrelia duttonii, which is transmitted by the soft tick Ornithodors moubata. We conducted a field investigation in September 1994 at a hospital in Mitwaba, southern Zaire, which was the only medical facility within 150 km. The introduction of a rapid blood-smear staining technique allowed us to demonstrate that 4.3%-7.4% of the 25-50 new outpatients seen each day had relapsing fever. Because of the absence of malaria in this area, these patients account for most of the febrile patients. The incidence of relapsing fever among all pregnant women in the maternity ward was estimated to be 6.4%, and this condition often led to maternal death or to spontaneous abortion. The 16S rRNA gene of B. dutonii was sequenced after the spirochete was isolated from patients' blood samples and directly from Ornithodoros tick vectors. In this region of Africa, relapsing fever should now be considered an important public health priority.

Animals↗

PubMed1997

Rickettsia conorii infection enhances vascular cell adhesion molecule-1- and intercellular adhesion molecule-1-dependent mononuclear cell adherence to endothelial cells.

Leukocyte adherence to the endothelium is an essential component of the inflammatory response during rickettsial infection. In vitro, Rickettsia conorii infection of endothelial cells enhances the expression of adhesive molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in a time- and dose-dependent manner. Rickettsial lipopolysaccharide does not seem to be involved, because polymyxin B does not reduce their expression. The intracellular presence of the organism and de novo host protein synthesis are required for expression of cell adhesive molecules, since rickettsial inactivation by formol and pretreatment of cells with cycloheximide inhibits an increase in expression. The contribution of interleukin-1alpha (IL-1alpha) to this endothelial adhesive phenotype was shown by inhibitory experiments 8 and 24 h after infection with IL-1 receptor antagonist and IL-1alpha blocking antibodies. Enhanced adherence of mononuclear cells to infected endothelial cells involved VCAM-1- and ICAM-1-dependent mechanisms at the late phase of the inflammatory response. This endothelial adhesive phenotype may constitute a key pathophysiologic mechanism in R. conorii-induced vascular injury.

Animals↗

PubMed1997

Oral treatment of Staphylococcus spp. infected orthopaedic implants with fusidic acid or ofloxacin in combination with rifampicin.

Oral therapy of staphylococcal infection of orthopaedic implants with 900 mg/day rifampicin combined with either 1.5 g/day fusidic acid for 5 days followed by 1 g/day thereafter, or 600 mg/day ofloxacin was compared. Patients with an infected hip were treated for 6 months, with removal of any unstable prosthesis after 5 months' treatment and those with an infected knee prosthesis were treated for 9 months, with removal of the prosthesis after 6 months of treatment. Patients with infections of other type of bone implants were treated for 6 months with removal of the implant after 3 months of treatment, if necessary. Cure was defined as the absence of clinical, microbiological and radiological evidence of infection 12 months after completion of treatment. The treatment of 46 of the 52 included in the study was evaluated for safety and that of 42 was assessed for efficacy. Overall treatment was successful for 11 (55%) of 20 patients treated with rifampicin and fusidic acid group and for 11 (50%) of the 22 treated with rifampicin and ofloxacin. Treatment failed in four cases in each treatment group because of persistent infection. One patient given rifampicin and fusidic acid and three patients given rifampicin and ofloxacin failed treatment because of relapse. Superinfection led to failure in the remainder and was due to staphylococci in all but one case in which Acinetobacter calcoaceticus var. anitratus was isolated. There were no side effects related to study treatment. Oral treatment with rifampicin combined with fusidic acid may be a suitable alternative to the combination of rifampicin and ofloxacin for treating implant infections due to Staphylococcus spp. either when the patient is intolerant to quinolones or when the infecting organism is resistant to these drugs.

Administration, Oral↗

PubMed1997

Bacteriostatic and bactericidal activity of levofloxacin against Rickettsia rickettsii, Rickettsia conorii, 'Israeli spotted fever group rickettsia' and Coxiella burnetii.

Levofloxacin, the L-isomer of ofloxacin, is approximately twice as active as ofloxacin against most Gram-positive and Gram-negative bacteria, and has improved intracellular pharmacokinetic and pharmacodynamic properties. The present work deals with the in-vitro activity of levofloxacin against the obligate intracellular bacteria Rickettsia rickettsii, Rickettsia conorii, 'Israeli spotted fever group rickettsia' (Israeli SFGR) and Coxiella burnetii. Fluoroquinolones, including ofloxacin, have previously been shown to be bacteriostatic against Rickettsia spp. and C. burnetii in vitro. They are reliable alternatives to tetracycline therapy for Mediterranean spotted fever, scrub typhus and acute Q fever. Levofloxacin was bacteriostatic against R. rickettsii, R. conorii and the Israeli SFGR at concentrations of 0.5-1 mg/L, as determined by both a plaque assay and a dye uptake assay. It was also bacteriostatic against C. burnetii isolates, including the Nine Mile, Priscilla and Q212 strains, at concentrations of 0.5-2 mg/L, as determined using the shell vial assay. Overall, levofloxacin could inhibit rickettsial growth at concentrations equal to or half of those necessary for growth inhibition by ofloxacin. Levofloxacin was not bactericidal against C. burnetii at concentrations up to 4 mg/L.

Anti-Infective Agents↗

PubMed1997

Stenotrophomonas africana sp. nov., an opportunistic human pathogen in Africa.

A gram-negative bacterium was isolated from a cerebrospinal fluid sample from an HIV-seropositive Rwandan refugee with primary meningoencephalitis. This Marseille-Goma sample B isolate, strain MGBT (T = type strain), was found to exhibit evolutionary homology with Stenotrophomonas maltophilia, as determined by a 16S rRNA gene sequence analysis, and this finding was reflected by similar phenotypic traits. MGBT could, however, be distinguished from the S. maltophilia type strain by using a number of biochemical and physiological tests, and a genotypic analysis of the two strains in which DNA homology was used revealed only 35% homology between them. Furthermore, the antibiotic susceptibility of MGBT was restricted to netilmicin, ciprofloxacin, trimethoprim-sulfamethoxazole, and colimycin. On the basis of these results we propose that MGBT is a representative of a new species in the genus Stenotrophomonas, Stenotrophomonas africana.

Bacteriological Techniques↗

PubMed1997

Citrate synthase gene comparison, a new tool for phylogenetic analysis, and its application for the rickettsiae.

Using PCR and an automated laser fluorescent DNA sequencer, we amplified and sequenced a 1,234-bp fragment of the citrate synthase-encoding gene (gltA) of 28 bacteria belonging to the genus Rickettsia. Comparative sequence analysis showed that most of the spotted fever group (SFG) rickettsiae belonged to one of two subgroups. The first subgroup included Rickettsia massiliae, strain Bar 29, Rickettsia rhipicephali, "Rickettsia aeschlimanni," and Rickettsia montana, which have been isolated only from ticks. The second subgroup was larger and included the majority of the human pathogens and also rickettsiae isolated only from ticks; the members of this subgroup were strain S, Rickettsia africae, "Rickettsia monglotimonae," Rickettsia sibirica, Rickettsia parkeri, Rickettsia conorii, Rickettsia rickettsii, the Thai tick typhus rickettsia, the Israeli tick typhus rickettsia, the Astrakhan fever rickettsia, "Rickettsia slovaca," and Rickettsia japonica. The sequence analysis also showed that the tick-borne organisms Rickettsia helvetica and Rickettsia australis and the mite-borne organism Rickettsia akari were associated with the SFG cluster, that Rickettsia prowazekii and Rickettsia typhi, two representatives of the typhus group, clustered together, and that Rickettsia canada; Rickettsia bellii, and the AB bacterium probably represent three new groups. We compared the phylogenetic trees inferred from citrate synthase gene sequences and from 16S ribosomal DNA (rDNA) sequences. For rickettsial phylogeny, the citrate synthase approach was more suitable, as demonstrated by significant bootstrap values for all of the nodes except those in the larger subgroup defined above. We also compared phylogenetic analysis results obtained in a comparison of the sequences of both genes for all of the representatives of the domain Bacteria for which the gltA sequence was determined. We believe that comparison of gltA sequences could be a complementary approach to 16S rDNA sequencing for inferring bacterial evolution, especially when unstable phylogenetic models are obtained from ribosomal sequences because of high levels of sequence similarity between the bacteria studied.

Animals↗

PubMed1997

Rickettsia aeschlimannii sp. nov., a new spotted fever group rickettsia associated with Hyalomma marginatum ticks.

We formally propose the name Rickettsia aeschlimannii sp. nov. for a new spotted fever group (SFG) rickettsia, strain MC16T, isolated from Hyalomma marginatum marginatum ticks collected in Morocco. This organism shows a typical rickettsial morphology when analyzed by electron microscopy. After characterization by serotyping, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western immunoblotting, PCR-restriction fragment length polymorphism (RFLP), pulsed-field gel electrophoresis, and 16S rDNA sequencing, this organism was found to be different from all of the recognized SFG rickettsiae. Identical PCR-RFLP profiles have, however, been found in H. marginatum marginatum from Portugal and H. marginatum rufipes from Zimbabwe, which suggests that the distribution of this rickettsia reaches from the Mediterranean to southern Africa.

Animals↗

PubMed1997

Reassessment of the taxonomic position of Rickettsiella grylli.

We determined the 16S rRNA gene sequence of Rickettsiella grylli, an intracellular parasite of Gryllus bimaculatus and related species of crickets. Phylogenetic inferences made from alignment of this sequence with the sequences of other bacteria demonstrated that R. grylli is most closely related to Coxiella burnetii and Legionella species in the gamma subclass of the phylum Proteobacteria. R. grylli was previously thought to be related to members of the order Rickettsiales, but the representatives of this order have been shown to be members of the alpha 1 subclass of the Proteobacteria. Our results indicate that R. grylli should be removed from the order Rickettsiales.

Animals↗

PubMed1997

Coxiella burnetii: the 'query' fever bacterium. A model of immune subversion by a strictly intracellular microorganism.

Although substantial progress occurred in the knowledge of Coxiella burnetii during the past years, the pathophysiology of Q fever is still obscure. Emerging evidence from clinical investigations suggested that certain disorders of cell-mediated immunity play a pivotal role in Q fever and especially in its chronic form. This review analyses the potential strategies that C. burnetii, a strictly intracellular pathogen, use to divert microbicidal mechanisms of macrophages and to depress protective T-cell mediated immunity. The role of monocytes in the induction of Q fever is specifically discussed.

Humans↗

PubMed1997

Guinea pig model for Staphylococcus aureus native valve endocarditis.

We present a new experimental model of Staphylococcus aureus infective endocarditis in guinea pigs. Permanent aortic valve damage was produced by electrocoagulation after catheterization of the right carotid artery, which allowed avoidance of the intracardiac catheter to produce cardiac vegetations. Our model closely mimics pathological mechanisms of native valve endocarditis.

Animals↗

PubMed1997

CD4+ T-cell lymphopenia in Q fever endocarditis.

Valvular endocarditis is the most serious complication of chronic Q fever, an infectious disease due to Coxiella burnetii. Although its pathogenesis is poorly understood, the role of the immune system has been evoked. The aim of this study was to investigate lymphocyte subsets in the peripheral blood of infected patients by analyzing the distribution of T- and B-lymphocyte subsets. Since various infectious diseases have been found to be associated with modified antigen expression, we also measured the antigen density of the main lymphocyte markers by quantitative flow cytometry. The absolute values of CD3+ T cells and CD19+ B cells were lower in infected subjects than in controls. The decrease in the CD4+ T-cell count was more pronounced than that in the CD8+ T-cell count, leading to a significantly lower CD4/CD8 ratio in patients. The decreases in CD4+ T cells and CD19+ B cells were correlated with levels of C. burnetii-specific immunoglobulin G, showing that CD4+ lymphopenia is related to the activity of chronic Q fever. Quantitation of antigen expression on lymphocytes showed that CD3, CD4, CD8, and CD19 were expressed similarly in patients and controls. In contrast, CD2 and CD11a expression levels, which are both related to naive and memory phenotypes, were modified in patients. The study of CD45RO and CD45RA expression by CD4+ T cells provided evidence that lymphopenia preferentially affected unprimed lymphocytes.

Adult↗

PubMed1997

Serological cross-reactions between Coxiella burnetii and Legionella micdadei.

Coxiella burnetii and Legionella micdadei are both gram-negative bacteria potentially responsible for identical clinical syndromes resembling upper respiratory infections. These infections, quite common in immunocompromised patients, are usually diagnosed by serology with a microimmunofluorescence assay. We found that 34.5% of Q fever patients had a significant titer of antibodies against L. micdadei. Cross-reactions involved immunoglobulin G antibodies and were demonstrated by a cross-adsorption study and protein immunoblotting. Western blot analysis performed after treatment with proteinase K indicated that cross-reactions were probably due to both protein and lipopolysaccharide antigens. It is critical that the existence of this cross-reaction be recognized, as misdiagnosis of either condition may lead to incorrect and ineffective treatment.

Antibodies, Bacterial↗

PubMed1997

Afipia clevelandensis antibodies and cross-reactivity with Brucella spp. and Yersinia enterocolitica O:9.

Afipia clevelandensis is a recently described gram-negative bacterium whose potential pathogenic role in human disease is under investigation. Only one strain, from the pretibial lesion of a patient hospitalized with necrotizing pancreatitis for 5 months, has been isolated. Using an indirect immunofluorescence assay to detect anti-A. clevelandensis antibodies, we found a seroprevalence of 1.5% among 30,194 sera routinely submitted for laboratory diagnosis of rickettsial diseases. However, among the 52 patients who were clinically evaluable and who exhibited detectable antibodies against A. clevelandensis, 42% were eventually diagnosed as certainly or probably having brucellosis and 15% were eventually diagnosed as certainly or probably having Yersinia enterocolitica O:9 infection, which is the serotype most often encountered in Europe. Western immunoblotting and cross-adsorption tests showed that an 11.5-kDa proteinase K-labile band and a 21-kDa proteinase-stable band, presumably lipopolysaccharide, were responsible for cross-reactivity among A. clevelandensis, Brucella abortus, and Y. enterocolitica O:9. Other diagnoses included nosocomial infections and various community-acquired diseases for which the role of A. clevelandensis remains undefined. Physicians and clinical microbiologists should be aware of this cross-reactivity in future assessments of the role of A. clevelandensis in human pathology.

Aged↗