Differentiation Between Fievre Boutonneuse and Rocky Mountain Spotted Fever by Means of Complement Fixation.

1993

J Bacteriol

Using pulsed-field gel electrophoresis, we studied the chromosomes of spotted fever group rickettsiae. We digested the DNA of 16 species currently known to belong to this group with SmaI, EagI, and BssHII. The genome size of 13 rickettsiae was between 1,200 and 1,300 kb. "Ricketisia massiliae" and "R. helvetica" genome sizes were 1,370 and 1,397 kb, respectively, and that ofR. bellii was 1,660 kb. It was possible to obtain distinctive patterns for each species, but in R. conorii, 10 isolates exhibited the same profiles, showing that pulsed-field gel electrophoresis is a good interspecies identification tool. We achieved a phylogenetic analysis of these bacteria by using the Dice coefficient and UPGMA and Package Philip programming. We established a dendrogram of the genetic relationships between the different species showing the existence of a cluster in the spotted fever group rickettsiae including R. conorii, R. rickettsii, R. parkeri, R. sibirica, "R. africae," "R.slovaca," Thai tick typhus rickettsia, and Israeli tick typhus rickettsia. We located three genes previously cloned and sequenced (genes encoding the R. rickettsii surface proteins of 120 and 190 kDa and the R. prowazekii citrate synthase gene), using Southern hybridization. The genes encoding citrate synthase and the surface protein of 190 kDa were usually located on the same band, and it is hypothesized that they are relatively close on the chromosome.The family Rickettsiaceae comprises several genera including the genus Rickettsia, which is subdivided into three groups: typhus, scrub typhus, and spotted fever group (SFG) rickettsiae. SFG rickettsiae have been grouped taxonomically on the basis of morphological, ecological, and antigenic criteria. These bacilli are gram-negative short rods, 0.3 to 0.5 pum in diameter and 0.8 to 2.0 pum in length (sometimes longer when cell division is impaired), which retain basic fuchsin when stained by the method of Gimenez (28) and which grow both in the nucleus and in the cytoplasm of the host cells (60). They are transmitted to humans by infectedarthropod bites or feces.The usual identification methods used in bacteriology are not applicable for rickettsiae because of their strictly intracellular position. The actual classification of SFG rickettsiae is exclusively based on mouse serotyping (41). The antigenic determinant of this serotyping is constituted by two major envelope proteins of high molecular weight called rOmp A and rOmp B (26). In fact, this method allows the identification of new isolates, but no information on the relationships between the different strains is given. It is necessary to define strict criteria of classification, because with the development of a new cell culture isolation technique (the shell vial technique) (36) over the past few years, there has been detection of new isolates everywhere in the world, both from ticks ("Rickettsia massiliae" in the south of France [6,7], MC6 in Morocco [37], GS in Greece [5], and "R. helvetica" in Switzerland [15]) and from humans ("R africae" in...

Section: Discussionmentioning

confidence: 99%

Genotypic identification and phylogenetic analysis of the spotted fever group rickettsiae by pulsed-field gel electrophoresis

Roux

1993

J Bacteriol

“…10 Various methods were used to study Rickettsia species but failed to provide easily reproducible identification tools, including complement fixation, toxinic neutralisation, SDS-PAGE, mouse serotyping, Western blot, development of monoclonal antibodies, and DNA-DNA hybridization. [11][12][13][14][15][16][17] As a consequence, although initially discovered in the early XX th century, Rickettsia sp. remained badly known until the 1990s and the introduction of molecular tools, and still are a matter of debate, in particular, in regarding their taxonomy.…”

Section: Introductionmentioning

confidence: 99%

Current Knowledge on Phylogeny and Taxonomy of Rickettsia spp.

Fournier

Annals of the New York Academy of Sciences

2009

119

Due to improved diagnostic methods and increased interest, the number of representatives of the genus Rickettsia has increased dramatically over the past 20 years, with 25 currently validated species. These arthropod-associated intracellular bacteria are now recognized in all parts of the world. The comparison of the phylogenic organizations obtained from the study of several genes with different functions, and more recently from genomic sequences, provided basis to establish a reliable taxonomy of the bacteria induded in the genus Rickettsia. These data were incorporated into polyphasic consensus guidelines that provide clear recommendations for the taxonomic classification and nomenclature of rickettsiae and rickettsial diseases.

“…Rickettsia conorii, the causative agent of Mediterranean spotted fever, when injected into guineapigs, protects the animals against challenge with Rickettsia rickettsii (Badger, 1933 ;Walker et al, 1984). Plotz et al (1944) subsequently showed that convalescent guinea-pig sera cross-reacted with antigen obtained from patients with Mediterranean spotted fever and Rocky Mountain spotted fever. The homologous titres with either antigen were significantly higher than the heterologous titres.…”

Section: Introductionmentioning

confidence: 99%

“…Plotz et al (1944) showed cross-reaction with R. conorii and R. rickettsii antigens in complement-fixation tests of sera from 15 patients, ten of whom had Rocky Mountain spotted fever and five Mediterranean spotted fever. Philip et al (1976) showed by immunofluorescence that sera from seven patients with Rocky Mountain spotted fever cross-reacted with R. conorii.…”

Section: Introductionmentioning

confidence: 99%

Cross-reaction of immune sera from patients with rickettsial diseases

Hechemy

Journal of Medical Microbiology

Fox

et al. 1989

Summary. Rickettsia rickettsii and Rickettsia conorii are the causative agents of two common and serious diseases, Rocky Mountain spotted fever and Mediterranean spotted fever, respectively. In patients naturally infected with either of these organisms, antibodies are produced which cross-react with antigens of the other so extensively that diagnostic tests usually cannot identify the causative agents. The results of this study indicate that serodiagnostic tests with antigen from one of these two organisms could be used to detect antibodies in patients with either of the two rickettsial diseases.