Les Rickettsies : historique et actualité (1re partie)

In early part of the last century (1910) Ricketts and von Prowazek laid the foundation of modern rickettsiology. Their pioneering works eventually led to the recognition of new species and Rickettsials infections. As soon as Rickettsia are the first strictly intracellular bacteria described, its taxonomy gathered on the basis of this criterion : a great number of kinds of bacteria will be identified only with the advent of the sequencing and the discovery of molecular clocks such as ribosomal 16S RNA and cytochrome C. Many phenotypic criterion such as morphology, tests of complement, neutralization of toxins, mouse serotyping and SDS-page proved reliable. However, gene comparison (ompA, ompB and sca4) will make it possible to very precisely determine the species containing of the genus Rickettsia and to suggest a classification supported by high bootstrap values as well as antibiotics tests. Nevertheless, the phylogenetic position of species such Rickettsia helvetica, Rickettsia canadensis and Rickettsia bellii could not be given with precision, and the polyphasic analysis of the classification of the Rickettsia species based on genes concatenation associated with phenotypic characters available might be alternatives for Rickettsia phylogeny.