Les Rickettsies : caractères microbiologiques, identification, relations avec les arthropodes, pathogénie des infections (2e partie)

Bacteria classified within the Rickettsia genus are small bacilli associated with arthropods. Their identification is made difficult by their strict intracellular growth. As a consequence, the diagnosis of rickettsioses was often delayed. Before the molecular era, the identification of species of the Rickettsia genus relied on the few phenotypic characters which they expressed. Of these, the most efficient and most widely used was mouse serotyping that was based on the antigenic specificities of each species. With the advent of the PCR and sequencing, and thanks to the development of a new cell culture technique derived from viral cultures, the diagnosis of rickettsioses has known a decisive progress over the last 20 years. In addition, the recent development of discriminatory identification methods has facilitated the taxonomic classification of Rickettsia isolates. This made it possible to identify several dozens of new Rickettsia and to initiate the study of the physiopathological aspects of rickettsioses.