title: Fine structural characterisation of a Rickettsia-like organism in human platelets from patients with symptoms of ehrlichiosis.
abstract: Since 1982, Ehrlichia platys infection has been diagnosed in canines from Venezuela by the use of buffy coat smears. In 1992, ehrlichia-like bodies were observed in platelets from a severely ill girl by light microscopy. The patient was seropositive to E. chaffeensis by the indirect fluorescent antibody test (IFAT). Tetracycline was administered and the patient recovered. More than 400 cases with such intra-platelet organisms have been studied at this laboratory over the past 6 years, and all the patients had a good response to the treatment. To determine whether the organisms in human blood platelets were truly platelet ehrlichiae, IFAT and transmission electron microscopy (TEM) studies were undertaken in four patients. Light microscopic examination of blood samples revealed the dense organism inside platelets, and a great reactivity of the blood cells. Sera from the four patients were seronegative against E. chaffeensis and E. platys antigens. Three of four samples contained the intra-platelet organisms when examined by TEM. Electron microscopy showed platelets with vacuoles containing pleomorphic organisms. These organisms had a thickened membrane, an electron-translucent inner area and an electron-dense granular component in the periphery. An abundant electron-dense material was observed surrounding them. The ultrastructure of such micro-organisms has not been reported previously, Based on the similarity of many of their characteristics with rickettsiae, we suggest that the microorganisms found in the present study might belong to the family Rickettsiaceae.
authors.affiliation: Unidad de Investigaciones Clinicas, Facultad de Ciencias Veterinarias, Universidad del Zulia, Maracaibo.
authors.forename: Cruz
authors.initials: C
authors.lastname: Arraga-Alvarado
authors.affiliation: Instituto de Investigaciones Biologicas, Facultad de Medicina, Universidad del Zulia, Maracaibo.
authors.forename: Maria
authors.initials: M
authors.lastname: Palmar
authors.affiliation: Unidad de Investigaciones Clinicas, Facultad de Ciencias Veterinarias, Universidad del Zulia, Maracaibo.
authors.forename: Omaira
authors.initials: O
authors.lastname: Parra
authors.affiliation: Unidad de Microscopia Electronica, Universidad Nacional Experimental Francisco de Miranda, Coro, Venezuela.
authors.forename: Pedro
authors.initials: P
authors.lastname: Salas
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001792:Blood Platelets / Q000382:microbiology* / Q000648:ultrastructure; D004285:Dogs; D004536:Ehrlichia / Q000145:classification / Q000276:immunology / Q000648:ultrastructure*; D016873:Ehrlichiosis / Q000382:microbiology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007223:Infant; D008854:Microscopy, Electron
chemical_list: D000907:Antibodies, Bacterial