Isolation and characterization of an Ehrlichia sp. from a patient diagnosed with human ehrlichiosis

Abstract

A new disease was recognized in the United States in 1986. The etiologic agent, although not previously isolated from a human, appeared to be serologically related to Ehrlichia canis, a canine leukotropic rickettsia. We obtained blood specimens from 27 febrile patients with a history of tick exposure. Leukocytes from 24 patients not treated with tetracycline were placed onto a monolayer of DH82 cells. We performed indirect immunofluorescence on sera from all 27 febrile patients as well as sera from 12 patients with previously diagnosed ehrlichiosis. Intracytoplasmic inclusions were first observed in culture 35 days after the addition of infected blood from one patient. Partial sequencing of the rRNAs from the human isolate and E. canis indicated that they are 98.7% related. Positive indirect immunofluorescence reactions to the human isolate were obtained for all 12 previously diagnosed patients and for 33% of the 27 febrile patients. Two patients were seropositive for the human isolate but not for E. canis. No sera were positive for E. canis and negative for the human isolate. We report the isolation of a previously unrecognized Ehrlichia sp. that appears to be the etiologic agent of human ehrlichiosis. Serologic data (range of antibody titers, 256 to 32,768) in combination with rRNA sequencing indicated that the newly isolated Ehrlichia sp. is similar, but not identical, to E. canis.

Ehrlichiasecretes Etf-1 to induce autophagy and capture nutrients for its growth through RAB5 and class III phosphatidylinositol 3-kinase

“…9,43 HEK293 cells (ATCC, CRL-1573) and canine histiocytic leukemia DH82 cells were cultured in DMEM (Dulbecco's minimal essential medium; Mediatech, 10-013-CV) supplemented with 10% fetal bovine serum and 2 mM L-glutamine. 1 Cultures were incubated at 37 C under 5% CO 2 in a humidified atmosphere.…”

“…Ehrlichia chaffeensis, a Gram-negative obligatory intracellular bacterium in the family Anaplasmataceae, primarily infects monocytes and macrophages in mammals and causes the emerging tick-borne zoonosis called human monocytic ehrlichiosis. [1][2][3] This serious and sometimes fatal disease is characterized by fever, headache, myalgia, thrombocytopenia, leukopenia, and elevated liver enzyme levels. [3][4][5] One fundamental virulence factor of microbial pathogens is "nutritional virulence," 6 i.e., the ability to acquire nutrients for pathogen proliferation in competition with hosts and possible other microbes.…”

Unique macrophage and tick cell-specific protein expression from the p28/p30-outer membrane protein multigene locus in Ehrlichia chaffeensis and Ehrlichia canis

“…Several emerging tick-borne ehrlichial diseases have been reported in recent years that impact humans and animal health (Dumler et al ., 2001;Pantanowitz et al ., 2002). These emerging diseases included the human monocytic and granulocytic ehrlichiosis caused by Ehrlichia chaffeensis and Ehrlichia ewingii , respectively, and the human granulocytic anaplasmosis caused by Anaplasma phagocytophilum (Dawson et al ., 1991;Chen et al ., 1994a;Buller et al ., 1999). Ehrlichia canis has been identified as a major cause of tick-borne infections in dogs in nearly all parts of the world for several decades (Buhles et al ., 1974;Keefe et al ., 1982).…”

Determination of the genome size of Ehrlichia spp., using pulsed field gel electrophoresis

“…This could explain why only few genes were cloned and sequenced and why no information about the organization of the ehrlichial genome is currently available. Several ehrlichial isolates have recently been adapted to in vitro culture allowing a more detailed study of this genus [4,5]. The purpose of this work was the genome size determination for the representatives of three ehrlichial genogroups, namely E. sen-netsu, E. risticii, E. cha¡eensis and the HGE agent using pulse ¢eld gel electrophoresis (PFGE).…”