الكاتب: Multiple References

The agent of human granulocytic ehrlichiosis (HGE) was first described in 1994 in the upper Midwest of the United States (3, 4, 11) and then in other regions of this country (1, 19, 34) as well as in Europe (5, 23, 31, 32). The HGE agent, Ehrlichia phagocytophila (the agent of tick-borne fever of sheep and cattle in Europe), and Ehrlichia equi (the agent of equine and canine granulocytic ehrlichiosis) have recently been moved into the genus Anaplasma in the reorganized family Anaplasmataceae and unified in a single species, Anaplasma phagocytophilum (10, 12, 14). Wild rodents, deer, sheep, cattle, and horses are probable reservoirs of these bacteria (28), whereas ticks, including Ixodes scapularis and Ixodes pacificus in the United States and Ixodes ricinus in Europe, are considered major vectors for human transmission (9, 28). HGE is most often an asymptomatic to mild disease, but more-severe and even fatal cases have been described (4, 28). Doxycycline is the drug of choice for treating patients with HGE (1, 3, 4, 12, 13). However, safe alternatives to tetracyclines may be needed or desired for children younger than 8 years old because of the potential for tooth discoloration, for pregnant women because of the danger of bone toxicity for the fetus, for allergic patients, and for patients with gastric intolerance to these compounds (30). Failures in chloramphenicol treatment of patients with HGE have been reported (12), whereas the clinical usefulness of rifampin for treatment of pregnant women with HGE has been suggested (8). Only a few in vitro studies have assessed the antibiotic susceptibilities of this species (21, 22), and recent investigations have clearly delineated the diversity and heterogeneity of A. phagocytophilum strains of different geographic origins (2, 24). Here, we report the antibiotic susceptibilities of eight strains collected from human or animal sources in very different geographic areas of the United States.