Bartonella

BARTONELLA

Bartonella species differ from rickettsiae in that they can be cultured on artificial media.By 16s ribosomal comparison they are actually more closely related to Brucella than to rickettsiae. Bartonella quintana, the best known species of this genus, causes trenchfever, which has a worldwide distribution. The name derives from its prominence in thetrenches of World War I. This disease has a reservoir in humans, and its vector is the body louse. Most cases are mild or subclinical. When symptomatic, the patient has sudden on-set of chills, headache, relapsing fever, and a maculopapular rash on the trunk and ab-domen. Illness can last for 14 to 30 days and the disease is suggested by a history of louse contact. More recently, B. quintana bacteremia and endocarditis have been described in homeless alcoholic men in both France and the United States. The diagnosis can be made by culturing the organism on special agar medium or by demonstrating seroconversion.

Bartonella bacilliformis, a related organism, is the cause of acute Oroya fever and, inits chronic phase, verruga peruana. Infections with this agent are seen only in South America at intermediate altitudes, in keeping with the distribution of its sandfly vector.

Another species, Bartonella henselae, has been associated with a number of diseases, the most common of which is cat scratch disease. Cat scratch disease is a febrile lym-phadenitis with systemic symptomatology that sometimes persists for weeks to months. Approximately 24,000 cases occur in the United States each year. The disease is thought to be transmitted by cat scratches or bites and perhaps by the bites of cat fleas. Manifesta-tions may include skin rashes, conjunctivitis, encephalitis, and prolonged fever. Occasion-ally, retinitis, endocarditis, and granulomatous or suppurative hepatosplenic and osseous lesions have also been seen. B. henselae has been isolated directly from the blood of cats, although the latter do not appear ill. It can also be isolated from human blood, lymph nodes, and other materials using special media. Organisms can sometimes be directly demonstrated in infected tissues by using the Warthin–Starry silver impregnation stain. A serologic response to B. henselae antigens is the primary method of diagnosis. Azithromycin or erythromycin may reduce the duration of lymph node enlargement and symptoms.

Bacillary angiomatosis, a proliferative disease of small blood vessels of the skin and viscera, seen in acquired immunodeficiency syndrome (AIDS) patients and other im-munocompromised hosts, has been associated with Bartonella by molecular methods. The PCR  was used to amplify ribosomal RNA gene fragments directly from tissue samples. Sequence analysis of DNA transcribed from these fragments pointed to the Bartonella genus. Subsequently, both B. henselae and B. quintana have been iso-lated from AIDS patients with bacillary angiomatosis. Other conditions seen primarily in AIDS patients, such as peliosis hepatis and bacteremia with fever, have also been associ-ated with B. henselae. Bartonella infections in AIDS and other immunosuppressed patients, as well as the bacteremia observed in alcoholic and homeless men, generally respond to prolonged courses of erythromycin. Bartonella endocarditis usually requires valve replacement as well.