Failure of azithromycin in treatment of Brill-Zinsser disease.

Two patients suffering from Brill-Zinsser disease were treated with azithromycin, which did not prove effective. Rickettsia prowazekii, the agent causing Brill-Zinsser disease, cannot be treated with azithromycin. Both patients had epidemiological features consistent with and a clinical course typical of the disease. The diagnosis of Brill-Zinsser disease was serologically confirmed.