Fusiform bacilli and Vincent's spirilla are frequently credited with causing severe infections in the mouth and pharynx. During the last few years a number of cases have been reported in which fusospirochetal infection was considered responsible for severe pulmonary infection.
Since the first descriptions of the fusospirochetal organisms by Plaut1 in 1894 and Vincent2 in 1899, the organisms have been known to exist in the upper respiratory tract in the absence of any evidence of acute infection. Controversy still exists as regards the pathogenicity of these organisms. Smith3 has experimented at length and has reported that so-called fusospirochetal pulmonary infections are probably due to a symbiosis of a spirochete, a fusiform bacillus, a vibrio and a coccus. Lichtenberg, Werner and Leuck,4 who recently reviewed the literature in regard to authentic proof of the pathogenicity of these organisms and reported experimental data of their own, concluded that