The Fusobacterium Genus

Abstract

80 strains of fusiform bacilli from human and animal sources were divided into 2 groups by their biochemical and serological behavior. Group II is distinguished from group I by (a) its ability to produce approximately twice as great an acidity from carbohydrates, (b) its property of fermenting maltose and trehalose and (c) its failure to form indol, produce H2S and reduce nitrates. It is proposed that groups I and II be designated as separate species. Each of the 2 groups is made up of 2 definite subgroups or types. Anaerobic conditions were obtained by employing a jar-evacuation, hydrogen, catalyst (palladinized asbestos) method. Satisfactory agglutinating antigens were prepared with N/20 Na2HPO4 [center dot] 12H2O. The precipitin technique did not yield reliable results. All but 3 of the animal strains belonged to group I.[long dash]II. The morph. and colonial characteristics of the fusobacteria are variable, but conform in general to the groups I and II. The nature of the growths in broth constitutes a valuable criterion for differentiating the 2 groups group I produces a uniform turbidity, group II develops as a floccular sediment. The growth requirements are widely different. Aqueous potato extract is stimulating to the entire genus, but cysteine favors only group I, and glucose group II. Upon primary isolation all of the fusiform bacilli studied required a growth-promoting substance such as potato and, in addition, needed strictly anaerobic conditions. Both the nutritive and anaerobic requirements were greatly influenced by artificial cultivation. Bacterial variation within the genus was observed in the form of granular growth in broth and opaque colony on agar. The smooth group II colony is rhizoid. Spiral cells were observed on occasion, but bore no close resemblance to real spirochetes. They result from aging or cultivation under unfavorable conditions. Although lethal strains for laboratory animals were isolated, no evidence of an exo- or endotoxin was obtained.