Characteristics of Fusobacterium ulcerans, a new and unusual species compared with Fusobacterium varium and Fusobacterium mortiferum

Fusobacterium ulcerans is a newly described obligately anaerobic Gramnegati ve, non-spore-forming rod [1] that has been isolated from tropical ulcers. Two morphotypes were described: one resembling Fusobacterium varium and the other Fusobacterium mortiferum [1]. Because of the weak or negative fermen tation reactions of most fusobacteria, the standard carbohydrate tests used for identification of anaerobe organisms are of little use for identificat ion, and other rapid and simple methods are needed. We characterized eight F. ulcerans strains using conventional biochemical testing. We further anal ysed these strains by PCR employing a single non-specific primer AP3 and by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of whole cell proteins. PCR using a self-designed pair of primers for the amplification of the spac er (intergenic) region between the 16S and 23S rRNA genes, led to the devel opment of genetic markers for species identification. All F. ulcerans clini cal isolates appeared very similar to each other in all the test parameters , but were distinctly different from the type strains of the two phenotypic ally similar species, F. mortiferum and F. varium. High similarity in PCR- and protein-profiles also raise the possibility that all these F. ulcerans strains came from one clone. We noted significant differences among the str ains of F. mortiferum and F. varium. (C) 1999 Academic Press.