Comparative changes in a rat liver abscess model induced with three Fusobacterium necrophorum strains.

Viable cultures of 3 bovine Fusobacterium necrophorum strains were inoculated into the hepatic portal veins of rats. The experimentally produced hepatic necrobacillosis lesions were examined beginning at 15 minutes after inoculation was done and continuing for 4 weeks. Fusobacterium necrophorum 2101 (FN 2101), a biotype A, was the most virulent; F necrophorum 2030 (FN 2030), a biotype AB, was of intermediate virulence; and F necrophorum 2035 (FN 2035), a biotype B, was the least virulent. Gross lesions were first observed at 2, 8, and 18 hours after inoculation in the FN 2101-, FN 2030-, and FN 2035-inoculated rats, respectively. Gross and histopathologic descriptions of the FN 2101 and FN 2030 hepatic necrobacillosis lesions were similar, but were markedly different from those of the FN 2035 lesions. Abscesses produced by FN 2101 and FN 2030 attained maximal diameter (1 cm) in the hepatic parenchyma. Subcapsular abscesses were produced by FN 2035 and attained a diameter of 2 to 3 mm (maximal).