First report of isolation of Fusobacterium varium from liver abscesses and ruminal and colonic epithelial tissues of feedlot cattle

Objective: Our objective was to isolate and determine prevalence of Fusobacterium varium in liver abscesses and the corresponding ruminal and colonic epithelial tissues and ruminal and colonic contents of feedlot cattle. Materials and Methods: A total of 96 intact liver abscess samples and matched ruminal and colonic tissues and contents from cattle, originating from feedlots that did not receive in-feed tylosin, were collected at slaughter. Liver abscesses and ruminal and colonic tissue were homogenized and then plated, before and after enrichment in lactate or lysine medium with selective antibiotics, onto blood agar and selective lactate or lysine agar for isolation of Fusobacterium and to determine prevalence and concentration. Putative colonies were tested by a quantitative PCR assay targeting the hgdA gene for species confirmation. Results and Discussion: None of the liver abscess samples yielded F. varium by direct plating; however, F. varium was isolated from 3 of 96 (3.1%) following enrichment of the homogenate in lactate or lysine medium. In contrast to liver abscesses, F. varium was isolated by direct plating from 27.1% (26/96) of ruminal epithelial and 3.1% (3/96) of colonic epithelial tissue homogenates. Overall, 10.1%, 77.1%, 44.8%, 86.5%, and 70.1% of liver abscess, ruminal, and colonic epithelial tissues and ruminal and colonic contents were positive for F. varium, respectively.