Comparison of Fusobacterium necrophorum isolates from liver abscesses, ruminal walls, and ruminal contents of feedlot cattle

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Introduction
Liver abscesses occur most often in cattle layer of the ruminal wall, and diluted ruminal fed high grain diets.Abscessed livers com-contents were used for isolation of F. monly are found in 10-30% of feedlot cattle at necrophorum.slaughter.Fusobacterium necrophorum, a bacterium normally present in the rumen, is the In order to genetically compare the isoprimary causative agent of liver abscesses in lates, the technique of restriction fragment cattle.
length polymorphism (RFLP) analysis of The incidence of liver abscesses is generally higher in cattle with lesions of the rumen

Experimental Procedures
Samples of ruminal contents, ruminal wall slaughter, packed in ice, and transported to the laboratory.Swab samples of the pus from liver abscesses, homogenates of the epithelial ribosomal DNA or ribotyping was employed.Ribotyping involves the fingerprinting of chromosomal DNA restriction fragments that Isolates ranged form nine to 11. Isolates contain genes coding for 16S and 23S ribo-differing by one or more bands in their somal RNA (rRNA).Because the genes hybridization patterns were considered distinct coding for rRNA are highly conserved and strains (Figure 1). .most bacteria contain multiple copies of rRNA genes, a reasonable number of fragments are The ribotypic comparison of isolates from obtained after probing, and this allows dis-liver abscess and ruminal wall of the ame crimination among strains within the same animal showed that in eight out of nine cases, species.
F. necrophorum isolated from the ruminal wall Briefly, the procedure for ribotyping was 1).None of the ruminal content isolates as follows: chromosomal DNA was extracted matched with either the ruminal wall isolate or and digested with restriction endonucleases liver abscess isolate from the same animal.alone (EcoRI, EcoRV, SalI, and HaeIII) or in These results provide direct evidence for the combination (EcoRI and EcoRV).).Restric-proposed pathogenesis of liver abscesses.tion fragments were separated by gel electro-Prior to this, the only evidence available in phoresis and probed with a commercially support of this hypothesis was the statistical available 16 and 23S rRNA from E. coli.
correlation between the occurrence of liver Hybridization banding patterns of the isolates abscesses and ruminal pathology.were compared among isolates from all three locations within the same animal.Isolates The genetic similarity between the isolates were considered genetically different if even from liver abscesses and the isolates from the a single band was different between two iso-ruminal walls lends credence to the hypothesis lates with any of the restriction enzymes used that F. necrophorum of liver abscesses origito fragment the DNA.
nates from the rumen.The lack of genetic

Results and Discussion
Out of sets of liver abscesses, ruminal of strains.Therefore, chance is involved in walls, and ruminal content samples from 11 finding a match.Presumably, a single strain cattle, F. necrophorum was isolated from all among this multitude of strains penetrates and three locations from four animals, from liver colonizes the ruminal wall.abscesses and ruminal walls in five animals, and from liver abscesses and ruminal contents from two animals.This allowed comparison of nine isolates from liver abscesses and ruminal walls and six isolates from ruminal contents and liver abscesses.The number of major bands of DNA among the was identical to liver abscess isolates (Table similarity between ruminal content and liver abscess isolates is not surprising, because ruminal contents presumably have a multitude

Figure 1 .
Figure 1.Hybridization Patterns of Restriction Fragments of DNA from Fusobacterium necrophorum Isolates from the Ruminal Contents, Ruminal Wall, and Liver Abscesses Isolated from Animal No. 6. Lane MW Has Molecular Weight Markers.F. necrophorum from the Liver Abscesses Was Identical to That from Rumen Wall but Different from That of Rumen Contents.