Bacteriologic and histologic studies of hepatic abscesses in cattle

Twenty-eight abscessed livers were collected from feedlot cattle at an abattoir; specimens were obtained from 49 abscesses for bacteriologic culture and for histologic examination. Cultural procedures included techniques to enumerate and isolate facultative and obligate anaerobic bacteria. Anaerobic bacteria were isolated from all 49 abscesses, whereas facultative bacteria were isolated from only 22. Mean bacterial counts for anaerobic and facultative bacteria were 3 X 10(8) and 8 X 10(8) bacteria/g of purulent material, respectively. Fusobacterium necrophorum, the only anaerobe isolated, was detected in 100% of the abscesses. Fusobacterium necrophorum biotype A was isolated from 57% of the abscesses (in pure culture from 75%), and F necrophorum biotype B was isolated from 47% of the abscesses (from 96% with mixed infections). Corynebacterium pyogenes was the predominant facultative bacterium isolated. Histologic changes in abscesses were qualitatively similar; abscesses were pyogranulomatous, with a necrotic center surrounded by zones of inflammatory tissue. However, the severity of lesions varied, depending on the F necrophorum biotype involved. Portal triad fibrosis and bile-duct proliferation were most severe in biotype A and mixed biotype B infections and less severe in abscesses from which biotype B was isolated in pure culture.