Establishment of a New Murine Model of Liver Abscess Induced by Fusobacterium Necrophorum Injected into the Caudal Vein

Anaerobic bacterial infection is often accompanied by abscess formation; however, few in vivo studies have been published with descriptive data specifically evaluating antimicrobial activity in the presence of abscesses. The aim of this study was to establish a murine model of anaerobic infection with abscess formation and to verify the utility of this model for evaluating the in vivo efficacy of an antimicrobial agent. A clinical isolate of Fusobacterium necrophorum was inoculated into the caudal vein of immunocompetent BALB/c mice at 10(8) c.f.u. per mouse. Changes in body weight, bacterial load and histopathology of key organs were evaluated. After inoculation, bacterial counts in the liver increased from 10(4) to 10(8) c.f.u. after 1-3 days, and liver abscess formation was observed on the day following infection. Abscess formation and bacterial growth were not observed in other organs. In this model, 3 days of treatment with 5 mg metronidazole kg(-1) eradicated F. necrophorum in the liver; however, a reduction in bacterial load was not observed with 0.05 mg metronidazole kg(-1). In this study, we established a novel murine model of F. necrophorum liver abscess via haematogenous infection that may be useful for investigating in vivo antimicrobial activity against anaerobic abscesses and understanding the pathogenesis of F. necrophorum infection.