The natural history of murine intra-abdominal abscess formation

W. G. Cheadle, M. J. Hershman, J. D. Pietsch, W. A. Logan and H. C. Polk Jr
Price Institute of Surgical Research, Department of Surgery, University of Louisville, School of Medicine, KY 40292.

We determined the natural history of experimental abscess formation and had a secondary interest in the effect of muramyl dipeptide. Swiss-Webster mice were injected intraperitoneally with autoclaved mouse fecal suspension and either Bacteroides fragilis (10(8) colony-forming units [cfu]/mL) alone or Escherichia coli (10(4) cfu/mL), enterococcus (10(3) cfu/mL), and B fragilis (10(5) cfu/mL) after pretreatment with muramyl dipeptide or saline solution. All deaths occurred within 48 hours of injection and surviving mice, including those bearing abscesses, appeared to be healthy throughout the study. The number of mice with abscesses and the number of abscesses per group were at their maximum at two to four weeks. Groups with live bacteria had a substantial reduction in the number of abscesses between eight and 26 weeks, compared with two- and four-week values. Manual rupture of palpably large eight-week-old abscesses in 21 mice produced only one death and at autopsy two weeks later, all of the mice showed multiple smaller abscesses. Abscess formation appeared to be beneficial and the natural history of such may include spontaneous resolution without mortality.