The pathogenesis of Enterococcus (Streptococcus)faecalis was studied in mice with E. faecalis intestinal overgrowth (1091010 per gram of cecum) induced by metronidazole and streptomycin treatment coupled with oral inoculation of E. faecalis. E. faecalis was recovered from the mesenteric lymph nodes, liver, and spleen; mortality was noted in 8 (13%) of 62 mice after 14 days of E.faecalis intestinal overgrowth. Light, immunofluorescent, and electron (scanning and transmission) microscopy of ileal tissue was used in an attempt to localize E. faecalis translocating across intestinal tissue. Dense coccal bacteria were observed in the intestinal lumen, and the epithelium appeared intact. Coccal bacteria were observed adherent to the microvillus border of the entire villous epithelium, including the deeper regions of the intestinal crypts. Immunofluorescence localized E. faecalis within columnar epithelial cells, lamina propria, submucosa, and muscularis externa (including the lumen of small vessels). Transmission electron microscopy localized coccal bacteria within vacuoles in the cytoplasm of intact epithelial cells. These results indicated that E. faecalis could translocate across an intact intestinal tract and cause systemic infection and death. In this model, the intestinal epithelial cell appeared to be a portal of entry in the pathogenesis of systemic E. faecalis infection.
Bibliographical noteFunding Information:
Received 27 October 1989; revised 12 January 1990. Grant support: National Institutes of Health (AI-23484) and the US Environmental Protection Agency Cooperative Agreement CR-814622 to the University of Minnesota. Reprints and correspondence: Dr. Carol L. Wells, Department of Laboratory Medicine and Pathology, Box 198 Mayo Building, University of Minnesota, Minneapolis, MN 55455.